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Immune checkpoint inhibitors have improved clinical outcomes in many malignancies, including renal cell carcinoma (RCC). Awareness of potential adverse events and effective management of these toxicities is critical to maximizing clinical outcomes. Pembrolizumab plus axitinib is approved as front-line treatment of advanced renal cell carcinoma (aRCC), making it the first checkpoint inhibitor and tyrosine kinase inhibitor combination approved for any malignancy. Given overlapping toxicities with this combination, the toxicity profile of each drug must be considered when assessing and managing toxicities in patients treated with pembrolizumab and axitinib. Use of online resources, including published guidelines from ASCO, the Immuno-Oncology Essentials Web site, and other organizations, can assist oncology and nononcology health care professionals to more effectively manage toxicities, maximize clinical outcomes, and improve quality of life for patients with aRCC. Herein, we describe a case of a patient with aRCC treated with pembrolizumab and axitinib, highlighting a systematic approach to toxicity management.

PURPOSE Metastatic mucosal melanoma responds poorly to anti–programmed cell death-1 (PD-1) monotherapy. Vascular endothelial growth factor (VEGF) has been shown to play an important immunosuppressive role in the tumor microenvironment. The combination of VEGF inhibition and PD-1 blockade provides therapeutic opportunities for patients refractory to either therapy alone. PATIENTS AND METHODS We conducted a single-center, phase IB trial evaluating the safety and preliminary efficacy of toripalimab, a humanized immunoglobulin G4 monoclonal antibody against PD-1 in combination with the VEGF receptor inhibitor axitinib in patients with advanced melanoma, including patients with chemotherapy-naïve mucosal melanomas (88%). Patients received toripalimab at 1 or 3 mg/kg via intravenous infusion every 2 weeks, in combination with axitinib 5 mg orally twice a day, in a dose-escalation and cohort-expansion study until confirmed disease progression, unacceptable toxicity, or voluntary withdrawal. The primary objective was safety. Secondary objectives included efficacy, pharmacokinetics, pharmacodynamics, immunogenicity, and tumor tissue biomarkers. RESULTS Thirty-three patients were enrolled. No dose-limiting toxicities were observed. Ninety-seven percent of patients experienced treatment-related adverse events (TRAEs). The most common TRAEs were mild (grade 1 or 2) and included diarrhea, proteinuria, hand and foot syndrome, fatigue, AST or ALT elevation, hypertension, hypo- or hyperthyroidism, and rash. Grade 3 or greater TRAEs occurred in 39.4% of patients. By the cutoff date, among 29 patients with chemotherapy-naïve mucosal melanoma, 14 patients (48.3%; 95% CI, 29.4% to 67.5%) achieved objective response, and the median progression-free survival time was 7.5 months (95% CI, 3.7 months to not reached) per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. CONCLUSION The combination of toripalimab plus axitinib was tolerable and showed promising antitumor activity in patients with treatment-naïve metastatic mucosal melanoma. Patients enrolled in this study were all Asian, and this combination therapy must be validated in a randomized phase III trial that includes a non-Asian population before it can become a standard of care.

Recent adjuvant vascular endothelial growth factor tyrosine kinase inhibitor trials in resected high-risk renal cell carcinoma that compared sunitinib, sorafenib, pazopanib, and axitinib with placebo controls have demonstrated mixed impact on disease-free survival, no improvement in overall survival, and, thus, controversy. Here, we discuss the results and conduct of these trials to provide new insight into the goals and strategies of treating resected renal cell cancer that is at high risk for recurrence. The potential for leveraging what we have learned from these trials to conduct successful contemporary adjuvant and perioperative immune checkpoint inhibition trials and future adjuvant trial design is discussed.

The treatment paradigm for advanced and metastatic renal cell carcinoma (mRCC) has evolved rapidly since the arrival of targeted therapies and novel immunotherapies. mRCC was previously treated only with cytokines. However, discoveries of mutations affecting the von Hippel–Lindau tumor suppressor gene (leading to increased expression of VEGF and hypoxia inducible factor/HIF-1) and of deregulations in the phosphatidylinositol-3 kinase/AKT/mTOR pathway (resulting in tumor angiogenesis, cell proliferation, and tumor growth) have led to the development of numerous targeted therapies. The U.S. Food and Drug Administration (FDA) has thus approved a total of nine targeted therapies since 2005, including VEGF tyrosine kinase inhibitors (sunitinib, pazopanib, axitinib, sorafenib, and lenvatinib), a monoclonal antibody targeting VEGF (bevacizumab), mTOR inhibitors (temsirolimus and everolimus), and a multityrosine kinase inhibitor (cabozantinib). Furthermore, the development of immune checkpoint inhibitors has again shifted the mRCC therapeutic landscape with the FDA’s approval of nivolumab. Herein, we discuss the unprecedented changes in the field of clear cell histology mRCC in both the first-line and salvage settings, and we also discuss future therapies and recommend a treatment paradigm on sequencing of these agents.

4551 Background: Front-line treatment for patients (pts) with metastatic clear cell renal cell carcinoma (mRCC) has undergone rapid advances in the last five years. This evolution has led to uncertainty about the optimal first line combination regimen. Herein, we compare real-world outcomes in pts treated with either axitinib/pembrolizumab (A/P) or ipilimumab/nivolumab (I/N) reported by International Metastatic RCC Database Consortium (IMDC) score. Methods: The nationwide Flatiron Health electronic health records-derived database was used to select pts diagnosed with mRCC and treated with front-line A/P or I/N from 2018-2020. The primary endpoints were overall-survival (OS) and real-world progression free survival (rwPFS). The survival analyses were adjusted using propensity score-based Inverse Probability of Treatment weighting, providing balance on age, gender, insurance, race, IMDC, practice type, and nephrectomy. Survival was assessed from beginning of therapy, and survival by treatment groups was compared using weighted and unweighted Kaplan-Meier curves with log-rank tests and weighted Cox proportional hazards regressions. Disease characteristics between the treatment groups were compared using chi-square and T-tests. Results: 821 pts received frontline A/P (n=259) or I/N (n= 562). Demographics and clinical parameters were similar between the two cohorts. Median age was 66 years, 73% were male, and 54.9% had a nephrectomy. 459 pts had all IMDC criteria factors available, 242 pts had missing factors but enough to define as intermediate/poor risk, 120 pts had unknown IMDC risk. Adjusted median OS was not statistically different: mOS for A/P was not reached (NR) while I/N was 22 mo (95% CI, 19.8-NR; p=0.40). Twelve-month survival was 68.5% for A/P treated pts and 65.8% for I/N treated pts (P=0.41). Twelve-month rwPFS was 41.4% for A/P treated pts and 39.7% for I/N treated pts (P=0.14). No statistical difference in survival was seen within IMDC risk strata (see table). Conclusions: In this retrospective, real-world study of pts treated with front-line A/P or I/N, 12-month survival was not statistically different irrespective of IMDC risk. Longer follow-up will be necessary to discern any significant differences.[Table: see text]

e16536 Background: Axitinib has been used extensively as a single agent or in combination with immunotherapy in the treatment of advanced renal cell carcinoma. It can be often discontinued due to adverse events. A meta-analysis of clinical trials was performed to evaluate the overall tolerability of axitinib in this setting. Methods: PubMed (Up to November 2020) was searched to identify clinical trials of axitinib in advanced or metastatic renal cell carcinoma. Reported data was collected to include axitinib and control discontinuation due to adverse events. A random or fixed effects model was used to determine summary incidences, relative risks, and 95% confidence intervals depending on the heterogeneity of included studies. Results: A total of 11 studies including 4,056 patients (axitinib alone n = 1384, axitinib combination n = 987, control n = 1685) were included for analysis. The summary discontinuation rate for axitinib due to adverse events was 13.4% (95% CI; 11.7-15.2%) with 8.9% (95% CI: 5.3-14.6%) as a single agent and 26.6% (95% CI:17.8 –37.8%) in combination with other agents. In comparison with controls based on randomized controlled studies, axitinib overall has similar discontinuation rate due to adverse events (RR: 1.18, 95% CI: 0.77-1.80). However, there was a significantly higher discontinuation rate with axitinib in combination with other agents including immunotherapeutic agents PD-L1 inhibitors than control treatment (RR: 1.52, 95% CI: 1.24-1.86). Conclusions: The tolerability of axitinib may vary significantly with its use as a single agent or in combination in the treatment of advanced renal cell carcinoma. Further studies are needed to improve its tolerability as a part of combination therapy.

4547 Background: In the phase 3 JAVELIN Renal 101 trial (NCT02684006), treatment-naive patients (pts) with aRCC demonstrated prolonged progression-free survival (PFS) and a higher objective response rate with A + Ax vs S. We report the association of blood-based biomarkers with differential responses to treatment. Methods: Biomarkers in pretreatment (pre-tx) and on-treatment (on-tx) blood samples from 886 enrolled pts were correlated with clinical outcomes and molecular profiling data from corresponding tumor samples. Analyses include blood counts of unique populations, T-cell receptor sequencing, circulating cytokines, and serum proteomics by mass spectrometry MALDI-TOF. Results: At baseline, higher pre-tx monocyte counts were associated with shorter PFS in the A + Ax arm (Table). In the S arm, higher pre-tx levels of multiple T-cell–related metrics, including the percent of productively rearranged peripheral T cells, were associated with longer PFS but had no association in the A + Ax arm (Table). Higher pre-tx neutrophil counts were associated with shorter PFS in both arms, but neutrophil-to-lymphocyte ratio (NLR) was only associated with PFS for the S arm (Table). On-therapy biomarkers showed differential post-tx changes in T-cell numbers and clones at C2D1. Tx-specific differences were also seen in non–T-cell populations such as monocytes and neutrophils at multiple time points through C3D1. Serum levels of pre- and on-tx VEGF, CRP, and several interleukins showed differential associations with PFS (eg, higher pre-tx VEGF was associated with shorter PFS in only the S arm) (Table). Specific genomic alterations in tumor tissues were associated with differences in several pre- and on-tx angiokines & cytokines. Conclusions: Response to treatment with first-line A + Ax or S was associated with immune fitness and tx-specific immunomodulation. We identified peripheral biomarkers in pts with aRCC associated with the presence of impactful genomic alterations and differential clinical outcomes. Clinical trial information: NCT02684006. [Table: see text]

4548 Background: CRP is an important prognostic and predictive factor in patients with aRCC receiving various therapies, such as cytokines and tyrosine kinase inhibitors. In this extended follow-up to the phase 3 JAVELIN Renal 101 trial (NCT02684006), we report the association of CRP levels at baseline (BL) and early after treatment with the efficacy of A + Ax or sunitinib (S). Methods: CRP levels were assessed at screening and day 1 of each 6-week cycle. Patients were categorized into CRP normal (BL CRP < 10 mg/L), normalized (BL CRP ≥10 mg/L and ≥1 CRP value decreased to < 10 mg/L during 6 weeks of treatment), and non-normalized (CRP ≥10 mg/L at BL and during 6 weeks of treatment) groups. Multivariate analysis of BL characteristics, including CRP for efficacy, was also conducted. Progression-free survival (PFS) and best overall response per independent central review (RECIST 1.1) from the second interim analysis (IA2) of overall survival (OS) and OS from the third interim analysis (IA3) were assessed. Results: Minimum duration of follow-up for IA2 and IA3 were 13 and 28 months, respectively. The table shows objective response rate (ORR), PFS, and OS by CRP group. Efficacy outcomes in the normal and normalized groups were favorable compared with the non-normalized group with both A + Ax and S. In the A + Ax arm, the complete response rate was 11.8% (normalized group), 3.8% (normal group), and 0.9% (non-normalized group). With A + Ax, the PFS in the normalized group was longer than in the normal group, but this was not observed with S. In each CRP group, all efficacy outcomes were favorable with A + Ax vs S. In the multivariate analysis, normalized or non-normalized CRP was an independent predictive factor of ORR or OS with A + Ax. Conclusions: Normal and normalized CRP levels were associated with improved A + Ax efficacy. A + Ax demonstrated favorable efficacy across CRP groups. OS in this study was immature; follow-up for the final analysis is ongoing. Further research in defining predictive value of CRP is warranted. Clinical trial information: NCT02684006. [Table: see text]

4500 Background: In the first interim analysis of the randomized, multicenter, open-label, phase 3 KEYNOTE-426 study (NCT02853331), treatment with pembro + axi significantly improved OS, PFS, and ORR vs sunitinib monotherapy in treatment-naive advanced ccRCC. Extended follow-up (median, 30.6 mo) continued to demonstrate the superior efficacy of pembro + axi vs sunitinib monotherapy in this patient population. Here, we present the results of the prespecified final analysis with 42.8-mo median follow-up. Methods: Treatment-naive patients (pts) with advanced ccRCC, KPS ≥70%, and measurable disease (RECIST v1.1) were randomly assigned 1:1 to receive pembro 200 mg IV Q3W for up to 35 doses + axi 5 mg orally BID or sunitinib 50 mg orally QD on a 4-wk on/2-wk off schedule until progression, intolerable toxicity, or withdrawal. Randomization was stratified by IMDC risk (favorable vs intermediate vs poor) and geographic region (North America vs Western Europe vs Rest of World). Dual primary endpoints were OS and PFS. Secondary endpoints were ORR, DOR, and safety. The protocol-specified final analysis was based on a target of 404 OS events. No formal hypothesis testing was performed because all efficacy endpoints were met previously at the first interim analysis; nominal P values are reported. Results: Overall, 861 pts were randomly assigned to receive pembro + axi (n=432) or sunitinib (n=429). Median duration of follow-up, defined as time from randomization to the database cutoff date, was 42.8 mo (range, 35.6-50.6). At data cutoff, 418 pts had died: 193 (44.7%) of 432 pts in the pembro + axi arm vs 225 (52.4%) of 429 pts in the sunitinib arm. Compared with sunitinib, pembro + axi improved OS (median: 45.7 vs 40.1 mo; HR, 0.73 [95% CI, 0.60-0.88]; P

4574 Background: In the phase 3 JAVELIN Renal 101 trial (NCT02684006), treatment-naive patients with aRCC receiving A + Ax showed improved progression-free survival (PFS) and objective response rate (ORR) across International Metastatic RCC Database Consortium (IMDC) risk groups (favorable [F], intermediate [I], and poor [P]) compared with patients receiving S. Here we report updated efficacy results for A + Ax vs S by IMDC risk groups from the third interim analysis. Methods: Patients were randomized 1:1 to receive either A (10 mg/kg intravenously every 2 weeks) plus Ax (5 mg orally twice daily) or S (50 mg orally once daily) for 4 weeks (6-week cycle). Patients were categorized per IMDC risk group into F, I, and P subgroups, and outcomes were assessed for F, I, P, and I + P. Overall survival (OS) and PFS, ORR, complete response (CR), and duration of response (DoR) per investigator assessment (RECIST v1.1) were assessed. Results: The study enrolled 886 patients with aRCC. At data cutoff (Apr 2020), median (95% CI) follow-up for OS in the A + Ax was NR (42.2-NE) vs 37.8 (31.4-NE) months with S. The Table shows OS, PFS, ORR, CR, and DOR by IMDC risk group. A + Ax generally showed improved efficacy compared with S across IMDC groups. Conclusions: Consistent with previously reported results from prior interim analyses, extended follow-up confirms the efficacy benefits of A + Ax vs S across IMDC risk groups in patients with aRCC. Patients continue to be followed up for the final OS analysis. Clinical trial information: NCT02684006. [Table: see text]

4578 Background: Nivolumab in combination with cabozantinib (N+C) has demonstrated significantly improved progression-free survival (PFS), objective response rate (ORR), and overall survival (OS), compared with sunitinib as a first-line (1L) treatment for aRCC in the phase 3 CheckMate (CM) 9ER trial. As there are no head-to-head trials comparing N+C with pembrolizumab in combination with axitinib (P+A), this study compared the efficacy of N+C with P+A as 1L treatment in aRCC. Methods: An MAIC was conducted using individual patient data on N+C (N = 323) from the CM 9ER trial (median follow-up: 23.5 months) and published data on P+A (N = 432) from the KEYNOTE (KN)-426 trialof P+A (median follow-up: 30.6 months). Individual patients within the CM 9ER trial population were reweighted to match the key patient characteristics published in KN-426 trial, including age, gender, previous nephrectomy, International Metastatic RCC Database Consortium risk score, and sites of metastasis. After weighting, hazards ratios (HR) of PFS, duration of response (DoR), and OS comparing N+C vs. P+A were estimated using weighted Cox proportional hazards models, and ORR was compared using a weighted Wald test. All comparisons were conducted using the corresponding sunitinib arms as an anchor. Results: After weighting, patient characteristics in the CM 9ER trial were comparable to those in the KN-426 trial. In the weighted population, N+C had a median PFS of 19.3 months (95% CI: 15.2, 22.4) compared to a median PFS of 15.7 months (95% CI: 13.7, 20.6) for P+A. Using sunitinib as an anchor arm, N+C was associated with a 30% reduction in risk of progression or death compared to P+A, (HR: 0.70, 95% CI: 0.53, 0.93; P = 0.015; table). In addition, N+C was associated with numerically, although not statistically, higher improvement in ORR vs sunitinib (difference: 8.4%, 95% CI: -1.7%, 18.4%; P = 0.105) and improved DoR (HR: 0.79; 95% CI: 0.47, 1.31; P = 0.359). Similar OS outcomes were observed for N+C and P+A (HR: 0.99; 95% CI: 0.67, 1.44; P = 0.940). Conclusions: After adjusting for cross-trial differences, N+C had a more favorable efficacy profile compared to P+A, including statistically significant PFS benefits, numerically improved ORR and DoR, and similar OS.[Table: see text]

TPS5609 Background: Despite significant strides in understanding the molecular pathogenesis of EC, there remain few effective therapies for recurrent disease. Deeper insight into the roles of disordered tumor vasculature and HIF1α- and VEGF-mediated immunosuppressive effects on myeloid-derived suppressor cells, T-cells, and PD-L1 expression contributed to the development of new targeted regimens. Activity of pembrolizumab and lenvatinib was demonstrated in a phase 2 trial in MMR-P EC (NCT02501096). By inhibiting VEGF receptor (VEGFR) and PD-L1 signaling, immunologically “cold” tumors may become inflamed. However, there are concerns regarding the toxicity of pembrolizumab/lenvatinib and alternatives are sought. The combination of the anti-PD-L1 antibody avelumab with axitinib, an inhibitor of VEGFR 1-3 and PDGFR with more potent IC50 inhibitory activity than lenvatinib, has also shown synergistic activity and is FDA approved as first line treatment for patients with renal cell cancer. We therefore hypothesized that this combination would be well tolerated and efficacious in recurrent MMR-P EC. Methods: This is an investigator-initiated, phase 2, two-stage single cohort trial evaluating avelumab with axitinib in recurrent or persistent EC. Participants must have MMR-P EC of any histology and have received at least one chemotherapeutic regimen, with no upper limit on the number of prior lines received. Prior use of immune checkpoint (IC) inhibitors is excluded. Treatment consists of avelumab 800mg IV every 2 weeks and axitinib 5mg orally twice daily. Co-primary endpoints are progression-free survival at 6 months (PFS6) and objective response rate by RECIST 1.1. Translational objectives include characterization of tumor-infiltrating lymphocytes, infiltrating myeloid cells, expression of IC markers, and whole exome sequencing to evaluate mutations in genes related to DNA repair and immunologic response. This is a two-stage design in the method of Sill et al, with 16 participants anticipated in stage 1 and 19 participants in stage 2, for a total of 35 participants. Accrual is ongoing. Clinical trial information: NCT02912572.

4514 Background: There are limited data on the outcomes of patients receiving second-line (2L) therapy following immunotherapies plus tyrosine-kinase inhibitors in the first-line (1L). We describe the outcomes of patients with advanced renal cell carcinoma (aRCC) who had received 1L A + Ax in the phase 3 JAVELIN Renal 101 trial and went on to receive subsequent Tx. Methods: At the cutoff date for the third interim analysis (April 28, 2020), patients who received 1L A + Ax (n = 442) and received any subsequent lines of Tx were assessed. We report the overall survival (OS), progression-free survival on next-line systemic therapy (PFS2) per type of Tx, and duration of 2L Tx. Results: Anticancer drug therapies were received by 204/442 patients following A + Ax Tx. Of patients who received a follow-up anticancer drug Tx, 163/204 received a single agent (SA), and 41/204 received a combination Tx (CT) regimen. The most common 2L SA was cabozantinib (60/163), and the most frequent 2L CT was everolimus + lenvatinib (12/41). OS, PFS2, and duration of treatment (DOT) for the various subgroups are summarized in the table below. Analyses on additional subgroups will also be presented. Conclusions: In patients with aRCC who received 2L CT following 1L treatment with A + Ax, long-term OS and PFS2 were observed. Clinical trial information: NCT02684006. [Table: see text]

9512 Background: The outcome of patients (pts) with resectable mucosal melanoma (MM) is still poor. Toripalimab combined with axitinib has shown impressive results in metastatic MM with an ORR of 48.3% and a median PFS of 7.5 months in a phase 1b trial. It was hypothesized that this combination therapy might cause pathologic response in neoadjuvant setting for resectable MM, so we conducted this single arm phase 2 trial. Methods: Eligible pts were adults (aged 18 to 75) with histologically confirmed resectable (localized or regional lymph node metastasis) MM disease. Exclusion criteria included ocular or unknown primary melanoma, distant metastatic disease or previous use of anti PD-1 ab. Pts received toripalimab 3 mg/kg Q2W plus axitinib 5 mg BID for 8 weeks as neoadjuvant therapy, then surgery and the adjuvant toripalimab 3 mg/kg Q2W starting 2±1week after surgery for totally 52 weeks. The primary end point is pathologic response rate according to the International Neoadjuvant Melanoma Consortium (pCR+pPR, pCR is defined as the complete absence of residual viable tumor and pPR ≤ 50% of viable tumor cells). The secondary end point is RFS in the ITT population. Clinical trial information: NCT04180995. Results: From Aug 2019 to Dec 2020, 21 pts have been eligible and enrolled. Basic characteristics: median age 62 years; M: F 28.6% : 71.4%; primary sites 8 femal genital(1urethra, 7vagina), 5 esophagus, 4 ano-rectal, 4 head & neck(3 nasal,1 oral), in which 47.6% localized disease (T3/4 60%), 52.4% regional lymphatic disease; Gene mutation: 4 cKit (1 amplification), 2 Nras,1 Braf (N581), 1mTOR. This therapy was tolerable with grade 3-4 treatment related AEs of 23.8% (liver dysfunction 14.3%, hyperglycemia 9.5% and hypertension 4.8%). 13 pts had received surgeries (local excision 30.8%, wide excision ± CLND72.7%)and 5 pts still in neoadjuvant treatment. One patient was inoperable for bone metastasis, and 2 pts withdrew for covid 19 epidemic. At a median follow up time of 59 weeks, the pathologic response rate was 28.6% (4/14, 2 pCR, 2pPR). Of the post-surgical specimens, 61.5% (8/13) showed significant TIL infiltration, with 38.5% Brisk and 23.1% Nonbrisk according to the definition of AJCC 8th edition. Plenty of plasma cells, histiocyte and pigment with hyaline fibrosis were also found in responders. No recurrence or metastasis was observed in responders until now, with a RFS reaching more than 58weeks. 5 pts with pNR( > 50% viable tumor cells) got disease progression, with 1 local recurrence, 1 regional lymphatic metastasis, and 3 distant metastases. The median RFS has not been reached. Conclusions: Neoadjuvant toripalimab plus axitinib in resectable MM has shown promising pathologic responses with good tolerance, which supports further investigation of neoadjuvant therapies in MM. Survival is still in follow-up. Clinical trial information: NCT04180995.

4573 Background: Antibodies targeting PD-1/PD-L1 combined with vascular endothelial growth factor (VEGF) inhibitors are a front-line standard of care for metastatic RCC. Neoadjuvant use of these combinations is associated with tumor downsizing, but dynamic effects on key immune biomarkers are uncertain. We report early dynamic changes in the tumour immune environment after neoadjuvant treatment with avelumab/axitinib. Methods: Neoavax is an open label, single arm, phase II trial, investigating 12 weeks of neoadjuvant avelumab/axitinib prior to nephrectomy in patients with high-risk non-metastatic clear-cell (cc) RCC (cT1b-4N0-1M0). Partial primary tumour response (RECIST 1.1) occurring in ≥25% is the primary endpoint. Biomarker analysis on sequential tissue is an exploratory endpoint. Expression of PD-L1 (SP263), CD8+, CD8-granzyme-B (CD8/GZMB)+, Foxp3+ cells, CD8/CD39+ and major histocompatibility complex class I (MHC-I) were compared on paired samples (pre-treatment biopsy and nephrectomy) (NCT03341845). Results: Paired, sequential tissue from the first 24 patients was analysed for immune biomarker expression. Of these patients, 70% were ≥pT3a, 30% pN1, 58% had ISUP/WHO grade ≥3 with 8% sarcomatoid features. Compared to pre-treatment biopsy there was a significant increase in PD-L1 (p = 0.0002) and CD8+ expression (p = 0.0003) after therapy, whereas changes in CD8/GZMB+, MHC-I and CD8/CD39+ were not significant. Furthermore, neoadjuvant avelumab/axitinib therapy was associated with a significant decrease in Foxp3+ cells (p = 0.009). Conclusions: 12 weeks of neoadjuvant axitinib/avelumab treatment in ccRCC leads to significant dynamic changes in the tumour microenvironment for CD8+, PD-L1 and Foxp3+ expression. High baseline Foxp3+ infiltration is associated with an unfavorable outcome in the majority of solid tumours. The significant on-treatment decrease in Foxp3+ may account for the positive interaction seen between VEGF targeted therapy and immune checkpoint inhibitors in mRCC. If these cells represent regulatory T cells (Tregs), activated CD4 T cells or fragile Tregs remains to be determined. Clinical trial information: NCT03341845.

302 Background: In the phase III JAVELIN Renal 101 trial (NCT02684006), A + Ax demonstrated progression-free survival (PFS) and objective response rate (ORR) benefit across IMDC risk groups (favorable, intermediate, and poor) vs S in patients with previously untreated aRCC. Here we report efficacy of A + Ax vs S by number of IMDC risk factors (0, 1, 2, 3, and 4-6) and target tumor sites (1, 2, 3, and ≥4) at baseline from the second interim analysis of overall survival (OS). Methods: Patients were randomized 1:1 to receive A 10 mg/kg intravenously every 2 wk + Ax 5 mg orally twice daily or S 50 mg orally once daily for 4 wk (6-wk cycle). PFS and ORR per independent central review (RECIST 1.1) and OS were assessed. Results: At data cut-off (Jan 2019), median (m) follow-up for OS and PFS was 19.3 vs 19.2 mo and 16.8 vs 15.2 mo for the A + Ax vs S arm, respectively. The table shows OS, PFS, and ORR by number of IMDC risk factors and target tumor sites at baseline. A + Ax generally demonstrated efficacy benefit vs S across subgroups. Conclusions: With extended follow-up, A + Ax generally demonstrated efficacy benefit vs S across the number of IMDC risk factors and tumor sites at baseline in aRCC. OS was still immature; follow-up for the final analysis is ongoing. Clinical trial information: NCT02684006 . [Table: see text]

294 Background: The combination of the immune checkpoint inhibitor avelumab and VEGF-targeted, antiangiogenic tyrosine kinase inhibitor axitinib (AA) has demonstrated superior PFS and ORR compared to sunitinib in patients with mRCC and is an option for first line treatment across all IMDC risk scores. In this retrospective review we report our real world experience of this combination in three cancer centres in the Northwest of England. Methods: Treatment naïve mRCC patients receiving AA through the Early Access to Medicine Scheme at 3 cancer sites in the UK between May 2019 and July 2020 were identified. Primary outcomes of interest include overall response rate (ORR), adverse events (AEs) and preliminary survival observations. Results: A total of 44 patients were identified with a median follow up of 6.9 months (0.8-13.5 mo). Median age was 68 (48-81); 68% were male. The patients’ adult comorbidity evaluation score (ACE-27) was calculated: 0 = 43%, 1 = 30%, 2 = 7% and 3 = 20% . 45%, 48% and 7% of patients had favourable (F), intermediate (I) and poor (P) IMDC risk scores respectively. All had clear cell histology with 16% demonstrating sarcomatoid change. Most patients had undergone a nephrectomy (70%) and 36% had a single organ site of metastatic disease. ORR in the whole cohort was 60% (CR 5%, PR 55%, SD 25%, PD 2%, NE 13 %). Median time to first response was 2.6 months (0.6- 8.2mo). At time of data cut-off, 64% of patients remain on treatment (80% F, 48% I and 67% P). 14% of patients discontinued treatment due to disease progression while 22% stopped due to toxicity. The majority of patients (68%) continued axitinib at the starting dose of 5mg BD. Dose escalation of axitinib was possible in 9% patients while 23% needed a dose reduction due to toxicities. AEs were observed in 36 (82%) patients (G3 36%); the commonest being mucositis 30%; hypertension 23% (G3 11%); fatigue 25%; thyroid dysfunction 18%; diarrhoea 20% (G3 5%); hepatitis 20% (G3 11%). 9% of patients experienced an infusion reaction to avelumab. Overall, 9 (20%) patients received steroids for suspected immune related adverse events (irAEs); 6 (14%) were managed as G3≤ irAEs. 9 (20%) patients required inpatient admission due to AEs; 5 (11%) were associated with irAEs. Of the patients who discontinued AA treatment, 50% received subsequent therapy (12.5%, 75% and 12.5% receiving combination checkpoint inhibitor therapy, other VEFG TKi and TKi/MTOR combination respectively). 4 patients remain on active surveillance with no evidence of progression. Conclusions: Our early experience of AA in this real world setting reports comparable clinical responses to the published data. Treatment is well tolerated, with lower than expected levels of G3 or above AEs which is reassuring in a non-trial selected population. Follow-up is ongoing and updated efficacy and safety outcomes will be presented.

301 Background: In the phase III JAVELIN Renal 101 trial (NCT02684006), A + Ax demonstrated significantly longer progression-free survival (PFS) and a higher objective response rate (ORR) vs S in patients with previously untreated aRCC. The role of immune checkpoint + VEGFR inhibition in elderly patients remains unclear. Here we report the efficacy of A + Ax vs S by age group from the second interim analysis (IA) of overall survival (OS) and the safety of A + Ax by age group from the first IA. Methods: Patients were randomized 1:1 to receive A 10 mg/kg intravenously every 2 wk + Ax 5 mg orally twice daily or S 50 mg orally once daily for 4 wk (6-wk cycle). PFS and ORR per independent central review (RECIST 1.1), OS, and safety by age group (

322 Background: Hypoxia induced factor 1α/2α (HIFs) and vascular endothelial growth factor (VEGF) are overexpressed in ccRCC and associated with increased tumor angiogenesis, vascular instability and drug resistance. In xenografts, high dose SLM resulted in sustained down regulation of HIFs, normalization of tumor vasculature that resulted in increased drug delivery, and therapeutic synergy with anti-VEGF therapeutic. These effects were highly SLM dose, sequence, and schedule dependent. Methods: After completion of the escalating phase I (3+3) trial, the non-toxic SLM dose of 4000μg was administered orally twice daily (BID) for 14 days, followed by once daily in combination with axitinib 5 mg BID. The primary endpoint is safety and the secondary end point include overall response rate (ORR), progression free survival (PFS), and overall survival (OS). To assess the potential effects of SLM on tumor vascular function, dual energy computed tomography (DECT) was conducted at baseline, day 14 of SLM, and at 3 months of SLM + axitinib. Results: Thirty subjects are screened. Of whom 25 have efficacy data (3 subjects screen failure, 1 withdrew, 1 taken off study prior to first scan due to progression with brain lesions likely present prior to study entry). 13/25 (52%) have confirmed response (CR/PR). Two subjects had CR lasting for at least 35 and 44 months, 6 subjects achieved stable disease (SD) lasting at least 6 months accounting for disease control rate (DCR) of 76%, mPFS is 9.5 months. 5/30 patients have sarcomatoid features, all of which are evaluable for efficacy with 1 PR achieved (20%). In the 20 patients without sarcomatoid features, 12/20 achieved PR (60%). The most prevalent adverse events (AE) included fatigue, diarrhea, anorexia, nausea, hoarseness, weight loss, and hypertension. No deaths nor grade 4 toxicities observed. The blood selenium concentrations achieved in the 4000μg SLM dose cohorts are similar to those determined molecularly and therapeutically synergistic with axitinib in xenografts and are being achieved clinically without significant toxicity. DECT data demonstrated increased iodine uptake by tumor lesions, but not in normal tissues, on day 14 SLM treatment and decreased in these same lesions at 3 months of SLM/axitinib. Conclusions: Blood selenium concentrations and duration of treatment seem to be critical determinants of response. Pre and concurrent treatment with SLM enhance the ORR and PFS of axitinib, with no additional toxicity. Currently documented responses are similar across IMDC risk groups. Clinical trial information: NCT02535533 .

278 Background: Tivozanib (T) is a potent and highly selective VEGF receptor (R) tyrosine kinase inhibitor in clinical development for RCC. Axitinib is also a potent and selective VEGF-R inhibitor now commonly part of front-line aRCC treatment. The activity of T after axitinib has not been previously defined. The activity of T after prior therapy types including axitinib is of clinical relevance. Methods: The pivotal TIVO-3 study enrolled subjects with mRCC who failed 2 or 3 prior systemic regimens, one of which included a VEGFR TKI, stratified by IMDC risk category and type of prior therapy (two TKIs; TKI plus checkpoint; TKI + other) then randomized in a 1:1 ratio to T or S. The primary objective of the overall trial was to compare progression free survival (PFS) by blinded independent radiological review. Patients with prior axitinib received as monotherapy in the second or third line setting and other predefined subgroups were reviewed for outcome with T. Results: Patients treated with T after prior axitinib had a PFS of 5.5 months and an ORR of 13% compared to 3.7 months and 8% for patients treated with S. Other subgroups are presented in the table below. Clinical trial information: NCT02627963 . Conclusions: Tivozanib improved PFS vs. sorafenib in patients who have progressed after multiple VEGFR-TKIs, including patients with prior second or third line axitinib treatment. These results suggest differential activity from tivozanib and axitinib despite both being potent and selective VEGF-R inhibitors. [Table: see text]

275 Background: Venous tumor thrombus (VTT) extension occurs in 4-15% cases of renal cell cancer (RCC). The Mayo classification distinguishes 4 levels of VTT extension between the renal vein and supradiaphragmatic inferior vena cava (IVC). Although surgery is performed with curative intent, mortality is high (5-15%) with complications increasing with the level of the VTT. 5-year survival rates are poor; ~40-65% in non-metastatic RCC. It is hypothesised that neoadjuvant targeted therapy could downstage the VTT reducing the extent of surgery, leading to reduced surgical morbidity and mortality, and increased survival. However, level I or II evidence is lacking. NAXIVA provides the first level II evidence in this patient group, assessing the response of VTT to axitinib. Extensive translational sampling will provide in depth interrogation of VTT (using genomics, proteomics, immunophenotyping and metabolomics) to examine the role of the tumor microenvironment of VTT and response to axitinib. Methods: NAXIVA was a single arm, single agent, multi-center phase 2 feasibility study of axitinib in patients with both metastatic and non-metastatic clear cell RCC prior to nephrectomy and thrombectomy. A Simon two stage minimax design was adopted and the trial designed for adequate power to distinguish a 25% improvement in the Mayo VTT level. 21 patients were recruited over a 24 month period between 15/Dec/2017 and 06/Jan/2020 at 5 sites across the UK. Patients were treated with 8 weeks of axitinib (starting dose 5mg bd, increasing to 10mg bd as tolerated) prior to planned surgery. The primary endpoint was the percentage of evaluable patients with an improvement in VTT according to the Mayo classification (assessed using MRI abdomen scans at screening and week 9, prior to surgery. Secondary endpoints were percentage change in surgical approach, percentage change in VTT height, response rate (by RECIST) and evaluation of surgical morbidity assessed by Clavien-Dindo classification. Results: The percentage of evaluable patients with an improvement in VTT according to the Mayo classification was 26.58% [80% CI: 15.76%, 39.74%] (6 of 21 evaluable patients). 35.29% (6 of 17 patients who progressed to surgery) had a change in surgical approach to a less invasive option. There was a median percentage reduction in VTT height of 21.49% (SD=27.60%). The response rate (by RECIST) in the evaluable population was 61.90% SD, 14.29% PR, 9.52% PD. In terms of surgical morbidity 11.76% (2 of 17 patients who progressed to surgery) experienced a Clavien-Dindo 3 or greater complication (0 CD3, 1 CD4, 1 CD5). Conclusions: NAXIVA provides unique prospective data on the feasibility of neoadjuvant axitinib administration to down stage IVC VTT and reduce the extent of surgery. Work is ongoing to establish predictors of response. Clinical trial information: NCT03494816 .

327 Background: In the randomized, open-label, phase III KEYNOTE-426 study (NCT02853331), pembrolizumab + axitinib significantly improved overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) versus sunitinib as first-line therapy for advanced RCC. Per protocol, patients could discontinue pembrolizumab or axitinib and continue the other agent. Pembrolizumab was stopped for all patients at 2 years. Axitinib could be continued until progression or toxicity. This exploratory subgroup analysis of KEYNOTE-426 describes outcomes of patients who completed 2 years of pembrolizumab. Methods: Patients included in KEYNOTE-426 were treatment naive, with clear cell RCC, KPS ≥70%, and measurable disease (RECIST v1.1). Patients were randomly assigned 1:1 to receive pembrolizumab 200 mg intravenously every 3 weeks for up to 35 doses + axitinib 5 mg orally twice daily or sunitinib 50 mg once daily (4 weeks on/2 weeks off) until progression, toxicity, or withdrawal. Primary end points of the original analysis were OS and PFS. Key secondary end points were ORR and safety. Results: Of 432 patients treated with pembrolizumab + axitinib, 129 (29.9%) completed 2 years of study therapy. Median (range) age of these patients was 61 (36-82) years, and 72.1% were male; 42 (32.6%) and 87 (67.4%) patients had International mRCC Database Consortium favorable and intermediate/poor risk, respectively, consistent with the intention-to-treat population (31.9% vs 68.1%). Median (range) follow-up (time from randomization to data cutoff) was 31.1 (24.0-37.7) months. For patients who completed 2 years of study therapy, the OS rates at 36 months was 93.8% (95% CI, 85.5%-97.4%). The PFS rates at 24 and 36 months were 72.7% (95% CI, 64.0%-79.7%) and 57.7% (95% CI, 46.3%-67.5%), respectively. The ORR was 85.3%, and the CR rate was 14.0%. 59.7% of patients experienced grade 3-5 treatment-related adverse events and 8.5% experienced grade 3-5 immune-mediated adverse events. Conclusions: In this exploratory analysis, a significant proportion of patients in the pembrolizumab + axitinib arm completed 2 years of pembrolizumab with ongoing clinical benefit. Clinical trial information: NCT02853331 .

360 Background: Angiogenesis plays an important role in NET development and progression. Axitinib is a potent and selective VEGFR-1,2,3 inhibitor, with proven activity against several vascular-dependent solid tumors. The aim of this randomized, double-blind phase II/III study was to assess the efficacy of axitinib in patients with advanced G1-2 extra-pancreatic NETs. Methods: Eligible pts were randomized (1:1) to receive octreotide LAR (30 mg IM q4w) with axitinib (5 mg BID) or placebo BID until disease progression or unacceptable toxicity. Pteswere stratified by time from diagnosis to study entry ( > or < 12m), primary tumor site (GI tract vs non-GI) and Ki-67 index (< 5% vs > 5%). Prior therapy with SSA, IFN and up to 2 lines of systemic treatment was allowed, but not prior VEGF- or VEGFR-targeted drugs. Clinical and/or radiological disease progression within 12 months prior to study entry was required. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), time to progression, overall response rate (ORR), duration of response, biochemical response and safety. Results: 256 pts were randomized (106 in the Phase II part, and 150 additional pts in the Phase III part), 126 to axitinib and 130 to placebo. The main characteristics of the study population were: median age 61 years (range: 21-85), 52% male, PS 0-1 (64-35%), G1-2 (29%-71%), primary tumor site GI (40%)-Lung (17%)-Other (32%). Prior therapies included: SSA (46%), everolimus (13%), chemotherapy (13%), TACE (5%) and PRRT (2%). ORR was significantly higher in axitinib- vs placebo-treated patients (17.5% vs 3.8%, p = 0.0004). PFS per investigator assessment also favored axitinib vs placebo-treated patients, although the difference did not reach statistical significance (median PFS 17.2 vs 12.3 months, respectively, HR 0.816, p = 0.169). Grade 3-4 treatment-related AEs occurred more frequently in the axitinib vs placebo arm (52% vs 13.8%), and included hypertension (21% vs 6 %), cardiac disorders (3.2% vs 0.7%), diarrhoea (13% vs 1.5 %), asthenia (9% vs 3%) and nausea&vomiting (2% vs 0.7%). There were 3 treatment-related deaths, 1 in the axitinib arm (cardiac failure) and 2 in the placebo arm (myocardial infarction and hepatorenal syndrome). Conclusions: Although the study failed to demonstrate a significant PFS benefit per investigator assessment, axitinib in combination with octreotide LAR demonstrated activity and had a tolerable safety profile in patients with advanced G1-2 extra-pancreatic NETs. Data base cleaning and central blinded radiological PFS assessment are currently ongoing. Clinical trial information: NCT01744249.

e21114 Background: Patients (pts) with advanced B3 thymoma (B3T) and thymic carcinoma (TC) resistant to chemotherapy have limited treatment options. Treatment with Anti-PD1 showed not negligible toxicity and limited activity, and anti-VEGFR drugs obtained limited and short lasting antitumor responses. No data on combined anti-PD1/PD-L1 with antiangiogenic drugs are available in B3T/TC. We report preliminary results on safety and activity of avelumab combined with axitinib in this pts population. Methods: The CAVEATT is a single arm, multicentric, phase II trial in immunotherapy-naive pts with advanced B3T or TC, progressing after at least one line of platinum based chemotherapy. Prior therapy with antiangiogenic drugs is allowed. Pts received Avelumab 10 mg/kg iv every 2 weeks and Axitinib 5 mg twice a day until progression or toxicity. The primary objective of the study is overall response rate (ORR) by RECIST 1.1; secondary endpoints include ORR by irRC and ITMIG, and QoL by EORTC QLQ-C30. An interim futility analysis is planned after the enrollment of the first 18 patients. If at least 5 out of 18 patients will obtain a PR, the accrual will continue to reach the total number of 33 pts, according with a Simon’s minimax design. Tumor and blood samples are collected at baseline and whenever feasible at disease progression, to identify predictive biomarkers of response and mechanisms of resistance to treatment. Results: 1 pt with B3T and 12 with TC were enrolled from April 2019 to January 2020. Median age was 59 years (range 33-77). 8 pts received ≥2 previous line of therapies, and 6 pts were pretreated with an antiangiogenic drug. The median follow-up was 5.1 months. 10 pts were evaluable for response. The proportions of patients who achieved a partial response (PR) or a stable disease (SD) were respectively 40% (95% CI 17%–69%) and 60% (95% CI 30%–83%). The median PFS was 7.9 months (95% CI 2.5–NA) 12 pts were evaluable for toxicity. Treatment-related adverse events (AE) of grade 1 or 2 occurred in 7 (58%) pts, and the most common was diarrhea (3 pts). Grade ≥3 AEs occurred in 2 (17%) pts: 1 had G3 hyperthension and 1 G3 hand foot syndrome, both leading to axitinib drug reduction. No immune-related AEs (irAEs) were observed. No patient stopped treatment for toxicity, 5 pts stopped for progressive disease, and 8 pts are still on treatment. Conclusions: Preliminary results suggest promising antitumor activity and a good toxicity profile of the combination of axitinib and avelumab in pts with advanced B3T and TC. Accrual is ongoing to reach the target of 33 pts Clinical trial information: 2017-004048-38 .

10007 Background: Metastatic mucosal melanoma responds poorly to PD-1 blockade therapy in comparison with cutaneous melanoma. Vascular endothelial growth factor (VEGF) is indicated to play an important immunosuppressive role in mucosal melanoma. Combination of VEGF inhibition with PD-1 blockade might provide therapeutic opportunities. Toripalimab was approved as a second-line treatment for metastasis melanoma in Dec 2018. This study is to evaluate the safety and clinical efficacy of toripalimab combined with axitinib for the treatment of metastatic mucosal melanoma. (Clinical trial ID: NCT03086174). Methods: Patients with metastatic melanoma receive 1 or 3 mg/kg toripalimab Q2W in combination with 5 mg axitinib BID until disease progression, unacceptable toxicity, or voluntary withdrawal. Clinical response is assessed every 8 weeks according to RECISTv1.1. Tumor PD-L1 expression, tumor mutational burden (TMB), and gene expression profile (GEP) will be evaluated for correlation with clinical response. Results: From April 2017 to April 2018, 33 patients were enrolled in the study. No DLT or treatment related death was observed. 97% patients experienced treatment related AE (TRAE) and 39.4% patients experienced Grade 3-4 TRAEs. Most common TRAEs include diarrhea, proteinuria, hand and foot syndrome and hypothyroidism. Only one patient discontinued treatment due to TRAE. Among 29 treatment naïve mucosal melanoma patients, 14 PR and 11 SD were observed for an ORR of 48.3% and a DCR of 86.2%. The median DOR was 13.7 months. The median PFS was 7.5 months and the median OS was 20.7 months. PD-L1 expression or TMB had no significant differences in responders versus non-responders. In contrast, GEP scores of eight selected immune-related and four angiogenesis-related genes showed strong correlation with clinical response, whereas previous published immune related signature or angiogenesis signature alone had no correlation. Conclusions: Toripalimab combined with axitinib is a promising treatment option for metastatic mucosal melanoma. GEP scores of selected immune-related and angiogenesis-related genes might predict the response to the combination. A randomized 3-arm Phase 2 trial has been initiated to compare toripalimab plus axitinib with toripalimab or axitinib alone. Clinical trial information: NCT03086174.

5008 Background: LEN, a multikinase VEGFR inhibitor, plus everolimus is approved for advanced RCC after prior VEGF-targeted therapy. PEMBRO, an anti-PD-1 antibody, plus axitinib is approved as first-line therapy of advanced RCC. We report phase 2 results of the RCC cohort of a phase 1b/2 trial (Study 111/KEYNOTE-146) of LEN + PEMBRO in patients (pts) who progressed after ICI therapy. Methods: We performed a multicenter, open-label study of pts with mccRCC, who previously had disease progression by RECIST (confirmed ≥ 4 weeks later) during or following ICI therapy. Pts had measurable disease by immune-related RECIST, and ≥ 1 prior therapy. Pts received LEN 20 mg orally once daily plus PEMBRO 200 mg IV every 3 weeks until disease progression or toxicity. Tumor assessments were performed every 6 weeks (until week 24), then every 9 weeks. The primary endpoint was objective response rate (ORR) at Week 24 by irRECIST. Results: 104 pts were enrolled. At data cutoff (January 12, 2020), 71 (69%) pts were still on study treatment. Most pts had ≥2 prior anticancer regimens (58%). 91 of 104 pts were evaluable for response at Week 12 (13 pts NE at Week 12); 46 of 91 pts achieved a confirmed partial response for an ORR of 51% (Table). Median progression-free survival (PFS) was 11.7 months and median duration of response (DOR) was 9.9 months. The most common treatment-related adverse events (TRAEs) were fatigue (49%), diarrhea (44%), proteinuria (37%), hypertension (31%), nausea (31%), dysphonia (29%), stomatitis (29%), and arthralgia (27%). There was 1 grade 5 TRAE (upper gastrointestinal hemorrhage). 43% of pts required dose reduction and 12% of pts discontinued treatment due to TRAEs. Response and safety data will be updated to include all pts evaluable at an April 9, 2020 cut-off. Conclusions: LEN + PEMBRO demonstrated promising antitumor activity in pts with mccRCC with disease progression following ICI therapy. No new safety signals were detected. Efficacy outcomes by investigator review per irRECIST. Clinical trial information: NCT02501096 . [Table: see text]

5080 Background: Axitinib (AXI) plus pembrolizumab (pembro) showed superior overall survival (OS), progression-free survival (PFS) and response rate compared with sunitinib in a randomized Phase 3 trial in advanced renal cell carcinoma (RCC). Here, we report long-term efficacy and safety data of the combination AXI/pembro from the Phase 1 trial, with almost 5 years of follow-up. Methods: 52 treatment-naïve patients with advanced RCC were enrolled between 23 September 2014 and 13 October 2015, and were treated with oral AXI 5 mg twice daily and intravenous pembro 2 mg/kg every 3 weeks. Planned treatment duration was 2 years for pembro and not limited for AXI. Based on International Metastatic Database Consortium (IMDC) criteria, 46.2%, 44.2% and 5.8% of patients were reported as having favourable, intermediate and poor risk. Results: At data cut-off date (July 3, 2019), median OS was not reached; 38 (73.1%) patients were alive. 14 (26.9%) patients had died, none were related to treatment. The probability of being alive was 96.1% (95% CI 85.2–99.0) at 1 year, 88.2% (95% CI 75.7– 94.5) at 2 years, 82.2 % (95% CI 68.5– 90.3) at 3 years, and 66.8 % (95% CI 49.1–79.5) at 4 years. Median PFS was 23.5 (95% CI 15.4–30.4) months. Median duration of response was 22.1 (95% CI 15.1–not evaluable) months. Median time on treatment with the combination AXI/pembro was 14.5 months (n=52), median time on pembro after AXI discontinuation was 9.0 months (n=10), and median time on AXI after pembro discontinuation was 7.5 months (n=11). After stopping study treatment, 22 patients received subsequent systemic therapy, including nivolumab and cabozantinib (n=6 each). Grade 3/4 AEs were reported in 38 (73.1%) patients. 20 (38.5%) patients discontinued either drug due to AEs: 17 (32.7%) patients discontinued AXI, and 13 (25.0%) patients discontinued pembro with 10 (19.2%) discontinuing both drugs. Dose reduction of AXI due to AEs was reported in 16 (30.8%) patients. The most common AEs reported were diarrhea (84.6%), fatigue (80.8%), hypertension (53.8%), cough (48.1%), and dysphonia (48.1%). Increased alanine aminotransferase and aspartate aminotransferase occurred in 44.2% and 36.5% of patients, respectively. With this longer follow-up, there were no cumulative AEs or new AEs. OS by IMDC risk group will be presented. Conclusions: In patients with advanced RCC with almost 5 years of follow-up, the combination of AXI/pembro continues to demonstrate clinical benefit with no new safety signals. Clinical trial information: NCT02133742 .

e22062 Background: This open-label, phase II study investigated the clinical activity and safety profile of axitinib, a potent and selective second-generation inhibitor of vascular endothelial growth factor receptors (VEGFR) in patients with stage III melanoma. Methods: Eligible patients had histology proven stage III melanoma, at least 1 target lesion as defined by RECIST, and no prior systemic therapy. Primary end point was objective response rate (ORR) according to RECIST v1.1; response was also considered if there was a ≥ 25% reduction in the involved nodal basin specific uptake value (SUV) on PET/CT. Secondary endpoints included duration of response (DOR), progression free survival (PFS), and overall survival (OS). Axitinib 5mg was given orally twice each day; treatment continued until tumor progression, unmanageable toxicity, or if the patient withdrew consent. After two months of therapy, patients then underwent definitive surgical resection of their involved nodal basins; one month after surgery patients would restart axitinib. In the 1st stage, 18 patients were to be enrolled; if there was ≥ 1 response, then the study would proceed to the 2nd stage with enrollment of additional 14 patients. At the end of the study, if there were at least 4 confirmed responses, then axitinib would be recommended for further studies in this patient population. Results: Fifteen patients were screened, and eleven patients were initiated on protocol therapy. Median age was 63 years (range 37-88). Three patients (27%) had BRAF mutations. Objective response rate was 45.5% [95% confidence interval (CI), 16.7-76.6], comprised of one complete and four partial responses, with two patients ongoing. Median duration of response was 8 months (95% CI, 3.5-13.3). Stable disease was observed in one patient, with an overall disease control rate of 54.5% (95% CI, 23.3-83.2]. Median progression free survival was 4 months [95% CI, 2.8-8.5]. Median overall survival was 59 months [95% CI, 29.6-67.5]. The most frequently reported ( > 15%) nonhematologic, treatment-related adverse effects were hypertension, fatigue, and diarrhea. Conclusions: Axitinib showed single-agent activity among patients with stage III melanoma and had favorable effect as a neoadjuvant therapy. Axitinib was well tolerated and safety profiles were consistent with previous reports from previous studies in patients with melanoma. Axitinib alone or combined with other therapies merits further research. Clinical trial information: NCT01321437.

9581 Background: The Worldwide Innovative Network (WIN) Consortium has developed the Simplified Interventional Mapping System (SIMS) algorithm in order to predict treatment response by comparing tumor and normal tissue biopsies on both genomic and transcriptomic platforms. SPRING is the first trial to assess a SIMS-based tri-therapy regimen in advanced non-small cell lung cancer (NSCLC). Methods: Patients with advanced NSCLC (no EGFR or ALK alterations; no ROS1 alterations if tested; PD-L1 unrestricted; ≤2 prior therapy lines) were treated with avelumab, axitinib, and palbociclib (3+3 dose escalation design). Tumor and normal endobronchial mucosal biopsies were obtained on all patients for retrospective SIMS algorithm validation. Results: Fifteen patients were treated: 6 at dose level 1 (DL1); 6, dose level 2 (DL2); 3, dose level 3 (DL3). Three dose-limiting toxicities (DLTs) at least possibly drug-related occurred: 1 DLT at DL2 (Grade 3 (G3) infusion reaction); 2 patients with DLTs at DL3 (1 with G3 hand/foot syndrome and G3 fatigue and 1 with G5 respiratory failure). Among 14 evaluable patients, the partial response (PR) rate was 28.6% (4/14 patients including 2/6 patients at DL1; two PRs in patients who failed prior pembrolizumab; two PRs in patients with PD-L1 < 1%). The maximum tolerated dose was avelumab 10 mg/kg IV q2weeks, axitinib 5 mg PO BID continuous, palbociclib 75 mg PO daily on days 8-28 of a 28 day cycle (DL2). DL2 was above the recommended phase II dose (RP2D), since 5/6 patients treated at DL2 required later treatment delays and/or dose reductions, mostly due to neutropenia. To further evaluate DL1, 3 patients were added to this cohort (total of 6). Since no DLTs were seen at DL1, and 5 of 6 patients did not require dose reduction, DL1 (avelumab 10 mg/kg IV q2weeks, axitinib 3 mg PO BID continuous, palbociclib 75 mg PO daily on days 8-28 of a 28 day cycle) is the RP2D. Conclusions: The RP2D was determined to be dose level 1. This triplet showed antitumor activity in patients with NSCLC, including those progressing on prior pembrolizumab. SIMS algorithm correlates of response are being assessed. Clinical trial information: NCT03386929 .

e19392 Background: The treatment landscape for advanced renal cell carcinoma (RCC) has transformed in the past two years. Both Nivolumab plus Ipilimumab and Pembrolizumab plus Axitinib are approved regimens for first-line treatment of intermediate to poor-risk patients with advanced RCC. The choice between these immunotherapy-based combinations for first-line therapy is highly debated; no prior study has evaluated the cost-effectiveness of both combinations compared to Sunitinib. Methods: We used a decision analytic Markov model informed by the recent Checkmate-214 and Keynote-426 phase 3 randomized controlled clinical trials to evaluate costs and effectiveness of Nivolumab plus Ipilimumab, Pembrolizumab plus Axitinib, and Sunitinib in the first-line treatment of advanced RCC from a US health payer perspective. We used the model to extrapolate survival beyond the closure of the trials and examined the robustness of our findings with sensitivity analyses. Main outcomes were life expectancy, quality-adjusted life years (QALYs), costs, and incremental cost-effectiveness ratios, all discounted at 3% annually. Results: Nivolumab plus Ipilimumab increased life expectancy by 0.58 years at cost of approximately $190,000 per QALY gained compared to Sunitinib. Pembrolizumab plus Axitinib increased life expectancy by 0.39 years at a cost of approximately $861,000 per QALY gained compared to Nivolumab plus Ipilimumab. The results were not sensitive to reasonable changes in drug costs and quality of life estimates. Both combinations cost more than the traditional willingness-to-pay threshold (WTP) of $150,000 per QALY gained. A 20% price reduction is required for Nivolumab and Ipilimumab to be cost-effective and a 48% price reduction is required for Pembrolizumab plus Axitinib to be cost-effective. Conclusions: Both Nivolumab plus Ipilumumab and Pembrolizumab plus Axitinib provide increased longevity and reduced morbidity relative to Sunitinib. However, the prolonged duration of treatment and doublet-drug pricing results in high-costs. Price reductions are required for both of the immunotherapy-based combinations to be cost-effective. [Table: see text]

687 Background: Patients (pts) with brain metastasis from renal cell carcinoma (RCC) have poor prognosis and are often excluded from randomized registrational trials. The phase 3 JAVELIN Renal 101 trial (NCT02684006) demonstrated significantly improved progression-free survival (PFS) for A+Ax vs S in pts with advanced RCC (Motzer NEJM 2019). The activity of A+Ax in pts with brain metastasis enrolled in JAVELIN Renal 101 is presented. Methods: PFS was compared between treatment arms for the subgroup of pts randomized in JAVELIN Renal 101 with brain metastases at enrollment (pts with brain disease site prior to randomization by blinded independent central review [BICR] or by investigator assessment). PFS time was summarized per BICR assessment by treatment arm using the Kaplan-Meier method. The Cox proportional hazards model was fitted to compute the hazard ratio (HR) and the corresponding CI. In addition, time to brain metastasis was assessed for pts without brain metastasis by BICR at enrollment after treating death as a competing risk. Results: Of all randomized pts (A+Ax arm, N=442; S, N=444), 23 in each arm (5.2%) had asymptomatic brain metastasis at enrollment; of these, pts assigned to A+Ax had a PFS of 4.9 mo (95% CI: 1.6, 5.7) vs 2.8 mo (95% CI: 2.3, 5.6) for pts assigned to S (HR: 0.90; 95% CI: 0.43, 1.88). Among pts without brain metastasis at enrollment, 8 pts on the A+Ax arm and 10 on the S arm developed brain metastasis during the trial, based on BICR assessment; 17/18 occurred ≤12 mo from randomization. The cumulative incidence rate of brain metastasis at 18 mo was 2% (95% CI: 0.6, 3.3) for the A+Ax arm and 3% (95% CI: 1.1, 4.8) for the S arm. Conclusions: In this post hoc exploratory analysis of JAVELIN Renal 101, the observed PFS among pts with brain metastasis at enrollment was similar between the two arms, with HR and median PFS numerically favoring A+Ax. Pts on the S arm had a numerically higher incidence of new brain metastases on trial. Outcomes are poor in pts with advanced RCC and brain metastasis; more effective treatments are needed. Clinical trial information: NCT02684006.

716 Background: Pembrolizumab/axitinib significantly prolonged progression-free survival (PFS) and overall survival (OS) vs. sunitinib in a phase 3 trial KEYNOTE-426 among previously untreated patients with advanced renal cell carcinoma (RCC). This study assessed the cost-effectiveness of pembrolizumab/axitinib vs. other first-line treatments of advanced RCC from a US payer perspective. Methods: A partitioned survival model with 3 states (progression-free, progressed, death) evaluated costs and quality-adjusted life years (QALYs) for pembrolizumab/axitinib and other first-line regimens: sunitinib and pazopanib in the overall population; sunitinib, cabozantinib, and nivolumab/ipilimumab in the subgroup with poor/intermediate IMDC risk. Time on treatment, PFS, and OS were extrapolated using parametric models fitted to KEYNOTE-426 data (24 Aug 2018 cutoff) for pembrolizumab/axitinib and sunitinib, and hazard ratios from network meta-analyses for other comparators. Costs of first-line and subsequent treatment, adverse events, medical resources, and terminal care were estimated based on trial results, drug labels, and published sources. Utilities were derived through mixed-effects regressions of KEYNOTE-426 EQ-5D data. Results: Over a lifetime, the incremental cost-effectiveness ratios (ICERs) for pembrolizumab/axitinib were below willingness-to-pay thresholds of $150,000/QALY or $180,000/QALY (approx. 3 × gross domestic product per capita) vs. all comparators in the overall and intermediate/poor risk populations (table). Results were robust in deterministic and probabilistic sensitivity analyses. Conclusions: Pembrolizumab/axitinib is associated with higher QALYs and considered cost-effective vs. other first-line treatments of advanced RCC in the US.[Table: see text]

TPS762 Background: The combination of avelumab plus axitinib has been recently reported to be superior than sunitinib alone for treatment of previously untreated mRCC patients (Motzer, NEJM 2019). The study reported a median PFS of 13.8 for the combination of avelumab plus axitinib compared to 8.4 months for sunitinib (p

32 Background: Avelumab, an anti–PD-L1 monoclonal antibody, was recently approved for the treatment of aRCC in combination with axitinib and was previously indicated for the treatment of metastatic Merkel cell carcinoma (MCC) and platinum-treated advanced/metastatic urothelial carcinoma (UC). Although avelumab was approved with weight-based dosing (10 mg/kg intravenously [IV] every 2 weeks [Q2W]), it was subsequently approved for flat dosing (800 mg IV Q2W) based on population pharmacokinetic (popPK), exposure-efficacy and exposure-safety modeling and simulations in MCC and UC (Novakovic AM, et al. Clin Pharmacol Ther. 2019). The justification for the recommended flat-dose regimen for avelumab as combination therapy with axitinib in aRCC is presented. Methods: Simulated exposure metrics (eg, area under the curve) from the previous popPK model (data from 1,827 patients with solid tumors across 3 clinical trials) for both weight-based and flat-dose regimens were compared with the exposure metrics obtained from treatment-naive patients with aRCC enrolled in 2 clinical studies (N = 488 from NCT02493751 and NCT02684006) who received avelumab (10 mg/kg Q2W) + axitinib (5 mg orally twice daily). Avelumab exposure-response relationships for safety and efficacy were also analyzed. Endpoints included grade ≥3 treatment-emergent adverse events (TEAEs), any-grade infusion-related reactions (IRRs) and immune-related (ir)AEs, and progression-free survival (PFS) by independent review. Results: The administration of weight-based dosing of avelumab in the aRCC population yielded similar PK exposures to simulated reference exposures of the flat-dose regimen in the solid tumor population. Avelumab exposure was not associated with increased probabilities of grade ≥3 TEAEs or IRRs, although there was a weak association with an increased probability of any-grade irAEs. Conclusions: The similar exposures observed for both avelumab dosing regimens in aRCC, and in prior studies in the MCC and UC populations, suggest that the 800 mg Q2W flat-dose regimen will maintain the benefit-risk ratio for avelumab + axitinib for treatment-naive patients with aRCC. Clinical trial information: NCT02493751 . Clinical trial information: NCT02684006.

5078 Background: Strategies integrating androgen targeted and locoregional therapies are being increasingly used in PCa with regional spread, but are rarely curative. Angiogenesis inhibitors delay progression in castration resistant PCa and may synergize with ADT through endothelial cell apoptosis in hormone naïve patients (pts). We hypothesized that the frontline combination of ADT with the potent VEGF inhibitor Axi would improve PCa control relative to ADT alone and allow for meaningful time off systemic therapy after surgical consolidation. Methods: Pts with either clinically detected LN+ (TxN1M0 or TxNxM1a) or very high risk for LN PCa were treated with ADT for 2 mos and then randomized 2:1 to respectively add open label Axi (5 mg PO bid) vs. continue ADT alone for 4 mos until surgery. Those responding with PSA ≤5 ng/mL were offered prostatectomy and extended pelvic lymphadenectomy (RP). ADT +/- Axi was withheld postoperatively and PSA measured q3 mos until 1 y. Primary objective: proportion of pts progression free (FFP) 12 mos after RP, defined as PSA ≤1.0 ng/mL and no radiation or ADT, aiming to detect a 35% difference favoring ADT+Axi. Results: 72 pts completed accrual. We report on the 54 pts with LN+ disease: median age 62 y (range 42-76), pretreatment PSA 22.9 ng/mL (range 3.6 - 404.4), 38 N1 / 16 M1a. Table shows presurgical therapy outcomes. Path responses in the prostate were similar between arms, but in 5 ADT+Axi vs. 0 ADT LN+ pts there was no residual nodal disease. Testosterone recovery: 24/26 ADT+Axi and 9/9 ADT RP pts by 6 mos. 21/36 ADT+Axi and 15/18 ADT pts have failed; 1 y FFP estimates 48.0% (SE 8.6%) and 16.7% (SE 8.3%), respectively (p = 0.02). 1 y undetectable PSA 9 pts (6 ADT+Axi). No grade 4 toxicities or unexpected side-effects were observed. Conclusions: 1 year after RP, ADT+Axi resulted in proportionally greater number of LN+ PCa pts off treatment and progression free than ADT alone. Tissue analysis is evaluating predictors of benefit to further develop angiogenesis inhibition as part of combination strategies for hormone naïve PCa. Clinical trial information: NCT01409200. [Table: see text]

4567 Background: Drug combinations targeting vascular endothelial growth factor (VEGF) and the programmed death one (PD-1) pathway have demonstrated encouraging efficacy in patients (pts) with mRCC. We are conducting a phase I/II trial combining the VEGF-targeting tyrosine kinase inhibitor (TKI) axi and the PD-1 inhibitor nivo in mRCC pts. Methods: The phase I portion of this investigator-initiated, multi-center trial enrolled pts with TKI-refractory mRCC (any line) and no prior anti-PD-1. It used a 3+3 design, with axi dosing starting at 3 mg orally BID, escalating to a target dose of5 mg BID. Nivo dosing was fixed at 240 mg IV Q2 weeks or 480 mg Q4 weeks. Eligible pts received axi alone for a one week induction, followed by combination dosing. There was a 4 week period to assess for dose limiting toxicities (DLTs). The primary endpoint for phase I was safety and establishment of a recommended phase II dose (RP2D) for axi. Safety and early efficacy data for the phase I cohort are presented. Results: Twelve pts received treatment during the phase I portion, with all evaluable for toxicity. Ten were 2nd line and 2 were 3rd line or beyond. One DLT was noted in the first cohort of three pts (grade 3 autoimmune disorder), thus that cohort was expanded. No further DLTs were reported at axi 3 mg BID, or at further expansion to 5 mg BID. Grade 3 adverse events (AEs) at least possibly related to one of the drugs included expected side effects HTN, hyperglycemia, and transaminitis. One patient received steroids for an immune related AE (grade 3 transaminitis) that resolved to grade 1 with steroids. No grade 4-5 AEs occurred. Axi at 5 mg BID was chosen as the RP2D. With 10 pts evaluable for efficacy, 4 pts had partial responses, 4 pts had stable disease, and 2 had progressive disease. Updated efficacy data will be presented. Conclusions: The phase I portion of this phase I/II trial has demonstrated expected safety and established 5 mg BID as the RP2D axi dose. This ongoing VEGF TKI/PD1 trial incorporating two drugs already approved for mRCC pts has shown encouraging signs of efficacy and has now expanded to include treatment naïve pts in addition to TKI-refractory pts as part of phase II. Clinical trial information: NCT03172754.

e16097 Background: Inhibitors of the vascular endothelial growth factor (VEGF), its receptor (Ri) or mammalian target of rapamycin (mTORi) are components of systemic treatment in metastatic renal cell carcinoma (mRCC) and are applied in sequence. We compared the efficacy of VEGFRi and mTORi in 2nd line after failure of bevacizumab/interferon in a phase II trial. Methods: Key inclusion criteria were: measurable mRCC (all histologies), ECOG 0-1, IMDC risk: good or intermediate, adequate organ function. Tumor status was assessed in week 11 and q12 wks., thereafter. Measures of Health-related quality of life (HR-QoL) utilized FKSI-10 and was assessed in week 4, 10 and q12 wks., thereafter. 1st line consisted of bevacizumab 10mg/kg q2wks. + interferon 9*106 IE 3x/week (BEV/IFN). Upon progression or intolerance, patients were re-screened and randomized between VEGFRi (axitinib 5 mg BID, dose-escalation permitted; sunitinib 50 mg OD, 4-2 regimen) and everolimus (EVE) treatment (10 mg OD). Cross-over occurred at time of progression or intolerance. Improvement of 2nd line PFS-rate at 6 mo. from 50% to 65% was the primary endpoint. Secondary endpoints were PFS, total PFS, ORR, OS, safety and HR-QoL. Results: Between November 2012 and June 2015 a total of 22 of 100 patients were included and at that time stopped for poor accrual. 10 pts. (46%) were randomized to receive 2nd line treatment with everolimus (n = 5) or VEGFRi (n = 5). At study entry (2/10) 20% had nephrectomy. ECOG 0 was recorded in 20% (EVE) and 60% (VEGFRi), respectively. Objective response rate (ORR) to 1st line BEV/IFN was 20%. In 2nd line treatment all patients experienced adverse events (AE). Grade ≥3 AEs occurred in 2/5 (40%) (EVE) and 4/5 (80%) (VEGFRi) pts., respectively. SAEs occurred in 3/5 (60%) in each arm. ORR was 1/5 (20%) for axitinib and 0/5 (0%) for EVE. PFS rate at 180 days was 20% in each arm. Median PFS was 3.7 (EVE) and 2.2 mo. (VEGFRi) HR 1.0 (95%CI 0.26-3.85; p = 0.997). OS was comparable between arms HR 1.12 (95%CI 0.27-4.61; P = 0.872). 7 pts. crossed over to 3rd line treatment. Conclusions: The small number of pts. randomized to EVE or VEGFRi is a major limitation of our trial, but may mirror the current change of treatment reality. However, no significant difference was detected for the PFS rate at 6 mo., indicating the limited activity of EVE or VEGFRi in 2nd line treatment. Clinical trial information: NCT01731158.

4573 Background: The ATLAS trial compared axitinib vs placebo in patients (pts) with locoregional RCC at risk of recurrence after nephrectomy. ATLAS was stopped due to futility at a pre-planned interim analysis; results showed no difference in disease-free survival (DFS) between the treatment arms. We explored whether pts treated longer with axitinib achieved better outcomes and the impact of axitinib dose reduction or increase on DFS – the trial required dose reduction for toxicity and allowed dose escalation in the event of no or minimal toxicity. Methods: Pts in ATLAS received a maximum of 3 y of study treatment. A landmark analysis was conducted comparing pts treated with axitinib ≤1 y vs > 1 y. Pts who recurred or censored prior to 1 y were excluded. An analysis of daily dose characteristics was undertaken to compare patients whose dose was reduced and whose dose was increased to those with a stable dose of axitinib. Cox proportional hazard model was used for DFS analysis. Toxicity analysis using a 90-day landmark was also conducted. Results: Overall, 264 axitinib-treated pts were included in this analysis. Of these 42 pts were treated for ≤1 y and 222 pts for > 1 y. Pts remaining on axitinib > 1 y vs ≤1 y did not have different DFS (hazard ratio [HR] = 0.572, 95% confidence interval [CI]: 0.247–1.327, P= 0.1874). Pts with dose reduction had longer DFS than those with a stable dose (HR = 0.458, CI: 0.305–0.687, P= 0.0001). Pts with dose increase did not have DFS different to stable dose pts (HR = 1.936, CI: 0.937–3.997, P= 0.0685). No difference in DFS in pts experiencing grade ≥2 adverse events (AEs) vs grade < 2 AEs within 90 d of start of treatment was observed (HR = 0.885, CI: 0.419–1.869, P= 0.7488). Pts experiencing grade ≥3 AEs within 90 d of start of treatment had shorter DFS compared to those that did not (HR = 1.643, CI: 0.963–2.801, P= 0.0653). Conclusions: DFS did not vary based on duration of axitinib treatment, however, pts with dose reductions had longer DFS vs pts with stable dose or dose increases. This difference suggests that there is a relation between axitinib exposure and DFS as seen with sunitinib in the advanced setting and pazopanib in the PROTECT study.

4072 Background: Combining an immune checkpoint inhibitor with a targeted antiangiogenic agent may leverage complementary mechanisms of action for treatment of advanced/metastatic (a/m) hepatocellular carcinoma (HCC). Avelumab is a human anti–PD-L1 IgG1 antibody with clinical activity in various tumor types; axitinib is a tyrosine kinase inhibitor selective for VEGF receptors 1/2/3. VEGF Liver 100 (NCT03289533) is a phase 1b study evaluating safety and efficacy of avelumab + axitinib in treatment-naive patients (pts) with HCC; interim results are reported here. Methods: Eligible pts had confirmed a/m HCC, ≥1 measurable lesion, a fresh or archival tumor specimen, ECOG PS ≤1, and Child-Pugh class A. Pts received avelumab 10 mg/kg IV Q2W + axitinib 5 mg orally BID until progression, unacceptable toxicity, or withdrawal. Endpoints included safety and objective response (RECIST v1.1; modified [m] RECIST for HCC). Results: Interim assessment was performed after a minimum follow up of 6 months based on the released study data set (clinical cut-off date: Aug 1, 2018). As of the cut-off date, 22 pts (median age: 68.5 y) were treated with avelumab (median: 20.0 wk) and axitinib (median: 19.9 wk). The most common grade 3 treatment-related adverse events (TRAEs) (≥10% of patients) were hypertension (50.0%) and hand-foot syndrome (22.7%); no grade 4/5 TRAEs were reported. Immune-related AEs (irAEs) (≥10% of pts) were hypothyroidism (31.8%) and hyperthyroidism (13.6%). No grade ≥3 irAEs were reported; no pts discontinued treatment due to TRAEs or irAEs. Based on Waterfall plot calculations, tumor shrinkage was observed in 15 (68.2%) and 16 (72.7%) pts by RECIST and mRECIST, respectively. ORR was 13.6% (95% CI, 2.9%-34.9%) and 31.8% (95% CI, 13.9%-54.9%) by RECIST and mRECIST, respectively. OS data were immature at data cutoff. Conclusions: The preliminary safety of avelumab + axitinib in HCC is manageable and consistent with the known safety profiles of avelumab and axitinib when administered as monotherapies. This study demonstrates antitumor activity of the combination in HCC. Follow-up is ongoing. Clinical trial information: NCT03289533. [Table: see text]

101 Background: The phase 3 JAVELIN Renal 101 trial in previously untreated patients (pts) with aRCC demonstrated a progression-free survival (PFS) benefit and higher objective response rate with A+Ax vs S (Motzer, ESMO 2018; LBA6_PR). Here, we report outcomes from biomarker analyses of baseline tumor samples. Methods: We correlated efficacy with the results of molecular analyses of tissue samples from all 886 pts enrolled in JAVELIN Renal 101. Nephrectomy or tumor samples were characterized by immunohistochemistry (CD8 and PD-L1), whole-exome sequencing (WES), and RNAseq. WES and RNAseq were used to examine somatic mutations and analyze relevant gene expression signatures (GES) in relation to clinical outcomes. GES analyses included published and de novo signatures: effector T cell (Teff), angiogenesis (angio),T cell-inflamed (Tinf), and a novel immune-related signature incorporating pathway indicators for T- and NK-cell activation and IFNγ signaling, among others. Results: PD-L1 expression (≥1% immune cells) was associated with the longest PFS in the A+Ax arm and the shortest in the S arm (HR, 0.63; 95% CI, 0.49, 0.81). Significant treatment arm–specific differences in PFS were observed relative to wildtype when mutations in genes such as CD1631L, PTEN, or DNMT1 were present. Tumor mutational burden did not distinguish pts with respect to PFS. High-angio GES was associated with significantly improved PFS in the S arm but did not differentiate PFS in the A+Ax arm. In the low-angio subset, A+Ax improved PFS vs S. Pts with high Teff and Tinf in the A+Ax arm had longer PFS vs the S arm. In the A+Ax arm, PFS was enhanced in patients with immune GES–positive tumors vs those in the negative group (HR, 0.63; 95% CI, 0.46, 0.86; 2-sided p = 0.004), as well as in an independent dataset (JAVELIN Renal 100; Choueiri, Lancet Oncol, 2018) (HR, 0.46; 95% CI, 0.20, 1.05; 2-sided p = 0.064). Updated efficacy, including overall survival, will be presented. Conclusions: These findings define molecular features that differentiate therapy-specific outcomes in first-line aRCC and may inform personalized therapy strategies for pts with aRCC. Funding: Pfizer and Merck KGaA. Clinical trial information: NCT02684006.

4500 Background: In KEYNOTE-426, pembro + axi significantly improved OS (HR 0.53, P < .0001), PFS (HR 0.69, P = .0001), and ORR (59.3% vs 35.7%, P < .0001) vs sunitinib and had manageable toxicity as first-line therapy for mRCC (NCT02853331). The pembro + axi benefit was observed across all IMDC risk groups and regardless of PD-L1 expression. We present data for the combined intermediate/poor risk group and for patients (pts) with sarcomatoid features. Methods: 861 eligible pts with clear-cell mRCC, no prior systemic therapy for mRCC, and KPS ≥70 were randomized 1:1 to pembro 200 mg IV Q3W for a maximum of 35 cycles plus axi 5 mg orally BID (N = 432) or sunitinib 50 mg orally QD (4-wk on/2-wk off) (N = 429). Primary endpoints were OS and PFS (RECIST v1.1 by blinded, independent central review [BICR]). ORR (RECIST v1.1 by BICR) was the key secondary endpoint. The intermediate/poor risk group was prespecified; the sarcomatoid group was exploratory. HRs and their 95% CIs were calculated with a Cox proportional hazards model. None of the analyses were multiplicity-controlled. Results: 592 (68.8%) of all randomized pts were of IMDC intermediate/poor risk — 294 in the pembro + axi arm, 298 in the sunitinib arm. Pembro + axi improved OS (HR 0.52, 95% CI 0.37-0.74; 12-mo rate 87.3% vs 71.3%), PFS (HR 0.67, 95% CI 0.53-0.85; median 12.6 vs 8.2 mo), and ORR (55.8% [95% CI 49.9-61.5] vs 29.5% [24.4-35.1]) in pts with intermediate/poor risk; CR rates were 4.8% (95% CI 2.6-7.9) vs 0.7% (0.1-2.4). Of the 578 pts with known status, 105 (18.2%) had sarcomatoid features — 51 in the pembro + axi arm, 54 in the sunitinib arm. Pembro + axi improved OS (HR 0.58, 95% CI 0.21-1.59; 12-mo rate 83.4% vs 79.5%), PFS (HR 0.54, 95% CI 0.29-1.00; median not reached vs 8.4 mo), and ORR (58.8% [95% CI 44.2-72.4] vs 31.5% [19.5-45.6]) in pts with sarcomatoid features; CR rates were 11.8% (95% CI 4.4-23.9) vs 0% (0.0-6.6). Conclusions: Pembro + axi provides benefit in the combined population of pts with IMDC intermediate or poor risk and in pts whose tumors had sarcomatoid features. The observed benefits were consistent with those seen in the total population. Clinical trial information: NCT02853331.

614 Background: Axitinib (axi) is approved for 2nd-line treatment of aRCC. In AXIS trial, median progression-free survival (PFS) was significantly longer in axi- vs sorafenib (sor)-treated pts (hazard ratio [HR] 0.67, 95% CI 0.54–0.81, P

616 Background: Sarcomatoid renal cell carcinoma (SRCC) is a rare but very aggressive type of RCC. The treatment option for SRCC is very limited, and there have been anecdotal reports of very good responders to gemcitabine or vascular endothelial growth factor receptor tyrosine kinaase inhibitors (VEGFR TKI). We conducted multicenter phase 2 trial of gemcitabine plus axitinib (GX) in patients (pts) with recurrent or metastatic SRCC to evaluate its efficacy and safety. Methods: Eligibility criteria included histologically confirmed metastatic or recurrent RCC with sarcomatoid component of 25% or more on resected kidney or exclusive sarcomatoid carcinoma on needle biopsy, ECOG PS 0-2, measurable lesion by RECIST v1.1, and adequate cardiac, hepatic, renal and bone marrow function. Pts with uncontrolled hypertension, prior exposure to gemcitabine or VEGFR TKI were exclude. Pts received gemcitabine 1,000 mg/m2 intravenously on days 1 and 8 by 3-week cycle and axitinib 5 mg twice daily. The primary endpoint was objective response rate (ORR) according to RECIST v1.1, and secondary end points were progression-free survival (PFS), overall survival (OS), and toxicity. Results: Twenty-five pts were enrolled between Oct 2014 and Aug 2018. Median age was 61 (range 33-80), and 84% was male. ECOG PS were 1 (92%) and 2 (8%), and 52% had prior nephrectomy. Clear cell carcinoma was the most common histology of carcinoma component, and median percentage of sarcomatoid component was 90% (25-100%). Pts belonged to intermediate (28%) and poor (72%) risk group according to IMDC risk stratification. Median 6 cycles of GX were administered, and 56%, 28%, and 12% of pts achieved PR, SD, and PD, respectively, with an ORR of 56% and median duration of response of 2.5 months. With a median follow-up duration of 21.4 mo, median PFS was 4.9 mo (95% CI, 3.5-13.3), and median OS was 8.4 months (95% CI 3.5-13.3 months). Most adverse events were manageable, and no unexpected toxicities were found. One pt died of grade 5 pneumonia. Conclusions: GX showed promising efficacy in pts with SRCC. GX might be considered as one of treatment options for pts with SRCC, although efficacy of GX should be confirmed in larger trial.

660 Background: The overexpression of hypoxia induced factor 1a/2a in ccRCC leads to up-regulation of vascular endothelial growth factor (VEGF) that results in increased angiogenesis, tumor metastasis, and treatment resistance. Using several preclinical xenograft models, it has been demonstrated that therapeutic doses of the selenium-containing molecules, seleno-L-methionine (SLM) and methylselenocysteine (MSC) caused enhanced degradation of HIF1α/2α, down-regulation of oncogenic miRNA-210 and 155, up-regulation tumor suppressor miRNA-664 and LET-7b, and stabilization of tumor vasculature, yielding higher tumor drug uptake and protection from toxic side effects when combined with chemotherapeutic and VEGF-targeted agents. Methods: This is a phase I (3+3 design) dose finding trial of SLM (2500, 3000 or 4000 µg) given orally twice daily for 14 days, followed by once a day in combination with standard dose axitinib to patients with metastatic RCC. Primary endpoint is safety. Secondary endpoint is efficacy including overall response rate (ORR), progression free survival (PFS) and overall survival (OS). Results: To date, 12 evaluable patients (pts) with metastatic RCC who progressed on one or more prior lines of treatment were enrolled. The first 3 pts were treated at 4000 µg, the second and third 3 pts were treated at 2500 and 3000 µg respectively. Additional 3 pts were added to 4000 µg. No dose limiting toxicity (DLT) was seen. Most common AEs included fatigue, diarrhea, hypertension, nausea, anorexia, cough, proteinuria and weight loss. Of the 4000 µg cohort, 2 pts achieved CR with ongoing responses at 31 and 29 months, 1 pt had PR for 24 months and 1 had PD at 3 months, 2 pts are not assessed yet. Of the 2500 µg cohort, 1 pt with ongoing PR for 21 months, 1 pt had stable disease for 6 months, and 1 pt had PD at 2 months. The 3000 µg cohort, one pt has ongoing PR for 12 months; another pt had PR lasting 10 months, the 3rd pt had SD for 4 months. Conclusions: High dose SLM is safe in combination with axitinib, with promising efficacy. Further data including biomarkers will be presented at the meeting. Clinical trial information: NCT02535533.

555 Background: No previous study has compared the efficacy and safety of first-line axitinib and sunitinib. We aimed to compare oncological outcomes and safety of axitinib and sunitinib in patients with treatment-naïve metastatic renal cell carcinoma (mRCC). Methods: We retrospectively evaluated 169 patients with mRCC who were treated with axitinib or sunitinib as the first-line therapy in five hospitals between October 2008 and August 2018.Oncological outcomes and safety were compared between axitinib (n = 68) and sunitinib (n = 101) groups. Inverse probability of treatment weighted (IPTW)-adjusted Cox regression analysis was performed to evaluate effects of first-line therapies on progression-free survival (PFS), cancer-specific survival (CSS), and overall survival (OS). Results: Patients in the axitinib group were significantly older (66 vs 72 years) than those in the sunitinib group. Median relative dose intensity was significantly higher in the axitinib group (94 ± 62%) than in the sunitinib group (65 ± 20%; P = 0.001). Objective response rate was significantly higher in the axitinib group (21%) than in the sunitinib group (10%; P = 0.042). IPTW-adjusted Cox regression analysis revealed significant differences in CSS and OS but not in PFS between the two groups. Safety in terms of grade ≥3 adverse events was significantly different between the axitinib (34%) and sunitinib (55%) groups ( P = 0.006). Conclusions: Compared with sunitinib, axitinib significantly prolonged CSS and OS and showed a safer profile as the first-line therapy for treatment-naïve mRCC.

ADONIS is an ongoing observational study in 9 European countries, designed to evaluate treatment patterns/outcomes in patients with metastatic renal cell carcinoma (mRCC) treated with first-line sunitinib and/or second-line axitinib post sunitinib. We present an evaluation of sunitinib efficacy by risk group, in the real-world setting examined in ADONIS.Patients were enrolled at the start of first-line sunitinib treatment or second-line axitinib post sunitinib treatment. Evaluation of sunitinib efficacy was assessed by International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) and Memorial Sloan Kettering Cancer Center risk criteria.For all patients in this analysis (N = 467), the median progression-free survival was 23.8 months (95% confidence interval [CI], 16.5-28.5 months), 11.8 months (95% CI, 8.1-17.4 months), and 4.6 months (95% CI, 2.5-7.7 months) for IMDC favorable-, intermediate-, and poor-risk groups, respectively. The median overall survival was 97.1 months (95% CI, 46.3 months-not evaluable [NE]), 33.5 months (95% CI, 20.5-46.6 months), and 10.0 months (95% CI, 4.5-19.8 months) for the respective risk groups. Data on individual risk factors were available for a subgroup of patients, allowing analysis by intermediate risk by 1 versus 2 risk factors. When including this subgroup (n = 120), the median overall survival for IMDC favorable-, intermediate-1, and intermediate-2 risk factors was 21.6 months (95% CI, 16.3 months-NE), 20.5 months (15.5 months-NE), and 15.1 months (4.1 months-NE), respectively.For patients overall and by risk-group stratification, survival estimates were aligned with previously published data. In patients with intermediate-1 risk, overall survival was very similar to patients with favorable risk. However, further exploration of outcome data from different sources is needed to confirm these observations.

543 Background: A phase 1b study of pembro (anti–PD-1) plus axi (VEGFR-TKI) showed promising antitumor activity and manageable safety in patients (pts) with previously untreated mRCC. The global, open-label, phase 3 KEYNOTE-426 study assessed the efficacy and safety of pembro + axi vs sunitinib as first-line therapy for mRCC (NCT02853331). Methods: Eligible pts with clear-cell mRCC, no previous systemic therapy for mRCC, and KPS ≥70% were randomized 1:1 to pembro 200 mg IV Q3W for a maximum of 35 cycles plus axi 5 mg orally BID or sunitinib 50 mg orally QD (4-wk on/2-wk off schedule). Treatment was given until PD, intolerable toxicity, or pt/investigator decision. Randomization was stratified by IMDC risk group and geographic region. Primary endpoints were OS and PFS (RECIST v1.1 by blinded, independent central review [BICR]). ORR was the key secondary endpoint. At the protocol-specified first interim analysis, the superiority thresholds were P = 0.0001 for OS, 0.0013 for PFS, and 0.025 for ORR (if OS and PFS were significant). Results: 861 pts were randomized: 432 to pembro + axi, 429 to sunitinib. After a 12.8-mo median follow-up, 59.0% of pts in the pembro + axi arm and 43.1% in the sunitinib arm remained on treatment. Pembro + axi significantly improved OS (HR 0.53 [95% CI 0.38-0.74]; P < 0.0001; 12-mo rate 89.9% vs 78.3%), PFS (HR 0.69 [95% CI 0.57-0.84]; P = 0.0001; median 15.1 vs 11.1 mo), and ORR (59.3% vs 35.7%; P < 0.0001). Duration of response was prolonged with pembro + axi (median not reached vs 15.2 mo). The pembro + axi benefit was observed in all subgroups tested, including all IMDC risk and PD-L1 expression subgroups. Treatment-related AEs were grade 3-5 in 62.9% of pts in the pembro + axi arm vs 58.1% in the sunitinib arm and led to regimen discontinuation in 6.3% vs 10.1%. Conclusions: Pembrolizumab + axitinib provided superior OS, PFS, and ORR compared with sunitinib and had manageable safety in pts with previously untreated, advanced or metastatic clear-cell RCC. These data suggest that pembrolizumab + axitinib should be a new standard of care for this population. Clinical trial information: NCT02853331.

Background: Axitinib has been suggested to be effective as a second line treatment of metastatic renal cell carcinoma. However, its adoption may be limited by its financial consequences. Therefore, a cost-utility analysis was conducted to estimate the economic value of axitinib as a second line treatment of metastatic renal cell carcinoma. Aim: This analysis will informed the decision makers on the potential use of axitinib in this population within the Ministry of Health facilities. Methods: A state transition model was developed using Microsoft Excel 2010 to simulate a hypothetical cohort of patient receiving axitinib or best supportive care over 5 years of time horizon. A monthly cycle was chosen without a half cycle correction. Three health states were included in the model as progression free, disease progression and dead. A 3% discount rate was applied as recommended in the Pharmacoeconomic Guidelines for Malaysia. Total costs were estimated using unit costs from local sources and published data. The clinical and utility parameters were derived from the published literatures. Results: The mean probabilistic incremental discounted cost and QALY for axitinib were RM 113,576.29 and 0.35413 respectively, yielded a probabilistic incremental cost-effectiveness ratio (ICER) of RM 320,719. Unavailability of the local price for axinitib may play a part in the higher estimation of ICER. Conclusion: Axitinib may not be considered as a cost-effective second line treatment of metastatic renal cell carcinoma as the ICER is beyond the value of 3 GDP per capita.

11547Background: Inhibition of programmed-death 1 (PD1) by pembrolizumab (P) produced overall response rates (ORR) of 19% in advanced STS [SARC028]. Vascular endothelial growth factor (VEGF) suppre...