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PURPOSE Effective treatments are needed for melanoma that progresses on inhibitors of programmed cell death protein-1 (PD-1) or its ligand (PD-L1). We conducted the phase II LEAP-004 study to evaluate the combination of the multikinase inhibitor lenvatinib and the PD-1 inhibitor pembrolizumab in this population (ClinicalTrials.gov identifier: NCT03776136 ). METHODS Eligible patients with unresectable stage III-IV melanoma with confirmed progressive disease (PD) within 12 weeks of the last dose of a PD-1/L1 inhibitor given alone or with other therapies, including cytotoxic T-cell lymphocyte–associated antigen 4 (CTLA-4) inhibitors, received lenvatinib 20 mg orally once daily plus ≤ 35 doses of pembrolizumab 200 mg intravenously once every 3 weeks until PD or unacceptable toxicity. The primary end point was objective response rate (ORR) per RECIST, version 1.1, by independent central review. RESULTS A total of 103 patients were enrolled and treated. The median study follow-up was 15.3 months. ORR in the total population was 21.4% (95% CI, 13.9 to 30.5), with three (2.9%) complete responses and 19 (18.4%) partial responses. The median duration of response was 8.3 months (range, 3.2-15.9+). ORR was 33.3% in the 30 patients with PD on prior anti–PD-1 plus anti–CTLA-4 therapy. The median progression-free survival and overall survival in the total population were 4.2 months (95% CI, 3.8 to 7.1) and 14.0 months (95% CI, 10.8 to not reached), respectively. Grade 3-5 treatment-related adverse events occurred in 47 (45.6%) patients, most commonly hypertension (21.4%); one patient died from a treatment-related event (decreased platelet count). CONCLUSION Lenvatinib plus pembrolizumab provides clinically meaningful, durable responses in patients with advanced melanoma with confirmed PD on prior PD-1/L1 inhibitor-based therapy, including those with PD on anti–PD-1 plus anti–CTLA-4 therapy. The safety profile was as expected. These data support lenvatinib plus pembrolizumab as a potential regimen for this population of high unmet need.

OBJECTIVES Parts 4 and 5 of the phase 1/2 KEYNOTE-022 study investigated the maximum tolerated dose (MTD), safety, and efficacy of pembrolizumab plus trametinib in solid tumours and BRAF wild-type melanoma. PATIENTS AND METHODS Patients received intermittent or concurrent dosing of pembrolizumab plus trametinib. Concurrent dosing was 2 or 4 weeks of trametinib run-in followed by concurrent pembrolizumab every 3 weeks (Q3W) plus trametinib once daily (QD). Intermittent dosing was 2 weeks of trametinib run-in followed by pembrolizumab plus intermittent trametinib (1 week off/2 weeks on). A 3 + 3 dose escalation was used, followed by dose confirmation. RESULTS Forty-two patients were enrolled. No dose-limiting toxicities (DLTs) occurred at initial dose levels (DL). At subsequent DLs, 10 of 38 evaluable patients had DLTs. For concurrent dosing, MTD was pembrolizumab 200 mg Q3W plus trametinib 1.5 mg QD, with a 2-week trametinib 1.5 mg QD run-in (concurrent DL2a); in concurrent DL2a group, five (31%) patients had grade 3/4 treatment-related adverse events (TRAEs); the objective response rate (ORR) was 0%. ORR was 40% in concurrent DL1 and 0% in concurrent DL2b. For intermittent dosing, MTD was pembrolizumab 200 mg Q3W plus trametinib 2 mg QD with a 2-week trametinib 2 mg QD run-in (intermittent DL2); in the intermittent DL2 group, seven (47%) patients had grade 3/4 TRAEs; ORR was 27%. ORR in intermittent DL1 was 33%. CONCLUSIONS MTDs for concurrent and intermittent dosing of pembrolizumab with trametinib were identified. The combination had limited antitumour activity, numerically higher ORR with intermittent versus concurrent dosing, and manageable safety. CLINICALTRIALS. GOV IDENTIFIER NCT02130466.

PURPOSE The combination of talimogene laherparepvec (T-VEC) and pembrolizumab previously demonstrated an acceptable safety profile and an encouraging complete response rate (CRR) in patients with advanced melanoma in a phase Ib study. We report the efficacy and safety from a phase III, randomized, double-blind, multicenter, international study of T-VEC plus pembrolizumab (T-VEC-pembrolizumab) versus placebo plus pembrolizumab (placebo-pembrolizumab) in patients with advanced melanoma. METHODS Patients with stage IIIB-IVM1c unresectable melanoma, naïve to antiprogrammed cell death protein-1, were randomly assigned 1:1 to T-VEC-pembrolizumab or placebo-pembrolizumab. T-VEC was administered at ≤ 4 × 106 plaque-forming unit (PFU) followed by ≤ 4 × 108 PFU 3 weeks later and once every 2 weeks until dose 5 and once every 3 weeks thereafter. Pembrolizumab was administered intravenously 200 mg once every 3 weeks. The dual primary end points were progression-free survival (PFS) per modified RECIST 1.1 by blinded independent central review and overall survival (OS). Secondary end points included objective response rate per mRECIST, CRR, and safety. Here, we report the primary analysis for PFS, the second preplanned interim analysis for OS, and the final analysis. RESULTS Overall, 692 patients were randomly assigned (346 T-VEC-pembrolizumab and 346 placebo-pembrolizumab). T-VEC-pembrolizumab did not significantly improve PFS (hazard ratio, 0.86; 95% CI, 0.71 to 1.04; P = .13) or OS (hazard ratio, 0.96; 95% CI, 0.76 to 1.22; P = .74) compared with placebo-pembrolizumab. The objective response rate was 48.6% for T-VEC-pembrolizumab (CRR 17.9%) and 41.3% for placebo-pembrolizumab (CRR 11.6%); the durable response rate was 42.2% and 34.1% for the arms, respectively. Grade ≥ 3 treatment-related adverse events occurred in 20.7% of patients in the T-VEC-pembrolizumab arm and in 19.5% of patients in the placebo-pembrolizumab arm. CONCLUSION T-VEC-pembrolizumab did not significantly improve PFS or OS compared with placebo-pembrolizumab. Safety results of the T-VEC-pembrolizumab combination were consistent with the safety profiles of each agent alone.

Melanoma can frequently metastasize to the brain with severe consequences. However, variation of melanoma brain metastases (MBM) development among populations is not well studied, and underlying mechanisms and risk factors for MBM development are not consistently documented. We conducted a systematic literature review (SLR) including a total of 39 articles to evaluate the proportion of melanoma patients who are diagnosed with, or develop, brain metastases, and summarize the risk factors of MBM. The average proportion of MBM was calculated and weighted by the sample size of each study. Meta-analyses were conducted for the selected risk factors using a random-effects model. The proportion of MBM at diagnosis was 33% (975 with MBM out of 2948 patients) among patients with cutaneous melanoma (excluding acral) and 23% (651/2875) among patients with cutaneous mixed with other types of melanoma. The proportion at diagnosis was lower among populations with mucosal (9/96, 9%) or uveal (4/184, 2%) melanoma and among populations outside the United States and Europe. Meta-analysis demonstrated that male vs. female gender and left-sided tumors vs. right-sided were significantly associated with increased risk of melanoma brain metastases. These data may help clinicians to assess an individual patient’s risk of developing melanoma brain metastases.

BackgroundUp to 60% of melanoma patients develop melanoma brain metastases (MBM), which traditionally have a poor diagnosis. Current treatment strategies include immunotherapies (IO), targeted therapies (TT), and stereotactic radiosurgery (SRS), but there is considerable heterogeneity across worldwide consensus guidelines.ObjectiveTo summarize current treatments and compare worldwide guidelines for the treatment of MBM.MethodsReview of global consensus treatment guidelines for MBM patients.ResultsSubstantial evidence supported that concurrent IO or TT plus SRS improves progression-free survival (PFS) and overall survival (OS). Guidelines are inconsistent with regards to recommendations for surgical resection of MBM, since surgical resection of symptomatic lesions alleviates neurological symptoms but does not improve OS. Whole-brain radiation therapy is not recommended by all guidelines due to negative effects on neurocognition but can be offered in rare palliative scenarios.ConclusionWorldwide consensus guidelines consistently recommend up-front combination IO or TT with or without SRS for the treatment of MBM.

BACKGROUND: Pembrolizumab shows robust antitumor activity and favorable safety in metastatic melanoma. KEYNOTE-151 evaluated pembrolizumab in Chinese patients, who have more aggressive melanoma subtypes than other populations. METHODS: Chinese patients aged ≥18 years with advanced melanoma previously treated with one line of therapy received pembrolizumab 2 mg/kg every 3 weeks for 35 cycles or until confirmed disease progression, intolerable toxicity, or study withdrawal. Primary end points were objective response rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 by blinded independent central review and safety. Key secondary end points included duration of response (DOR) and progression-free survival (PFS) per RECIST v1.1 and overall survival (OS). RESULTS: Median age was 52 years (N = 103); 37.9% had acral and 14.6% had mucosal melanoma. Median follow-up was 7.9 months at data cutoff (December 27, 2017). ORR was 16.7% [95% confidence internal (CI), 10.0%-25.3%] (1 complete, 16 partial responses). Disease control rate was 38.2%. ORR was 15.8% for acral and 13.3% for mucosal melanoma. Median DOR was 8.4 months; 65.6% of patients had response duration ≥6 months. Median PFS was 2.8 months (95% CI, 2.7-3.5 months); 6-month rate was 20.4%. Median OS was 12.1 months (95% CI, 9.6 months–not reached); 6-month rate, 75.7%; and 12-month rate, 50.6%. Treatment-related AEs (TRAEs) occurred in 87 (84.5%) patients; 9 (8.7%) experienced grade 3/4 TRAE and 2 (1.9%) discontinued because of TRAE; none died. Two deaths occurred that were unrelated to treatment. CONCLUSIONS: Pembrolizumab was well tolerated and provided clinically meaningful antitumor activity as second-line therapy in Chinese patients with advanced melanoma.

TPS9589 Background: The treatment of melanoma has improved markedly with the emergence of new immune therapies, and both anti-PD-1 monotherapy and the combination of the anti-PD-1 antibody nivolumab and anti-CTLA-4 therapy ipilimumab are now considered standard-of-care in the unresectable or metastatic (advanced) melanoma setting. However, many patients have primary or acquired resistance to these therapies, thereby underpinning the need for more effective approaches. IO102-IO103 is a potentially first-in-class, dual-antigen, immune-modulatory therapy targeting the key cancer immune resistance pathways mediated by IDO and PD-L1. The ability of IO102 and IO103 to respectively activate the specific T cells that recognize these checkpoint molecules and directly modulate immune regulation has previously been demonstrated both preclinically and in human clinical trials. A synergistic anti-tumor response upon treatment against both IDO and PD-L1 has also previously been demonstrated in a preclinical model where IDO and PD-L1 were expressed by different cells in the tumor microenvironment. Due to the distinctive mechanisms of action of IO102-IO103 and anti-PD-1 antibodies, there may be a further synergistic effect when treatment is combined. A previous Phase 1/2 trial investigating the use of IO102-IO103 plus nivolumab in patients with anti-PD-1-naïve metastatic melanoma has demonstrated promising anti-tumor activity with an overall response rate (ORR) of 80%, median progression-free survival (PFS) of 26 months and a manageable safety profile (NCT03047928; Kjeldsen et al, Nat Med 2021). Methods: This is a Phase 3, multicenter, open-label, randomized, 2-arm trial investigating the efficacy and safety of IO102-IO103 plus pembrolizumab versus pembrolizumab alone (EudraCT: 2021-004594-32; ClinicalTrials.gov No: NCT05155254). Inclusion criteria include: adult patients with untreated, unresectable (Stage III), or metastatic (Stage IV) melanoma; > 6 months since last dose of (neo)adjuvant treatment with targeted or immune therapy (in those previously treated); and ≥1 measurable lesion by RECIST v1.1. Primary endpoint is PFS by blinded independent central review. Secondary endpoints include ORR, durable response rate, complete response rate, duration of response, time to response, disease control rate, overall survival, and safety/tolerability. Target enrollment is 300 patients at > 100 sites in 20 countries. Patients are randomized 1:1 to receive either pembrolizumab 200 mg intravenously (IV) every 3 weeks up to 2 years or pembrolizumab 200 mg IV every 3 weeks up to 2 years with dual-antigen IO103-IO102 85-85 µg and Montanide adjuvant subcutaneously on Day 1 and 8 of cycle 1 and 2 and on Day 1 of each cycle thereafter. Enrolment for the study is ongoing. Clinical trial information: EudraCT: 2021-004594-32; ClinicalTrials.gov No: NCT05155254.

Objective Patients with melanoma and early stable disease (SD) with pembrolizumab have unclear prognosis. We present post hoc analyses of long-term outcomes for patients with early SD, partial response (PR) or complete response (CR) with pembrolizumab. Patients and methods Patients who received pembrolizumab in the KEYNOTE-001 and KEYNOTE-006 studies and had SD, PR or CR at weeks 12 or 24 were included. Results Of 294 patients in the week 12 analysis, 107 (36.4%) had SD at week 12, of whom 7 (6.5%) had a best overall response of CR, 43 (40.2%) had PR and 57 (53.3%) had SD. Forty-eight–month overall survival (OS) rates were 95.2%, 73.0% and 47.7%, respectively, for patients with CR, PR and SD at week 12. Similar results were observed in the 241 patients in the week 24 analysis. Forty-eight–month OS rates were 72.1% for patients with SD at week 12 followed by subsequent response and 75.0% for patients with PR at week 12 followed by no change in response or progression. Thirty-six–month and 48-month OS rates were 11.6% and not reached, respectively, for patients with SD at week 12 followed by progression before week 24. Conclusions A substantial proportion of patients (46.7%) with early (week 12) SD with pembrolizumab achieved subsequent PR or CR. Patients with SD at week 12 and subsequent CR/PR had similar survival to those who maintained PR. In contrast, patients with SD at week 12 and subsequent progression had poor survival outcomes. These findings may guide treatment decisions for patients achieving early SD. Trial registration Clinicaltrials.gov : NCT01295827 (KEYNOTE-001); NCT01866319 (KEYNOTE-006).

ObjectiveLong-term safety of pembrolizumab in melanoma was analyzed in KEYNOTE-001, KEYNOTE-002, and KEYNOTE-006.Patients and methodsAnalysis involved patients who received ≥1 pembrolizumab dose. Lead-time bias was addressed via landmark analyses in patients who were progression-free before day 147.ResultsAdverse events (AEs) were analyzed for 1567 patients (median follow-up, 42.4 months). Most AEs were mild/moderate; grade 3/4 treatment-related AEs occurred in 17.7% of patients. Two pembrolizumab-related deaths occurred. Any-grade immune-mediated AEs (imAEs) occurred in 23.0%, most commonly hypothyroidism (9.1%), pneumonitis (3.3%), and hyperthyroidism (3.0%); grade 3/4 imAEs occurred in 6.9% of patients. Most imAEs occurred within 16 weeks of treatment. In landmark analysis, patients who did (n=79) versus did not (n=384) develop imAEs had similar objective response rates (ORRs) (64.6% versus 63.0%); median time to response (TTR), 5.6 months for both; median duration of response (DOR), 20.0 versus 25.3 months; median progression-free survival (PFS), 17.0 versus 17.7 months; median overall survival (OS), not reached (NR) versus 43 months (p=0.1104). Patients who did (n=17) versus did not (n=62) receive systemic corticosteroids had similar ORRs (70.6% vs. 62.9%) and median TTR (6.4 vs. 5.6 months) but numerically shorter median PFS (9.9 vs. 17.0 months); median DOR, 14.2 months versus NR; median OS, NR for both.ConclusionsThese results enhance the knowledge base for pembrolizumab in advanced melanoma, with no new toxicity signals after lengthy follow-up of a large population. In landmark analyses, pembrolizumab efficacy was similar regardless of imAEs or systemic corticosteroid use.Clinical trial registryNCT01295827, NCT01704287, NCT01866319.

Author(s): Ferrucci, Pier Francesco; Di Giacomo, Anna Maria; Del Vecchio, Michele; Atkinson, Victoria; Schmidt, Henrik; Schachter, Jacob; Queirolo, Paola; Long, Georgina V; Stephens, Rosalie; Svane, Inge Marie; Lotem, Michal; Abu-Amna, Mahmoud; Gasal, Eduard; Ghori, Razi; Diede, Scott J; Croydon, Elizabeth S; Ribas, Antoni; Ascierto, Paolo Antonio; KEYNOTE-022 international team | Abstract: BackgroundIn the KEYNOTE-022 study, pembrolizumab with dabrafenib and trametinib (triplet) improved progression-free survival (PFS) versus placebo with dabrafenib and trametinib (doublet) without reaching statistical significance. Mature results on PFS, duration of response (DOR), and overall survival (OS) are reported.MethodsThe double-blind, phase 2 part of KEYNOTE-022 enrolled patients with previously untreated BRAF V600E/K-mutated advanced melanoma from 22 sites in seven countries. Patients were randomly assigned 1:1 to intravenous pembrolizumab (200 mg every 3 weeks) or placebo plus dabrafenib (150 mg orally two times per day) and trametinib (2 mg orally one time a day). Primary endpoint was PFS. Secondary endpoints were objective response rate, DOR, and OS. Efficacy was assessed in the intention-to-treat population, and safety was assessed in all patients who received at least one dose of study drug. This analysis was not specified in the protocol.ResultsBetween November 30, 2015 and April 24, 2017, 120 patients were randomly assigned to triplet (n=60) or doublet (n=60) therapy. With 36.6 months of follow-up, median PFS was 16.9 months (95% CI 11.3 to 27.9) with triplet and 10.7 months (95% CI 7.2 to 16.8) with doublet (HR 0.53; 95% CI 0.34 to 0.83). With triplet and doublet, respectively, PFS at 24 months was 41.0% (95% CI 27.4% to 54.2%) and 16.3% (95% CI 8.1% to 27.1%); median DOR was 25.1 months (95% CI 14.1 to not reached) and 12.1 months (95% CI 6.0 to 15.7), respectively. Median OS was not reached with triplet and was 26.3 months with doublet (HR 0.64; 95% CI 0.38 to 1.06). With triplet and doublet, respectively, OS at 24 months was 63.0% (95% CI 49.4% to 73.9%) and 51.7% (95% CI 38.4% to 63.4%). Grade 3-5 treatment-related adverse events (TRAEs) occurred in 35 patients (58%, including one death) receiving triplet and 15 patients (25%) receiving doublet.ConclusionIn BRAF V600E/K-mutant advanced melanoma, pembrolizumab plus dabrafenib and trametinib substantially improved PFS, DOR, and OS with a higher incidence of TRAEs. Interpretation of these results is limited by the post hoc nature of the analysis.

10013 Background: 5-year follow-up of the phase 3 KEYNOTE-006 study (NCT01866319) showed pembro improved OS vs ipilimumab (ipi) in patients (pts) with advanced melanoma. 3-y OS rate from pembro completion for pts who completed 2 y of pembro was 93.8%. Results with 8 mo of additional follow-up are presented to inform clinical care. Methods: Eligible pts with ipi-naive advanced melanoma, ≤1 prior therapy for BRAF-mutant disease, and ECOG PS 0 or 1 were randomized to pembro 10 mg/kg Q2W or Q3W for ≤2 y or ipi 3 mg/kg Q3W for 4 doses. Pts discontinuing pembro with CR, PR, or SD after ≥94 weeks were considered pts with 2-y pembro. Pts who stopped pembro with SD, PR or CR could receive ≤12 mo of additional pembro (2nd course) upon disease progression if still eligible. ORR was assessed per immune-related response criteria by investigator review. OS was estimated using the Kaplan-Meier method. Pembro arm data were pooled. Post hoc ITT efficacy analyses are shown. Results: Median follow-up from randomization to data cutoff (Jul 31, 2019) was 66.7 mo in the pembro and 66.9 mo in the ipi arms. OS outcomes are shown in Table. For the 103 pts with 2-y pembro (30 CR, 63 PR, 10 SD), median follow-up from completion was 42.9 mo (95% CI, 39.9-46.3).Median DOR was not reached. 36-mo OS from pembro completion was 100% (95% CI, 100.0-100.0) for pts with CR, 94.8% (95% CI, 84.7-98.3) for pts with PR, and 66.7% (95% CI, 28.2-87.8) for pts with SD. 15 pts received 2nd-course pembro; BOR in 1st course was 6 CR, 6 PR, and 3 SD. Median time from end of 1st course to start of 2ndcourse was 24.5 mo (range, 4.9-41.4). Median follow-up in pts who received 2nd-course pembro was 25.3 mo (range, 3.5-39.4). Median duration of 2nd-course pembro was 8.3 mo (range, 1.4-12.6). BOR on 2ndcourse was 3 CR, 5 PR (ongoing responses, 7 pts), 3 SD (ongoing, 2 pts), and 2 PD (1 death); 2 pts pending. Conclusions: Pembro improves the long-term survival vs ipi in pts with advanced melanoma, with all pts who completed therapy in CR still alive at 5 years. Retreatment with pembro at progression in pts who stopped at SD or better can provide additional clinical benefit in a majority of pts. Clinical trial information: NCT01866319. [Table: see text]

The third multistakeholder Paediatric Strategy Forum organised by ACCELERATE and the European Medicines Agency focused on immune checkpoint inhibitors for use in combination therapy in children and adolescents. As immune checkpoint inhibitors, both as monotherapy and in combinations have shown impressive success in some adult malignancies and early phase trials in children of single agent checkpoint inhibitors have now been completed, it seemed an appropriate time to consider opportunities for paediatric studies of checkpoint inhibitors used in combination. Among paediatric patients, early clinical studies of checkpoint inhibitors used as monotherapy have demonstrated a high rate of activity, including complete responses, in Hodgkin lymphoma and hypermutant paediatric tumours. Activity has been very limited, however, in more common malignancies of childhood and adolescence. Furthermore, apart from tumour mutational burden, no other predictive biomarker for monotherapy activity in paediatric tumours has been identified. Based on these observations, there is collective agreement that there is no scientific rationale for children to be enrolled in new monotherapy trials of additional checkpoint inhibitors with the same mechanism of action of agents already studied (e.g. anti-PD1, anti-PDL1 anti-CTLA-4) unless additional scientific knowledge supporting a different approach becomes available. This shared perspective, based on scientific evidence and supported by paediatric oncology cooperative groups, should inform companies on whether a paediatric development plan is justified. This could then be proposed to regulators through the available regulatory tools. Generally, an academic-industry consensus on the scientific merits of a proposal before submission of a paediatric investigational plan would be of great benefit to determine which studies have the highest probability of generating new insights. There is already a rationale for the evaluation of combinations of checkpoint inhibitors with other agents in paediatric Hodgkin lymphoma and hypermutated tumours in view of the activity shown as single agents. In paediatric tumours where no single agent activity has been observed in multiple clinical trials of anti-PD1, anti-PDL1 and anti-CTLA-4 agents as monotherapy, combinations of checkpoint inhibitors with other treatment modalities should be explored when a scientific rationale indicates that they could be efficacious in paediatric cancers and not because these combinations are being evaluated in adults. Immunotherapy in the form of engineered proteins (e.g. monoclonal antibodies and T cell engaging agents) and cellular products (e.g. CAR T cells) has great therapeutic potential for benefit in paediatric cancer. The major challenge for developing checkpoint inhibitors for paediatric cancers is the lack of neoantigens (based on mutations) and corresponding antigen-specific T cells. Progress critically depends on understanding the immune macroenvironment and microenvironment and the ability of the adaptive immune system to recognise paediatric cancers in the absence of high neoantigen burden. Future clinical studies of checkpoint inhibitors in children need to build upon strong biological hypotheses that take into account the distinctive immunobiology of childhood cancers in comparison to that of checkpoint inhibitor responsive adult cancers. (C) 2020 The Authors. Published by Elsevier Ltd.

Purpose Pembrolizumab provides durable antitumor activity in metastatic melanoma, including complete response (CR) in about 15% of patients. Data are limited on potential predictors of CR and patient disposition after pembrolizumab discontinuation after CR. We describe baseline characteristics and long-term follow-up in patients who experienced CR with pembrolizumab in the KEYNOTE-001 study ( ClinicalTrials.gov identifier: NCT01295827). Patients and Methods Patients with ipilimumab-naive or -treated advanced/metastatic melanoma received one of three dose regimens of pembrolizumab. Eligible patients who received pembrolizumab for ≥ 6 months and at least two treatments beyond confirmed CR could discontinue therapy. Response was assessed every 12 weeks by central Response Evaluation Criteria in Solid Tumors version 1.1. For this analysis, CR was defined per investigator assessment, immune-related response criteria, and potential predictors of CR were evaluated using univariate and multivariate analyses. Results Of 655 treated patients, 105 (16.0%) achieved CR after median follow-up of 43 months. At data cutoff, 92 patients (87.6%) had CR, with median follow-up of 30 months from first CR. Fourteen (13.3%) patients continued to receive treatment for a median of ≥ 40 months. Pembrolizumab was discontinued by 91 patients (86.7%), including 67 (63.8%) who proceeded to observation without additional anticancer therapy. The 24-month disease-free survival rate from time of CR was 90.9% in all 105 patients with CR and 89.9% in the 67 patients who discontinued pembrolizumab after CR for observation. Tumor size and programmed death-ligand 1 status were among the baseline factors independently associated with CR by univariate analysis. Conclusion Patients with metastatic melanoma can have durable complete remission after discontinuation of pembrolizumab, and the low incidence of relapse after median follow-up of approximately 2 years from discontinuation provides hope for a cure for some patients. The mechanisms underlying durable CR require further investigation.

BACKGROUND NF1-related PN can cause substantial morbidity, with no currently approved drug treatment available for PN treatment. Although surgery is the standard of care, complete resection of PN is often difficult due to encasement of vital structures and invasive and extensive PN growth. With limited real-world data among children with NF1-related PN, the study objectives were to describe the demographic, clinical characteristics, and treatment of these children. METHODS A cross-sectional analysis of existing CTF web-based, patient-entered, registry data collected between 2012–2018 was conducted. To be included in analysis, patients had to complete at least one registry survey, and be ≤ 19 years of age at the time of first survey completion, with patient- or parent/ guardian reported diagnosis of NF1 and at least 1 PN. Descriptive statistical analysis was conducted on data collected from the first survey for each patient, to describe patient characteristics and treatment patterns. Results were stratified by region (US, ex-US). RESULTS The sample included 943 pediatric patients (n=750 US, n=193 ex-US). The majority (85.9%) were less than 5 years of age at NF1 diagnosis (US: 87.6%; ex-US: 79.3%). Approximately half were male, and half reported more than 1 PN. The most common PN site include head (15.1%) and neck (12.6%). More than half of patients received no treatment (53.1%) for their PN. The most common treatments reported for PN were surgery (27.0%) and chemotherapy or drug therapy (10.0%). These results were generally consistent across regions. A malignant peripheral nerve sheath tumor (MPNST) and optic glioma (OG) were diagnosed in 21 (2.2%) and 308 (32.7%) patients, respectively; a large proportion of OG patients remained untreated (57.5%). Too few ex-US patients were available for detailed regional analysis. CONCLUSIONS This study demonstrated that a large proportion of children diagnosed with NF1-related PN remain untreated, highlighting a substantial unmet need.

e21511 Background: Pembro as 2L therapy was well tolerated and had clinically meaningful antitumor activity in Chinese pts with advanced melanoma at first analysis of the phase 1b KEYNOTE-151 study. At median FU of 7.9 mo, ORR was 16.7% (1 complete response [CR]; 16 partial response [PR]), DCR was 38.2%, median DOR was 8.4 mo, median PFS was 2.8 mo, and median OS was 12.1 mo. Any grade and grade 3/4 treatment-related adverse events (TRAEs) occurred in 84.5% and 8.7% of pts, respectively. However, long-term efficacy and safety of 2L pembro in Chinese pts with advanced melanoma are unknown. Results from 3 y of FU are presented. Methods: Eligible pts were ≥18 y, of Chinese descent, had histologically confirmed locally advanced or metastatic melanoma, and had disease progression on or after first line therapy. Pts received pembro 2 mg/kg IV Q3W for ≤35 cycles. Eligible pts who discontinued pembro with stable disease or better could receive ≤17 additional cycles of pembro (second course) upon disease progression. Primary endpoints were safety and ORR per RECIST 1.1 by blinded independent central review (BICR). Secondary endpoints included DOR and PFS per RECIST 1.1 by BICR; ORR, DOR, and PFS per irRECIST by BICR; and OS. ORR was based on the exact binomial method; DOR, PFS, and OS analyses used the Kaplan-Meier method. The full analysis set (FAS) comprised all allocated pts who received ≥1 pembro dose and had baseline data for relevant analyses. Results: Of 103 enrolled pts, 43% were male, 51% had PD-L1 positive tumors, and 80% had BRAF wild-type tumors; median age was 52 y (range, 22-77). The FAS had 102 pts. Median time from first dose to database cutoff was 44.6 mo (IQR, 39.1-46.2). At database cutoff (July 13, 2020), 14 pts (13.5%) had completed treatment, 89 pts (86.4%) had discontinued. Any grade TRAEs occurred in 88 pts (85.4%); most commonly hypothyroidism (n = 27; 26.2%), increased ALT (n = 24; 23.3%), and hypertriglyceridemia (n = 23; 22.3%), all grade 1/2. Grade 3-5 TRAEs occurred in 13 pts (12.6%). Immune-mediated AEs and infusion reactions occurred in 35 pts (34.0%); most commonly grade 1/2 hypothyroidism (n = 27; 26.2%). 3 pts discontinued pembro because of a TRAE; none died because of a TRAE. ORR per RECIST 1.1 was 17.6% (95% CI 10.8-26.4; 1 CR/17 PR); DCR was 38.2% (95% CI 28.8-48.4). Median DOR per RECIST 1.1 was 13.8 mo (range, 2.7-37.4+); 1 pt had response duration ≥36 mo. Median PFS per RECIST 1.1 was 2.8 mo (95% CI 2.7-3.5); 36-mo PFS rate was 5.0%. ORR, DOR, and PFS were similar per RECIST 1.1 and irRECIST. Median OS was 13.2 mo (95% CI 10.4-16.5); 36-mo OS rate, 22.3%.1 pt completed the first and second courses of pembro and had investigator-confirmed CR. Conclusions: 2L pembro was well tolerated and continued to provide durable responses and clinically meaningful antitumor activity in Chinese pts with advanced melanoma. These results further support use of 2L pembro in Chinese pts with advanced melanoma. Clinical trial information: NCT02821000.

9504 Background: Initial results of the open-label, single-arm, phase 2 LEAP-004 study (NCT03776136) showed that len and pembro in combination had promising efficacy and manageable safety in pts with unresectable stage III-IV melanoma and confirmed PD on a PD-(L)1 inhibitor given alone or in combination. ORR was 21.4% with a 6.3-mo median DOR; ORR was 31.0% in patients with PD on prior anti–PD-1 + anti–CTLA-4. We present updated data from LEAP-004 and additional ORR subgroup analyses. Methods: Eligible pts with PD confirmed per iRECIST within 12 wk of the last dose of a PD-(L)1 inhibitor given alone or with anti–CTLA-4 or other therapies for ≥2 doses received len 20 mg/d once daily plus ≤35 doses of pembro 200 mg Q3W until PD or unacceptable toxicity. Primary end point is ORR per RECIST v1.1 by blinded independent central review (BICR). Secondary end points are PFS and DOR per RECIST v1.1 by BICR, OS, and safety. ORR was calculated for pts with PD on prior anti–PD-1 + anti–CTLA-4, pts whose only prior anti–PD-(L)1 was in the adjuvant setting, pts with primary resistance (ie, best response of SD or PD to prior anti–PD-(L)1 in the advanced setting) and pts with secondary resistance (ie, PD following best response of CR or PR on prior anti–PD-(L)1 in the advanced setting). Results: 103 pts were enrolled. Median age was 63 y, 68.0% of pts had stage M1c/M1d disease, 55.3% had LDH > ULN (20.4% ≥2 × ULN), 58.3% received ≥2 prior treatments, 94.2% received therapy for advanced disease, and 32.0% received BRAF ± MEK inhibition. With median study follow-up of 15.3 mo (range 12.1-19.0), 17.5% of pts were still receiving study drug. ORR by BICR remained 21.4% (95% CI 13.9-30.5), although the number of CRs increased from 2 to 3. DCR was 66.0%. Median DOR increased to 8.2 mo, and the KM estimate of DOR ≥9 mo was 37.2%. ORR was 33.3% in pts with PD on prior anti–PD-1 + anti–CTLA-4 (n = 30), 18.2% in pts whose only prior anti–PD-1/L1 was in the adjuvant setting (n = 11), 22.6% in pts with primary resistance (n = 62), and 22.7% in pts with secondary resistance (n = 22). Median (95% CI) PFS and OS in the total population were 4.2 mo (3.8-7.1) and 14.0 mo (95% CI 10.8-NR); 12-mo PFS and OS estimates were 17.8% and 54.5%. Incidence of treatment-related AEs was as follows: 96.1% any grade, 45.6% grade 3-4, 1.0% grade 5 (decreased platelet count), 7.8% led to discontinuation of len and/or pembro, and 56.3% led to len dose reduction. Conclusions: The combination of len and pembro continues to show clinically meaningful, durable responses in pts with advanced MEL with confirmed progression on a prior PD-(L)1 inhibitor, including those with PD on anti–PD-1 + anti–CTLA-4 therapy, and regardless of primary or secondary resistance to prior anti–PD-(L)1 therapy. The safety profile was consistent with prior studies of len + pembro. These data support len + pembro as a potential regimen for this population of high unmet need. Clinical trial information: NCT03776136.

Here we report a phase 1b clinical trial testing the impact of oncolytic virotherapy with talimogene laherparepvec on cytotoxic Tcell infiltration and therapeutic efficacy of the anti-PD-1 antibody pembrolizumab. Twenty-one patients with advanced melanoma were treated with talimogene laherparepvec followed by combination therapy with pembrolizumab. Therapy was generally well tolerated, with fatigue, fevers, and chills as the most common adverse events. No dose-limiting toxicities occurred. Confirmed objective response rate was 62%, with a complete response rate of 33% per immune-related response criteria. Patients who responded to combination therapy had increased CD8+ Tcells, elevated PD-L1 protein expression, as well as IFN-γ gene expression on several cell subsets in tumors after talimogene laherparepvec treatment. Response tocombination therapy did not appear to be associated with baseline CD8+ Tcell infiltration or baseline IFN-γ signature. These findings suggest that oncolytic virotherapy may improve the efficacy of anti-PD-1 therapy by changing the tumor microenvironment. VIDEO ABSTRACT.

Introduction: Pembro significantly improved OS vs ipi in advanced melanoma in the KEYNOTE-006 study (NCT01866319). We present outcomes from the 5-year follow-up of this study−the longest to date in a randomized phase 3 trial of pembro in advanced cancer. Long-term follow-up for pts completing 2 years of pembro and data for pts treated with a second course (2nd course) of pembro are also reported. Methods: Eligible pts (N=834) were randomly assigned (1:1:1) to pembro 10 mg/kg Q2W or Q3W for up to 2 years or ipi 3 mg/kg Q3W for 4 doses. Eligible pts who completed pembro or stopped for CR and then progressed could receive an additional 12 mo of pembro if they met inclusion criteria. End points included OS and ORR per irRC by investigator review. Pembro completion was defined as discontinuation with CR, PR, or SD after ≥94 weeks of pembro. Results were pooled from the 2 pembro arms. Results: At data cutoff (Dec 3, 2018), median follow-up of surviving pts was 57.7 mo (range, 0.03-62.1). Median OS (95% CI) was 32.7 mo (24.5-41.6) in the combined pembro arms (n=556) and 15.9 mo (13.3-22.0) in the ipi arm (n=278) (HR, 0.73). Five-year OS rates (95% CI) were estimated to be 38.7% (34.2-43.1) and 31.0% (25.3-36.9), respectively. For pts receiving first-line pembro, median OS (95% CI) was 38.7 mo (27.3-50.7) in the combined pembro arms (n=368) and 17.1 mo (13.8-26.2) in the ipi arm (n=181) (HR, 0.73); 5-year OS rates (95% CI) were estimated to be 43.2% (38.0-48.3) and 33.0% (25.8-40.3), respectively. A total of 103 (18.5%) pts completed 2 years of pembro; median survival follow-up from pembro completion was 34.5 mo; OS rate at 36 mo was 93.8%. Of the 103 pts, 76 were progression-free and 27 had PD. Median time from pembro end to progression was 16.8 mo (range, 0.99-33.9). Thirteen pts received 2nd course pembro; best overall response (BOR) in 1st course was 6 CR, 6 PR, and 1 SD. Median duration of 2nd-course pembro was 9.7 mo; BOR on 2nd course was 3 CR, 4 PR, 3 SD, and 1 PD (response assessment was pending for 2 pts). All 3 pts with 2nd-course CR and 2 of 4 with PR had ongoing response; the remaining 2 pts who had 2nd-course PR subsequently progressed. Four pts discontinued 2nd-course treatment before 12 mo (2 due to PD, 1 due to G2 interstitial pneumonia, and 1 due to physician decision). Six pts had grade1/2 TRAEs during 2nd-course pembro; there were no grade 3/4 TRAEs or deaths. Conclusions: Pembro continued to show improved OS vs ipi in 5-year follow-up of pts with advanced melanoma with 43.2% estimated to be alive at 5 years versus 33.0% with ipi. Almost one-fifth of pts completed 2 years of pembro, and 93.8% are estimated to be alive 3 years after pembro completion. Second-course pembro treatment was generally well tolerated and provided additional antitumor activity. These results confirm that 2-year pembro is an effective treatment for pts with advanced melanoma. Citation Format: Caroline Robert, Jacob Schachter, Georgina V. Long, Ana Arance, Jean-Jacques Grob, Laurent Mortier, Adil Daud, Matteo S. Carlino, Catriona McNeil, Michal Lotem, James Larkin, Paul Lorigan, Bart Neyns, Christian U. Blank, Omid Hamid, Teresa M. Petrella, James Anderson, Clemens Krepler, Scott J. Diede, Antoni Ribas. 5-year survival and other long-term outcomes from KEYNOTE-006 study of pembrolizumab (pembro) for ipilimumab (ipi)-naive advanced melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT188.

9532 Background: Both pembrolizumab (PEMBRO) and combination ipilimumab + nivolumab (IPI+NIVO) are FDA-approved immunotherapies for advanced melanoma (AM). These two treatment regimens have different toxicity profiles which may impact health care resource utilization (HCRU). Our aim was to compare real-world risk of hospitalization and emergency department (ED) visits within 12 months of starting the two treatment regimens. Methods: A retrospective cohort study was conducted in patients ≥18 years old with AM initiating PEMBRO or IPI+NIVO between Jan 1, 2016 – Dec 30, 2017. Patients were identified from 12 US academic medical centers and affiliated satellite clinics. Data were abstracted through chart review. All-cause hospitalizations or ED visits and the rates per patient per month (PPPM) through 12 months of follow-up were calculated. Utilization was compared between PEMRBO and IPI+NIVO using multivariate logistic regression analysis. Results: 400 patients were included, 200 each PEMBRO and IPI+NIVO with mean (SD) follow-up time of 10 (3) and 10 (4) months, respectively. The PEMBRO cohort had poorer Eastern Cooperative Group (ECOG) performance status at treatment start, 71% ECOG 0 or 1 vs 88% (p < .001); more diabetes, 21% vs 13% (p = .045); a trend towards more heart disease, 18% vs 12% (p = .067); were more likely to be PD-L1 expression positive, 77% vs 63% (p = .011); and less likely to harbor a BRAF mutation, 35% vs 50% (p = .003). The proportion with at least one hospitalization through 12 months was 17% PEMBRO vs 24% IPI+NIVO. Less than 2% of patients had more than one admission and none had more than two, regardless of cohort. Unadjusted mean (SD) PPPM hospitalizations were .016 (.037) for PEMBRO and .020 (.038) for IPI+NIVO. The adjusted odds ratio for any hospitalization with PEMBRO was 0.55 (95% CI .31, .97; p = .039) vs. IPI+NIVO. ED visits occurred in 18% vs 21% in PEMBRO and IPI+NIVO respectively, with no difference in covariate-adjusted analysis (p = .147). Conclusions: Patients receiving PEMBRO had a significantly lower probability of hospitalization and similar probability of ER visits compared with IPI+NIVO in the real world through 12 months.

e21031 Background: Pembrolizumab (PEM), a humanized antibody targeting programmed death-1 receptor, has been approved by FDA for the treatment of patients (pts) with advanced melanoma (AM) in the US since 2014. Real-world (RW) data supports the clinical effectiveness of 1L use of PEM, but there is limited information of PEM later line use. The study examined the RW outcomes of pts treated with PEM who have failed prior lines of therapy in US oncology clinical practices. Methods: Flatiron Health longitudinal database was used to identify adult pts with AM who received ≥1 dose of PEM in second line (2L) or later (3L+) between September 4, 2014 and May 31, 2017. Pts were followed up to May 31, 2018. Pts in clinical trials were excluded. Pt demographic, treatment, and clinical characteristics were described. Time on treatment (ToT) and overall survival (OS) were analyzed using the Kaplan Meier (KM) method, with the first dose of PEM as the starting point. Results: Two hundred thirty-six pts were included in the analysis, of which there were 171 2L and 65 3L+. Overall, median age at PEM initiation was 66 years; most were male (66.1%) and Caucasian (95.4%). 41.1% of pts’ tumors were confirmed BRAF mutant; 49.6% of pts’ tumors were confirmed BRAF wildtype; the rest was not tested or indeterminate. When data were available, 26.2% had an elevated lactate dehydrogenase (> ULN), 24.6% had brain metastases, and 25.5% had an ECOG performance status of > 1. At the time of analysis, pts were followed for a median of 12.5 months (mo, range, 0.1-44.6). Overall median ToT was 4.4 mo (95% CI, 3.5-5.3), with 4.7 and 4.4 mo in 2L and 3L+, respectively. Overall median OS was 16.8 mo (95% CI, 12.2-25.9), with 16.8 and 18.9 mo for 2L and 3L+ respectively. 1-year and 2-year survival, using the KM method, was 58.0% (95% CI, 51.2-64.1; 2L, 57.4%; 3L+, 59.6%) and 44.7% (95% CI, 37.9-51.3; 2L, 44.3%; 3L+, 46.1%) respectively. Conclusions: The study reports RW use of PEM in a large cohort of pts with AM who have failed initial therapy in US oncology clinical practices, with a heterogeneous study population compared to clinical trials. The findings of OS based on RW use suggest PEM is an effective treatment option for patients in later lines of therapy.

TPS9594 Background: Pembro, a PD-1 inhibitor, has shown effective antitumor activity, deep and durable responses, and survival benefit in treatment-naive pts and those with previously treated metastatic melanoma. Len, a potent inhibitor of VEGF receptors 1-3, FGF receptors 1-4, PDGF receptor α, RET, and KIT, combined with a PD-1 inhibitor showed antitumor activity superior to either agent alone in preclinical models of colorectal and lung cancer. Additionally, len plus pembro showed anti-tumor activity and was well-tolerated (24-wk ORR, 47.6%; TRAE: gr 3/4, 67%; gr 5, 0%) in pts with advanced melanoma previously treated with 0-2 therapies in the phase 1b/2 KEYNOTE-146 trial. The efficacy and safety of len plus pembro combination therapy will be evaluated in an open-label, phase 2 trial of pts with advanced melanoma that progressed on PD-1/PD-L1 inhibitor therapy (NCT03776136). Methods: Key inclusion criteria: age ≥18 years, histologically/cytologically confirmed unresectable stage III-IV melanoma that progressed (per iRECIST) within 12 weeks of last dose of an approved PD-1/PD-L1 inhibitor therapy (≥2 doses as monotherapy or combined with other therapies), measurable disease, ECOG PS 0/1, no active autoimmune disease, and adequate organ function. Pts must provide a baseline tumor sample. Pts will receive len 20 mg/day orally plus pembro 200 mg IV Q3W for approximately 2 years (35 doses of pembro), after which they may receive len alone until PD or unacceptable toxicity. Response will be assessed per RECIST v1.1 based on blinded independent central review (BICR) Q9W until week 54, Q12W until week 102, and Q24W thereafter. Pts with CR may discontinue treatment after ≥24 weeks of therapy; eligible pts may continue treatment beyond initial RECIST- or iRECIST-defined PD. AEs will be assessed throughout treatment and for 90 days (120 days for serious AEs) after last dose and graded per NCI CTCAE v4.0. Pts will be followed-up for survival status Q12W. The primary efficacy end point is ORR per modified RECIST v1.1 (BICR). Key secondary end points are PFS and DOR per modified RECIST v1.1 (BICR), OS, and safety; an exploratory biomarker analysis is planned. Clinical trial information: NCT03776136.

e21004 Background: Pembrolizumab (PEMBRO) and combination ipilimumab + nivolumab (IPI+NIVO) are FDA-approved immunotherapies for advanced melanoma (AM). HRQoL was better maintained with PEMBRO vs IPI in KEYNOTE-006. CheckMate-067 reported no clinically meaningful HRQoL differences with IPI+NIVO vs IPI. As randomized trial data are lacking, we compared HRQoL outcomes in AM between PEMBRO and IPI+NIVO in real-world clinical settings. Methods: A prospective, observational study was conducted with sponsor blinded to sites, and sites blinded to sponsor; nine oncologists from 9 US academic centers and affiliated satellite clinics enrolled AM patients (pts) age ≥18 years initiating first-line PEMBRO or IPI+NIVO between June 2017 – March 2018. The European Organization for the Treatment of Cancer Quality of Life Questionnaire Core-30 (EORTC QLQ C30) and EQ-5D-5L were administered at baseline and weeks 6, 12, 18, and 24 following therapy. Least squared (LS) mean changes in HRQoL scores from baseline were compared using mixed-effects models for repeated measures, adjusting for baseline covariates. Results: A total of 225 PEMBRO and 187 IPI+NIVO pts were enrolled, with > 95% questionnaire completion rates through week 24. At baseline, PEMBRO pts were more likely > age 65 (49% vs 37%, p = .011), stage IV disease (92% vs 85%; p = .002), and higher comorbidity index (1.0 vs 0.6; p < .001) compared with IPI+NIVO pts. Adjusted EORTC global health status/quality of life (GHS) LS mean changes from baseline showed greater improvement with PEMBRO vs. IPI+NIVO at 12, 18 and 24 weeks. At week 24, PEMBRO pts achieved a 3.3-point improvement (95% CI = 0.8, 5.7) and IPI+NIVO pts had no significant change (1.0, 95% CI = -1.6, 3.5), with a LS mean difference of 2.3 points (p = .037; 95% CI = 0.14, 4.51). At week 24, the EQ-5D visual analogue scale increased 1.0 (95% CI, -1.2, 3.2) for PEMBRO vs IPI+NIVO which decreased 0.9 (95% CI = -3.2, 1.3), with a statistically significant LS mean difference of 2.0 (95% CI = 0.4, 3.9; p = .045). Conclusions: Results from 2 measures suggest HRQoL was maintained vs. baseline in both PEMBRO and IPI+NIVO pts, with a significant between-group difference favoring PEMBRO in GHS over 24 weeks.

Genetic and epigenetic alterations are essential for the initiation and progression of human cancer. We previously reported that primary human medulloblastomas showed extensive cancer-specific CpG island DNA hypermethylation in critical developmental pathways. To determine whether genetically engineered mouse models (GEMMs) of medulloblastoma have comparable epigenetic changes, we assessed genome-wide DNA methylation in three mouse models of medulloblastoma. In contrast to human samples, very few loci with cancer-specific DNA hypermethylation were detected, and in almost all cases the degree of methylation was relatively modest compared with the dense hypermethylation in the human cancers. To determine if this finding was common to other GEMMs, we examined a Burkitt lymphoma and breast cancer model and did not detect promoter CpG island DNA hypermethylation, suggesting that human cancers and at least some GEMMs are fundamentally different with respect to this epigenetic modification. These findings provide an opportunity to both better understand the mechanism of aberrant DNA methylation in human cancer and construct better GEMMs to serve as preclinical platforms for therapy development.

O1 IL-15 primes an mTOR-regulated gene-expression program to prolong anti-tumor capacity of human natural killer cells #### Andreas Lundqvist1, Vincent van Hoef1, Xiaonan Zhang1, Erik Wennerberg2, Julie Lorent1, Kristina Witt1, Laia Masvidal Sanz1, Shuo Liang1, Shannon Murray3, Ola Larsson1

Rhabdomyosarcoma is the most common soft-tissue sarcoma in children. While cytogenetic abnormalities have been well characterized in this disease, aberrant epigenetic events such as DNA hypermethylation have not been described in genome-wide studies. We have analyzed the methylation status of 25,500 promoters in normal skeletal muscle, and in cell lines and tumor samples of embryonal and alveolar rhabdomyosarcoma from pediatric patients. We identified over 1,900 CpG islands that are hypermethylated in rhabdomyosarcomas relative to skeletal muscle. Genes involved in tissue development, differentiation, and oncogenesis such as DNAJA4, HES5, IRX1, BMP8A, GATA4, GATA6, ALX3, and P4HTM were hypermethylated in both RMS cell lines and primary samples, implicating aberrant DNA methylation in the pathogenesis of rhabdomyosarcoma. Furthermore, cluster analysis revealed embryonal and alveolar subtypes had distinct DNA methylation patterns, with the alveolar subtype being enriched in DNA hypermethylation of polycomb target genes. These results suggest that DNA methylation signatures may aid in the diagnosis and risk stratification of pediatric rhabdomyosarcoma and help identify new targets for therapy.

9571Background: Both pembrolizumab (PEMBRO) and the combination of ipilimumab and nivolumab (IPI+NIVO) are approved by the US FDA for treatment of advanced (unresectable or metastatic) melanoma. Cl...

10525Background: In the phase 1 portion of KEYNOTE-051 (NCT02332668), the 2-mg/kg-Q3W dose of pembro was identified as the pediatric recommended phase 2 dose. We provide an update on the safety and...

108Background: In a phase 1/2 study, the combination of E, a selective oral inhibitor of the IDO1 enzyme, plus P, a PD-1 inhibitor, suggested promising antitumor activity with minimal additive toxicity. ECHO-301/KEYNOTE-252 (NCT02752074) is a phase 3, randomized, double-blind study evaluating the efficacy and safety of E + P vs placebo + P in pts with untreated unresectable or metastatic melanoma. Methods: Pts had histologically confirmed unresectable stage III or IV melanoma and were treatment naive for advanced or metastatic disease, except for pts with the BRAF V600 mutation who could have received prior BRAF/MEK therapy. Pts were stratified by PD-L1 expression and BRAF mutation status (BRAF mutant with prior BRAF-directed therapy, BRAF mutant without prior BRAF-directed therapy, and BRAF wild type) and randomized 1:1 to E 100 mg BID + P 200 mg Q3W or matched E placebo + P 200 mg Q3W. Response was assessed per RECIST v1.1 and irRECIST (both by central review). The primary endpoints were PFS per RECIST ...

e21500Background: Pembrolizumab (PEMBRO) is the first US FDA approved PD-1 antibody for the treatment of patients with advanced (metastatic/unresectable) melanoma. Clinical trials such as KEYNOTE-0...

10525 Background: In phase 1 of the KEYNOTE-051 study (NCT02332668), the 2 mg/kg Q3W approved adult dose of pembro was also determined to be the pediatric recommended phase 2 dose. In phase 2, presented herein, we further evaluated this dose in pediatric pts with advanced cancer. Methods: Children aged 6 mo to < 18 y with advanced melanoma or a PD-L1+ advanced, relapsed or refractory solid tumor or lymphoma, measurable disease per RECIST v1.1, and performance score ≥50 using Lansky Play or Karnofsky scales received pembro 2 mg/kg Q3W for 35 cycles or until confirmed disease progression per immune-related RECIST by investigator review, intolerable toxicity, or pt/investigator decision to discontinue. Tumor imaging was performed every 8 wk for the first 6 mo, then every 12 wk thereafter. AEs were graded by NCI CTCAE v4.0. Key efficacy endpoints were ORR, disease control rate (DCR), and PFS per RECIST v1.1 by investigator and OS. Results: Of 369 pts prescreened, 364 were evaluable for PD-L1 expression; of these, 121 (33.2%) were PD-L1+. 66 pts were enrolled; median follow-up was 2.5 mo (range, 0.2-18). As of the data cutoff (Nov 7, 2016), 23 (34.8%) pts were still on treatment. Median age was 13 y (range, 1-17), 77.3% had metastatic disease, and 34.8% had ≥3 prior lines of therapy for recurrent/metastatic disease. Primary diagnoses were non-CNS solid tumors (n = 45), CNS tumors (n = 16), and lymphoma (n = 5). 5 (7.6%) pts had grade 3-4 treatment-related AEs (TRAEs), most commonly neutropenia (n = 2). No treatment-related deaths occurred; 1 pt discontinued for a TRAE (grade 3 AST increased). 1 pt each with Hodgkin lymphoma, adrenocortical carcinoma, mesothelioma, and glioblastoma had partial response for an ORR of 6.1% (95% CI, 1.7-14.8); 7 (10.6%) pts had stable disease for a DCR of 16.7% (95% CI, 8.6-27.9). Median PFS and OS were 1.8 mo and 9.2 mo, respectively; 12-mo PFS was 10.2% and OS was 40.5%. Potential effects of pembro on the developing immune system (eg, T and B cells, vaccinated antibodies) will also be presented. Conclusions: Pembro showed low toxicity and warrants further study to determine activity in select pediatric tumors. Enrollment in KEYNOTE-051 is ongoing. Clinical trial information: NCT02332668.

TPS10585Background: Pembro, a highly selective humanized monoclonal antibody that directly blocks the interaction between programmed death 1 (PD-1) and its ligands PD-L1 and PD-L2, is indicated for...

TPS9598Background: Talimogene laherparepvec, an oncolytic viral immunotherapy, was designed to selectively replicate in tumors resulting in lytic cell death, antigen release, and production of GM-C...

TPS9596Background: The interaction between programmed death 1 (PD-1) and its ligands PD-L1 and PD-L2 represents a major pathway that tumors may use to evade immune control, enabling their survival and progression. Pembro, a highly selective and potent humanized monoclonal antibody that directly blocks PD-1, has demonstrated a manageable toxicity profile with durable responses in advanced melanoma. Inhibition of the MAPK pathway with a combination of BRAF and MEK inhibitors improves survival in BRAFV600-mutant melanoma and may be synergistic with immunotherapies. KEYNOTE-022 (NCT02130466) is a multicenter phase 1/2 study of pembro in combination with D, a selective BRAF inhibitor, and T, a highly selective MEK1/2 inhibitor. In the randomized phase 2 study described here, we will evaluate the safety, tolerability, and preliminary efficacy of this triplet combination as first-line therapy for BRAF-mutant melanoma. Methods: Patients aged ≥ 18 y with histologically confirmed unresectable or metastatic stage II...

e20659Background: Treatment with single agent PD-1 blockade improves survival in patients with chemotherapy-refractory NSCLC, yet only a minority respond. Rational combination approaches are needed...

9503Background: The anti–PD-1 antibody pembro (pembro; MK-3475) prevents PD-1 from binding to its ligands, PD-L1 and PD-L2, and is approved for treating advanced melanoma at a dose of 2 mg/kg every 3 wk (Q3W). Pembro demonstrated superior PFS over chemotherapy for ipilimumab (ipi)-refractory melanoma (KEYNOTE-002) and superior OS and PFS over ipi for advanced melanoma (KEYNOTE-006). We present 3-year OS data for all patients (pts) with melanoma enrolled in the phase 1b KEYNOTE-001 study (NCT01295827). Methods: Pts were enrolled in ipi-naive and ipi-treated cohorts and received pembro 2 or 10 mg/kg Q3W or 10 mg/kg Q2W until intolerable toxicity, progression, or investigator decision. Clinically stable pts with radiographic progression could remain on pembro until progression was confirmed. Response was assessed by RECIST v1.1 every 12 wk. After pembro discontinuation, pts were contacted to assess survival every 3 mo. OS was estimated using the Kaplan-Meier method. Results: Of the 655 pts enrolled, 24% had ...

3014Background: The anti–PD-1 antibody pembro has demonstrated durable responses in ~30%-40% of patients (pts) with advanced melanoma. The combination of BRAF inhibitor D and MEK inhibitor T, the s...

DNA methylation might have a significant role in preventing normal differentiation in pediatric cancers. We used a genomewide method for detecting regions of CpG methylation on the basis of the increased melting temperature of methylated DNA, termed denaturation analysis of methylation differences (DAMD). Using the DAMD assay, we find common regions of cancer-specific methylation changes in primary medulloblastomas in critical developmental regulatory pathways, including Sonic hedgehog (Shh), Wingless (Wnt), retinoic acid receptor (RAR), and bone morphogenetic protein (BMP). One of the commonly methylated loci is the PTCH1-1C promoter, a negative regulator of the Shh pathway that is methylated in both primary patient samples and human medulloblastoma cell lines. Treatment with the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine (5-aza-dC) increases the expression of PTCH1 and other methylated loci. Whereas genetic mutations in PTCH1 have previously been shown to lead to medulloblastoma, our study indicates that epigenetic silencing of PTCH1 , and other critical developmental loci, by DNA methylation is a fundamental process of pediatric medulloblastoma formation. This finding warrants strong consideration for DNA demethylating agents in future clinical trials for children with this disease.