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116 Background: Although immune checkpoint inhibitors (CPI) are inactive as monotherapy for microsatellite stable (MSS) mCRC, preclinical modeling suggests that addition of other immune-oncology agents can produce antitumor activity. CV301 is a poxviral vaccine against CEA and MUC1. N-803 is an IL-15 superagonist. M9241 is tumor-targeted IL-12. Bintrafusp alfa (BA) is a bifunctional anti-PD-L1/TGF-βRII fusion protein. Methods: Patients with advanced MSS or proficient mismatch repair (pMMR) small bowel or CRC were eligible (NCT04491955). Patients enrolling to Arm 1 received triple therapy with BA 1200 mg IV every 2 weeks, N-803 15 mcg/kg SC every 4 weeks, and CV301 SC on D1, D15, D29, and monthly, thereafter. Patients enrolling to Arm 2 received quadruple therapy, with M9241 (8 mcg/kg or 16.8 mcg/kg SC every 4 weeks) plus BA (300 mg or 1200 mg IV), N-803 (10 mcg/kg SC) and CV301 SC, depending on dose escalation schedule. Results: Thirty patients (2 small intestinal, 17 colon, 11 rectal) were treated. All patients had received prior 5-fluorouracil-based treatment, with 29/30 (96.7%) having received ≥ 2 lines of systemic therapy. Twelve patients received triple therapy; 18 received quadruple therapy. Grade 3 treatment-related AEs (TRAEs) occurred in 8 patients (26.7%); anemia occurred most commonly (n = 5), with grade 3 gastrointestinal hemorrhages occurring in 2 patients (on quadruple therapy). Other grade 3 TRAEs included elevated cardiac troponin, AST, and alkaline phosphatase (n = 1 each; all with triple therapy), and adrenal insufficiency (n = 1; quadruple therapy). No grade 4 or 5 TRAEs occurred. Triple therapy resulted in disease reduction in 2 patients (7.5%, 25.6%); quadruple therapy resulted in disease reduction in 2 patients (26.7%, 70.6%). Median overall survival (OS) for triple and quadruple therapy have not been reached, with 12 month survival being 66.7% (95% CI: 33.7-86.0%) for triple therapy and 77.2% (95% CI: 43.3-92.3%) for quadruple therapy. Conclusions: Combination therapies with CV301, N-803, bintrafusp alfa, and M9241 had manageable safety profiles. Preliminary clinical activity was observed in patients with advanced MSS/pMMR small bowel or CRC. Median OS was promising as compared to historical median survivals of 6-7 months following receipt of multiple lines of therapy. Clinical trial information: NCT04491955 . more...

Immune checkpoint blockade (ICB) monotherapy has produced limited benefit in breast cancer (BC) with response rates (RR) ranging from 5 to 23%. Combination ICB improved RR and progression free survival (PFS) resulting in atezolizumab + nab-paclitaxel receiving FDA accelerated approval for programmed cell death ligand 1 (PD-L1) positive, triple negative breast cancers (TNBC). BC has historically been considered immunologically quiet with most having a low mutational burden, low PD-L1 expression, defective antigen presentation machinery, and immuosuppressive signals in the tumor microenvironment (TME). An approach using a combination of immuno-oncology (IO) agents including ICB, immunomodulators and vaccines may shift the TME to allow for improved antigen presentation, the release of immunostimulatory cytokines, more immunogenic cell death and increased PD-L1 expression. The transcription factor brachyury plays an important role in breast tumor plasticity. High brachyury expression is associated with treatment resistance and a worse prognosis. Entinostat is a histone deacetylase inhibitor that has activity in multiple breast cancer subtypes. Preclinical data demonstrates entinostat upregulates MHC, enhances immune-mediated lysis and upregulates PD-L1 expression through epigenetic modification. Bintrafusp alfa is a bifunctional protein composed of the extracellular domain of the TGF-βRII receptor (TGF-β“trap”) fused to a human IgG1. Preclinical data shows bintrafusp alpha treatment increases T-cell trafficking, antigen-specific CD8+ T-cell lysis and NK cell activation. Monotherapy clinical studies with these agents have produced modest results in solid tumors, including BC. Preclinical data evaluating combinations of these agents shows a reduction in in tumor size, improved antigen-specific T-cell responses, reduced regulatory T cells, increased CD8+T-cells, and increased PD-L1 expression. We propose the stepwise addition of BN-Brachyury, Bintrafusp alfa, T-DM1 and Entinostat in advanced BC. This phase Ib study will assess efficacy and safety of the regimen and has three cohorts: Cohort 1(TNBC) will receive BN-Brachyury + Bintrafusp alfa. Cohort 2 (HER2+) will receive T-DM1 + BN-Brachyury + Bintrafusp alfa +/- entinostat. After safety is established in Cohort 2, patients in Cohort 3 (HER2+) will be assigned to receive T-DM1 + BN-Brachyury + Bintrafusp alfa +/- entinostat. Responses are evaluated every 2 cycles (6 weeks). Patients in Cohorts 2 and 3 will undergo research biopsies -baseline and after 2 cycles to evaluate changes within TME. Peripheral immune responses will be evaluated at selected time points. All patients must have measurable disease and HER2+ patients must have biopsiable disease. >1 prior treatment is required. Asymptomatic or brain metastases treated > 6 weeks are allowed. Well controlled HIV, HBV or treated HCV is allowed. Exclusion criteria include symptomatic brain metastases or clinically significant bleeding ( Citation Format: Margaret E Gatti-Mays, Claudia Palena, Sofia R Gameiro, Renee N Donahue, Caroline Jochems, Seth Steinberg, Stan Lipkowitz, Alexandra Zimmer, Deneise Francis, Julius Strauss, Houssein Abdul Sater, Lisa Cordes, Jason Redman, Fatima Karzai, Marijo Bilusic, Ravi A Madan, James L Gulley, Jeffrey Schlom. A phase Ib trial of sequential combinations of BN-brachyury, entinostat, ado-trastuzumab emtansine (T-DM1) and bintrafusp alfa (M7824) in advanced stage breast cancer (BrEAsT) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT1-08-01. more...

Breast tumors commonly harbor low mutational burden, low PD-L1 expression, defective antigen processing/presentation, and an immunosuppressive tumor microenvironment (TME). In a malignancy mostly refractory to checkpoint blockade, there is an unmet clinical need for novel combination approaches that increase tumor immune infiltration and tumor control. Preclinical data have guided the development of this clinical trial combining 1) BN-Brachyury (a poxvirus vaccine platform encoding the tumor associated antigen brachyury), 2) bintrafusp alfa (a bifunctional protein composed of the extracellular domain of the TGF-βRII receptor (TGFβ “trap”) fused to a human IgG1 anti-PD-L1), 3), entinostat (a class I histone deacetylase inhibitor), and 4) T-DM1 (ado-trastuzumab emtansine, a standard of care antibody-drug conjugate targeting HER2). We hypothesize that this tetratherapy will induce a robust immune response against HER2+ breast cancer with improved response rates through 1) expanding tumor antigen-specific effector T cells, natural killer cells, and immunostimulatory dendritic cells, 2) improving antigen presentation, and 3) decreasing inhibitory cytokines, regulatory T cells, and myeloid-derived suppressor cells. In an orthotopic HER2+ murine breast cancer model, tetratherapy induced high levels of antigen-specific T cell responses, tumor CD8+ T cell/Treg ratio, and augmented the presence of IFNγ- or TNFα-producing CD8+ T cells and IFNγ/TNFα bifunctional CD8+ T cells with increased cytokine production. Similar effects were observed in tumor CD4+ effector T cells. Based on this data, a phase 1b clinical trial evaluating the stepwise addition of BN-Brachyury, bintrafusp alfa, T-DM1 and entinostat in advanced breast cancer was designed. Arm 1 (TNBC) receives BN-Brachyury + bintrafusp alfa. Arm 2 (HER2+) receives T-DM1 + BN-Brachyury + bintrafusp alfa. After safety is established in Arm 2, Arm 3 (HER2+) will receive T-DM1 + BN-Brachyury + bintrafusp alfa + entinostat. Reimaging will occur every 2 cycles (1 cycle = 21 days). Arms 2 and 3 undergo research biopsies at baseline and after 2 cycles to evaluate changes within the TME. Peripheral immune responses will be evaluated. Co-primary objectives are response rate and safety. All arms employ a safety assessment in the initial six patients and a 2-stage Simon design for clinical efficacy (Arm 1 if ≥ three responses of eight then expand to 13 patients; Arms 2 and 3 if ≥ four responses of 14 then expand to 19 patients per arm). Secondary objectives include progression-free survival and changes in tumor infiltrating lymphocytes. Exploratory analyses include changes in peripheral immune cells and cytokines. To our knowledge, the combination of a vaccine, an anti-PD-L1 antibody, entinostat, and T-DM1 has not been previously evaluated in the preclinical or clinical setting. This trial (NCT04296942) is open at the National Cancer Institute (Bethesda, MD). more...

Lessons Learned Background Enzalutamide is an established standard-of-care treatment for advanced prostate cancer with a commercially available formulation that may be inconvenient for some patients. We proposed a study to evaluate the bioequivalence of a liquid formulation to provide an alternative method of administration. Methods This was a single-dose, randomized, open-label, two-way crossover pilot bioequivalence study to compare two oral formulations of enzalutamide: four enzalutamide 40 mg liquid-filled soft-gelatin capsules (commercially available) administered whole versus enzalutamide 160 mg liquid (extracted from capsules) administered via oral syringe. To assess bioequivalence, patients were randomized to receive a single dose of one formulation, then cross over to receive the alternative formulation following a 42-day washout period; serial plasma samples were collected over the course of 24 hours, followed by collections at 3, 8, and 42 days after the dose for both formulations. Bioequivalence of the formulations was assessed via comparisons of area under the plasma concentration–time curve (AUC) calculations per U.S. Food and Drug Administration (FDA) guidance. The study also assessed the safety and tolerability of the formulations. Results The study failed to meet proposed accrual, with only one patient enrolled, thus limiting the bioequivalence evaluation. Based on the data from a single patient, the drug exposure (measured by AUC) of enzalutamide and N-desmethyl enzalutamide (primary active metabolite) for the liquid formulation was 112% and 117%, respectively, compared with the capsule formulation. Although both formulations appeared well tolerated with no adverse events reported, the tolerability assessment questionnaire revealed an unpleasant taste of the liquid formulation. Conclusion Preliminary evidence suggests a similar pharmacokinetic profile when administering liquid extracted from enzalutamide soft-gelatin capsules compared with intact capsules in patients with prostate cancer. more...

2501 Background: There are more than 630,000 cases of HPV associated malignancies including cervical, oropharyngeal and anal cancer worldwide annually. HPV 16 is responsible for the majority of these cases. About 15-20% of HPV associated malignancies respond to PD-(L)1 inhibitors, but for the overwhelming majority of patients who progress on these immunotherapies there is no effective standard of care therapy. Preclinical studies have shown that the triple combination of PDS0101 (Versamune-HPV), a liposomal multipeptide therapeutic vaccine targeting HPV 16 E6/E7, M9241, a tumor-targeting immunocytokine composed of IL-12 heterodimers fused to a monoclonal antibody targeting free DNA in necrotic tumor regions, and bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, resulted in maximum HPV-specific T cell responses, T cell tumor infiltration and tumor reduction as compared to any one or two of these agents alone. Methods: Fourteen pts with HPV 16+ relapsed or refractory advanced cancer were enrolled to the triple combination of PDS0101, M9241 and bintrafusp alfa (NCT04287868). Pts received bintrafusp alfa at 1200 mg flat dose i.v. every 2 weeks, M9241 at 16.8 mcg/kg s.c. every 4 weeks and PDS0101 given as two separate 0.5 ml s.c. injections every 4 weeks. Dose reductions of M9241 to 8 mcg/kg were allowed as well as skipped doses of any agent for ongoing toxicities. Results: Fourteen pts with advanced HPV 16+ cancers (5 cervical, 2 vaginal/vulvar, 4 anal, 3 oropharyngeal) were treated. 4/14 (28.6%) pts had a grade 3 treatment related toxicity including grade 3 hematuria in 2 pts with cervical ca and prior pelvic radiation and grade 3 AST/ALT elevation in 2 pts, one with anal ca and one with vaginal ca. For one patient with grade 3 AST/ALT elevation dose reduction of M9241 from 16.8 to 8 mcg/kg allowed for continued treatment with AST/ALT remaining at grade 1 or less. One additional patient had transient asymptomatic grade 4 neutropenia. No other treatment related grade 3 or greater toxicities were noted. 10/14 (71%) pts have had objective responses: 1 CR (anal ca) and 9 PRs (3 cervical, 2 vulvar/vaginal, 2 anal, 2 oropharyngeal) with 9/10 of these responses ongoing after a median 5 month of follow up. Of the 14 pts, 6 pts have checkpoint naïve disease and 8 pts have checkpoint refractory disease. 5/6 (83%) pts with checkpoint naïve disease and 5/8 (63%) pts with checkpoint refractory disease have had objective responses. Analyses of immune responses and other immune correlates are ongoing. Conclusions: Triple combination of PDS0101, M9241 and bintrafusp alfa appears to have a manageable safety profile along with early evidence of notable clinical activity for pts with both checkpoint naïve as well as checkpoint refractory HPV 16+ advanced malignancies. Clinical trial information: NCT04287868. more...

4562 Background: We report the safety and clinical activity of the combination of CaboNivo and CaboNivoIpi in pts with mUC and other mGU tumors (NCT02496208). Methods: In this phase I trial 30 pts were treated in 4 dose levels (DL) for part 1 (CaboNivo) and 18 pts were treated in 3 DL for part 2 (CaboNivoIpi). Pts received Cabo PO daily and Nivo IV (part 1) with Ipi 1mg/kg x 4 doses q3wks (part 2). A mUC and a renal cell carcinoma (RCC) expansion cohort of CaboNivo has initiated enrollment. Tumors were assessed for overall response rate (ORR) q8wks (RECIST 1.1). Adverse events (AEs) were graded (G) by NCI-CTCAE v4.0. Results: From 7/22/15 to 12/31/2016, 48pts (CaboNivo N = 30; CaboNivoIpi N = 18) (mUC N = 19; bladder urachal N = 4; bladder squamous cell carcinoma (bSCC) N = 2; germ cell tumor (GCT) N = 4; castrate-resistant prostate cancer (CRPC) N = 9; RCC N = 2, sarcomatoid RCC N = 2, Sertoli cell N = 1, and trophoblastic tumor N = 1 were treated. Median age was 58 (range 35-77), 41 (85%) were male. Common treatment-related G1/2 AEs for CaboNivo: ALT increase (67%), fatigue (63%), diarrhea (60%), hypothyroidism (57%); CaboNivoIpi: fatigue (72%), diarrhea (61%), anorexia (61%); Grade 3 AEs for CaboNivo: hypertension (23%), neutropenia (17%), hypophosphatemia (13%), lipase increase (10%), fatigue (7%), aseptic meningitis (3%); CaboNivoIpi: hypophosphatemia (19%), hypertension (19%), fatigue (13%), hyponatremia (13%), nausea (13%), lipase increase (11%), colitis (6%); G4 CaboNivo: lipase increase (7%) thrombocytopenia (3%); CaboNivoIpi lipase increase (6%) There were no G5 toxicities, no DLTs. 43 pts were evaluable for response: ORR was 30% 13/43 [3 CR (2 mUC, 1 bSCC); 10 PRs (4 mUC, 2 penile, 1 sarcomatoid RCC, 1 urachal, 1 CRPC, 1 bSCC)]. ORR for CaboNivo 39% (mUC 44%); CaboNivoIpi 18% (mUC 29%). 11/13 (85%) of responses were ongoing at cutoff. Conclusions: CaboNivo and CaboNivoIpi combinations were well tolerated with no DLTs and have durable efficacy in mGU tumors particularly mUC. Rare tumors such as bSCC, urachal, and penile cancers demonstrated response to the combination. Larger cohorts of mUC and rare GU tumors are ongoing. Clinical trial information: NCT02496208. more...

e16017 Background: The primary objective of the study is to assess the feasibility of obtaining combined FDG and NaF PET/CT in detecting soft-tissue and bone metastatic disease in mGU pts treated with CaboNivo+/-Ipi. Methods: Pts in this single-arm, multicenter, phase I trial had FDG PET/CT followed by NaF PET/CT within 1 hour, at baseline and 8 weeks. The number and location of metastatic lesions on FDG PET/CT and on NaF PET/CT were captured. Lesions were considered positive when there was focal abnormal radiotracer uptake with CT correlation. We analyzed soft tissue and bone lesions distribution and the concordance of baseline metastatic bone disease. Results: From 7/14/15 to 9/9/16, 27 pts (urothelial carcinoma N = 11, bladder squamous cell carcinoma N = 2, sarcomatoid renal cancer N = 1, sertoli cell N = 1, germ cell tumor N = 4, trophoblastic testicular cancer N = 1, urachal N = 4, castrate-resistant prostate cancer N = 2, prostate neuroendocrine N = 1) had scans. Median age was 55 (range 35-75 yr), 24 (89%) were male. Pts completed the dual PET/CTs on the same day (imaging time 3-4 hours) without complications. On FDG, the distribution of 340 lesions were lymph node 41%, bone 35%, lung 18%, liver 11%, soft tissue 4%, kidney 0.6%, adrenal 0.3%, spleen 0.3%, pancreas 0.3%. On NaF, the distribution of 130 lesions was spine 33%, rib 16%, pelvis 13%, femur 10%, scapula 9%, sacrum 8%, skull 5%, humerus 4%, sternum 3%, manubrium 2%, clavicle 2%. Of the 130 lesions on FDG/NaF PET/CT, 38% were not seen on initial FDG. The combination of the two tracers did not affect the quality of the PET/CTs given distinct radiotracer uptake in the anatomical locations with no distortions. Residual FDG activity on combined FDG-NaF images required background intensity to be adjusted to delineate focal radiotracer uptake. There was no difficulty in identifying metastatic lesions, and no instances of prior FDG uptake affecting the determination of metastatic disease. Conclusions: Combination FDG-NaF PET/CT is a feasible imaging modality that offers convenience to pts without compromising detection of metastatic disease in mGU pts. FDG alone detected fewer bone lesions than combined FDG-NaF PET/CT. Clinical trial information: NCT02496208. more...

293 Background: We report the safety and clinical activity of CaboNivo and CaboNivoIpi in pts with mUC and other GU tumors. Methods: Part I included 4 dose levels (DLs) (Cabo PO daily and Nivo IV q2wk): DL1 Cabo40/Nivo1, DL2 Cabo40/Nivo3, DL3 Cabo60/Nivo1, DL4 Cabo 60/Nivo3. Part II included 3 DLs (Cabo PO daily, plus NivoIpi IV q3 wk x 4 doses then Nivo q2wk): DL5 Cabo 40/Nivo1/Ipi1, DL6 Cabo40/Nivo3/Ipi1, DL7 Cabo 60/Nivo3/Ipi 1. Tumors were assessed for overall response rate (ORR) by RECIST 1.1. Adverse events (AEs) were graded (G) by NCI-CTCAE v4.0. Results: From 7/22/15-10/14/16, 40pts [mUC N=14/(plasmacytoid N=1); bladder urachal N=4; bladder squamous cell carcinoma (bSCC) N=2; germ cell tumor (GCT) N=4; castrate-resistant prostate cancer (CRPC) N=9/(neuroendocrine prostate N=1); sarcomatoid renal cell carcinoma (sRCC) N=1; trophoblastic tumor N=1); sertoli cell tumor N=1; and penile SCC N=4] were treated. Median age was 58 (range 31-77); 36 (90%) were male. AEs related to study drugs with [1] CaboNivo included G3 hyponatremia 4/24 (17%), hypophosphatemia 4/24 (17%), lipase increase 3/24 (13%), dehydration 2/24 (8%), diarrhea 2/24 (8%), fatigue 2/24 (8%), HTN 2/24 (8%), thromboembolic event 1/24 (4%), rash 1/24 (4%), chest pain 1/24 (4%), amylase increase 1/24 (4%), hyperthyroid 1/24 (4%), proteinuria 1/24 (4%), thrombocytopenia 1/24 (4%); and G4 pyelonephritis 1/24 (4%); [2] CaboNivoIpi included G3 hypophosphatemia 2/16 (13%), lipase increase 2/16 (13%), fatigue 1/16 (6%), ALT increase 1/16 (6%), and HTN 1/16 (6%). There were 2/40 (5%) G3 immune-related AEs: 1 aseptic meningitis/CaboNivo; and 1 colitis/CaboNivoIpi. There were no G5 toxicities, or DLTs. 38 pts were evaluable for response. ORR was 12/38 (32%): 1 CR (bSCC); 11 PRs (5 mUC, 1 sRCC, 1 urachal, 1 bSCC, 1 CRPC, 2 penile). SD 20/38 (53%); 9/11 responses were ongoing and 26/39 (67%) pts remain on study. Conclusions: CaboNivo and CaboNivoIpi were well tolerated with no DLTs. Responses were seen at all DLs. The recommended dose for Part I is Cabo40/Nivo3 and for Part II is Cabo40/Nivo3/Ipi1. Rare tumors such as bSCC, urachal, and penile cancer demonstrated responses. Clinical trial information: NCT02496208. more...

317 Background: This study investigates whether changes in 18F-FDG-PET/CT correlate with response to cabozantinib at an early time point (4 wks) versus the conventional time point of restaging (8 wks) in pts with mUC, using Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST). Methods: 68 pts with mUC in a single arm phase II clinical trial of cabozantinib underwent FDG-PET/CT scans at baseline, 4 and 8 wks. Up to 5 lesions with the highest Standard Uptake Value (SUV) were designated as target lesions. Response was determined using 2 versions of PERCIST (1 lesion vs top 5 lesions with highest FDG uptake) for FDG-PET/CT at 4 and 8 wks. PERCIST response classifications were compared to RECIST v1.1 at 8 wks. Results: 54 pts had evaluable disease. The single lesion 4 wk response by PERCIST showed 40% partial metabolic response (PMR), 33% stable metabolic disease (SMD), and 27% progressive metabolic disease (PMD). The single lesion 8 wk response by PERCIST showed 31% PMR, 31% SMD, and 38% PMD. The single lesion analysis coincided with multiple lesion PERCIST analysis in 86% of pts at 4 wks and 89% at 8 wks. The 4 wk PET/CT was predictive of the 8 wk PET/CT in 75% of single lesion and 76% of multiple lesion analyses. In lesion-based analysis, the 4 wk PET/CT was predictive of the 8 wk PET/CT in 74% of bone, 89% of lung, 77% of lymph node, 74% of soft tissue, and 58% of liver lesions. Only 42% of the 8 wk PERCIST and RECIST classifications coincided. At 8 wks, 40% showed response in FDG PET-CT restaging vs 7% complete/partial response by RECIST. Conclusions: The 4 wk PET/CT scan predicts the therapy response at the 8 wk PET/CT scan however the 4 wk scan overestimates the 8 wk response. The single lesion analysis by PERCIST correlates with the multiple lesion analysis and may have more clinical utility. In the lesion-based analysis, the 4 wk PET/CT scan is predictive of the 8 wk PET/CT for bone, lung, lymph node and soft tissue but not for liver lesions. Response classifications by PERCIST are not in agreement with response classifications by RECIST. Although the methods may be complementary, they are not interchangeable. Further studies are required to validate these findings. Clinical trial information: NCT01688999. more...

328 Background: NaF PET/CT is a radiotracer used for the assessment of bone metastases (mets). The goal of our study was to assess bone mets using NaF PET/CT imaging in mUC pts treated with cabozantinib. Methods: We conducted a single-arm phase II trial of cabozantinib in pts with mUC. Pts with known bone mets underwent a NaF PET/CT scan at baseline and every 8 weeks until progression. At each scan, we captured, the number of lesions per pt and per anatomical site, the maximum standardized uptake values (SUV), and serum alkaline phosphatase (AP). Bone responses (bone response (BR), stable disease (SD), progressive disease (PD)) were assigned to each pt based on the NaF report. Change from baseline to the time of best response for SUV, the number of lesions, and AP were compared between BR + SD vs PD were analyzed using an exact Wilcoxon rank sum test. The Kaplan-Meier method was used to determine the association of progression free survival (PFS) or overall survival (OS) with baseline SUV and number of lesions. Results: 68 pts enrolled on study, 22 pts had bone mets at baseline (6 bone only and 16 with bone and soft-tissue mets) (median OS 4.6 mo (95% CI: 3.4-7.7 mo), and median PFS 2.0 mo (95% CI: 1.8-3.9 mo)) of which 15 pts had follow up NaF scans. At baseline, 147 total lesions were analyzed, and the lesion distribution was: spine 29%, ribs 21%, pelvis 18%, skull 11%, femur 6%, scapula 3%, humerus 3%, sternum 3%, sacrum 3%, fibula 1%, and clavicle 0.7%. 5/15 pts had BR (and remained on study 238, 252, 182, 161, and 56 days), 4/15 SD, and 6/15 PD at best response. Sites of PD occurred in bone 10/22, bone and soft-tissue 5/22, and soft-tissue 7/22. The percent difference in number of lesions among responders and non-responders was 43% (p = 0.0039). At baseline, there was no association with PFS or OS and number of lesions (p = 0.84, p = 0.97), SUV (p = 0.83, p = 0.97), or AP (p = 0.97, p = 0.33). Conclusions: Pts with mUC and bone disease have poor overall outcome. Most bone lesions were found in the spine, ribs, and pelvis. Larger studies are needed to assess the correlation of NaF response with clinical outcome in mUC. We have an ongoing study using NaF PET to assess bone mets in mUC treated with cabozantinib/nivolumab/ipilimumab. Clinical trial information: NCT01688999. more...

307 Background: Translational studies have shown that shed MET levels in serum and urine of pts with UC correlate with stage and visceral metastases and that cabozantinib reverses HGF-driven UC cell growth and invasion. These data support the evaluation of cabozantinib in pts with mUC. Methods: In this phase II study, pts receive cabozantinib 60 mg daily in 28-day cycles. There are 3 study cohorts (1) mUC, (2) bone only mUC (3) metastatic rare bladder histology. The primary objective is to determine the response rate (RR) by RECIST. Response is assessed every 2 cycles. Tissue, blood, and urine were collected on all pts to test for MET/HGF and immune subsets. Results: 26 out of 55 pts have enrolled (19 M, 7 F): median age 62 (42-82) and median KPS of 80%. Primary sites include bladder (77%) and upper tract UC (23%). Prior therapy includes 30% pts with 1 regimen, 39% with 2, 15% with 3, 8% with 4 and 8% with 6. 81% of pts had visceral metastases (lung, liver and bone) and 19% lymph node only metastases. 23 pts (19 in cohort 1, 3 in cohort 2 and 1 in cohort 3) were evaluable for response after completing at least 4 weeks of therapy. In cohort 1, 2 pts achieved PR (1 remained on study for 10 months and 1 remains on study after >12 months of therapy); 7 pts had SD for at least 16 weeks (1 remained on study for 11 months); 10 had PD; 1 is too early to assess for response; 1 was removed before restaging for toxicity and 1 was removed for not meeting eligibility. The objective RR is 11% and SD 37% for a clinical benefit of 48%. In cohort 2, 1 of 3 pts had a near resolution of bone lesions on NaF PET/CT for 11 months. In cohort 3, only pt enrolled (squamous cell carcinoma of the bladder) achieved SD for 16 weeks. Mixed responses with regression of lung, bone or lymph nodes were observed in 30% of pts with PD. Grade 3/4 toxicities included: fatigue (8%), hyponatremia (8%), hypophosphatemia (8%) diarrhea (4%), thromboembolism (4%), transaminitis (4%), hypothyroidism (4%), thrombocytopenia (4%), dysphonia (4%), hypomagnesemia (4%), creatinine increase (4%) and proteinuria (4%). Conclusions: Cabozantinib has clinical activity in pts with relapsed or refractory mUC with manageable toxicities. Further studies are underway to correlate response to therapy with MET expression. Clinical trial information: NCT01688999. more...

e15503 Background: Assessment of tumor burden change is crucial in clinical trials and patient care. We compared cabozantinib-induced volume changes of all metastatic tumor lesions, total tumor les... more...

e15501 Background: CTC evaluation has the potential to guide precision cancer therapy. Ideally, this analysis can be performed on the day blood is drawn, in the same institution, using compact inst... more...