Infante, Jeffrey R.

Background: Ciltacabtagene autoleucel (cilta-cel; JNJ-68284528; LCAR-B38M CAR-T cells) is a chimeric antigen receptor T (CAR-T) cell therapy with 2 B-cell maturation antigen-targeting single-domain antibodies designed to confer avidity. In the phase 1 LEGEND-2 study in China, LCAR-B38M yielded deep, durable responses with a manageable safety profile in patients (pts) with relapsed/refractory multiple myeloma (R/R MM). The phase 1b/2 CARTITUDE-1 study (NCT03548207) is further evaluating cilta-cel in this pt population in the US. We present updated data from the phase 1b portion along with initial phase 2 data. Methods: Eligible pts (aged ≥18 y) were diagnosed with MM per International Myeloma Working Group (IMWG) criteria and had measurable disease, Eastern Cooperative Oncology Group performance status ≤1, received ≥3 prior regimens or were double-refractory to a proteasome inhibitor and immunomodulatory drug, and received an anti-CD38 antibody. After apheresis, bridging therapy was permitted. Cyclophosphamide 300 mg/m2 and fludarabine 30 mg/m2 daily for 3 d were used for lymphodepletion. A single infusion of cilta-cel at a target dose of 0.75×106 (range 0.5-1.0×106) CAR+ viable T cells/kg was administered 5-7 d after start of lymphodepletion. The primary objective of the phase 1b portion was to characterize cilta-cel safety and establish the recommended phase 2 dose; the primary objective of the phase 2 portion was to evaluate cilta-cel efficacy. Response was assessed per IMWG criteria and minimal residual disease (MRD) by next-generation sequencing. Adverse events (AEs) were graded using CTCAE v5.0. In the phase 1b portion, cytokine release syndrome (CRS) was graded by Lee et al (Blood 2014) and neurotoxicity by CTCAE v5.0; in the phase 2 portion, CRS and neurotoxicity were graded by American Society for Transplantation and Cellular Therapy (ASTCT) criteria. In this combined analysis, Lee et al and CTCAE v5.0 were mapped to ASTCT criteria for CRS and immune effector cell-associated neurotoxicity syndrome (ICANS), respectively. Results: As of the May 20, 2020 clinical cutoff, 97 pts (58.8% male; median age 61.0 y [range 43-78]) with R/R MM received cilta-cel (29 in phase 1b; 68 in phase 2). Median follow-up duration was 8.8 mo (range 1.5-20.4). Pts had received a median of 6 prior lines of therapy (range 3-18); 83.5% were penta-exposed, 87.6% were triple-refractory, 41.2% were penta-refractory, and 97.9% were refractory to last line of therapy. Overall response rate per independent review committee (primary endpoint) was 94.8% (95% CI 88.4-98.3), with a stringent complete response rate of 55.7% (95% CI 45.2-65.8), very good partial response rate of 32.0% (95% CI 22.9-42.2), and partial response rate of 7.2% (95% CI 3.0-14.3). All pts achieved a reduction in M-protein. Median time to first response was 1.0 mo (range 0.9-5.8; 80.4% ≤1.0 mo), and median time to complete response or better was 1.8 mo (range 0.9-12.5; 74.1% ≤3.0 mo); responses deepened over time (Figure). Median duration of response was not reached (NR). Of 52 MRD-evaluable pts, 94.2% were MRD-negative at 10-5. The 6-mo progression-free survival (PFS) and overall survival (OS) rates (95% CI) were 87.4% (78.9-92.7) and 93.8% (86.7-97.2), respectively; median PFS and OS were NR. Ten deaths occurred during the study; 8 were due to AEs (both related and unrelated; CRS/hemophagocytic lymphohistiocytosis, neurotoxicity, respiratory failure, sepsis, septic shock, pneumonia, lung abscess, and acute myelogenous leukemia [n=1 each]), and 2 due to progressive disease. AEs reported in >70% of pts were CRS (94.8%; grade [gr] 3/4 4.1%), neutropenia (90.7%; gr 3/4 90.7%), anemia (81.4%; gr 3/4 68.0%), and thrombocytopenia (79.4%; gr 3/4 59.8%). Median time to CRS onset was 7.0 d (range 1-12) and median duration 4.0 d (range 1-27, excluding n=1 with 97 d). CAR-T cell-related neurotoxicity was reported in 20.6% of pts (gr 3/4 10.3%). Cilta-cel CAR+ T cells showed maximum peripheral expansion at 14 d (range 9-43). Among pts with 6 mo' individual follow-up, 67% had cilta-cel CAR+ T cells below the level of quantification (2 cells/µL) in peripheral blood. Conclusions: Preliminary phase 1b/2 data from CARTITUDE-1 indicate a single low-dose infusion of cilta-cel leads to early, deep, and durable responses in heavily pretreated pts with MM with a safety profile consistent with LEGEND-2. Further investigation of cilta-cel in other MM populations is underway. Disclosures Madduri: Celgene: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Foundation Medicine: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Legend: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau; Kinevant: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau. Berdeja:Teva: Research Funding; Bluebird: Research Funding; Bioclinica: Consultancy; Celgene: Consultancy, Research Funding; EMD Sorono: Research Funding; Kite Pharma: Consultancy; Prothena: Consultancy; Cellularity: Research Funding; Karyopharm: Consultancy; Servier: Consultancy; Legend: Consultancy; Poseida: Research Funding; Lilly: Research Funding; Acetylon: Research Funding; CURIS: Research Funding; Janssen: Consultancy, Research Funding; Genentech, Inc.: Research Funding; Glenmark: Research Funding; Takeda: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Constellation: Research Funding; CRISPR Therapeutics: Consultancy, Research Funding; Vivolux: Research Funding; Abbvie: Research Funding; Amgen: Consultancy, Research Funding; Kesios: Research Funding; Novartis: Research Funding. Usmani:Celgene: Other; BMS, Celgene: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; GSK: Consultancy, Research Funding; Pharmacyclics: Research Funding; Merck: Consultancy, Research Funding; Abbvie: Consultancy; Sanofi: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; Janssen: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; SkylineDX: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Incyte: Research Funding; Array Biopharma: Research Funding; Amgen: Consultancy, Honoraria, Other: Speaking Fees, Research Funding. Jakubowiak:Adaptive, Juno: Consultancy, Honoraria; AbbVie, Amgen, BMS/Celgene, GSK, Janssen, Karyopharm: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Cohen:Celgene: Membership on an entity's Board of Directors or advisory committees; Takeda,: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Other: Patents/Intellectual property licensed, Research Funding. Stewart:Janssen, BMS, Sanofi-Aventis, GSK: Honoraria; Tempus, Inc., Genomics England LLC: Membership on an entity's Board of Directors or advisory committees. Hari:Amgen: Consultancy; BMS: Consultancy; GSK: Consultancy; Janssen: Consultancy; Takeda: Consultancy; Incyte Corporation: Consultancy. Htut:City of Hope Medical Center: Current Employment. Munshi:OncoPep: Consultancy, Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; BMS: Consultancy; Janssen: Consultancy; Adaptive: Consultancy; Legend: Consultancy; Amgen: Consultancy; Karyopharm: Consultancy; Takeda: Consultancy; AbbVie: Consultancy; C4: Current equity holder in private company. Deol:Novartis: Consultancy; Kite, a Gilead Company: Consultancy. Lesokhin:BMS: Consultancy, Honoraria, Research Funding; Genentech: Research Funding; Janssen: Research Funding; Juno: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Serametrix Inc.: Patents & Royalties; GenMab: Consultancy, Honoraria. Singh:Janssen: Current Employment. Zudaire:Janssen: Current Employment. Yeh:Janssen: Current Employment. Allred:Janssen: Current Employment. Olyslager:Janssen: Current Employment. Banerjee:Janssen: Current Employment. Goldberg:Johnson & Johnson: Current Employment, Current equity holder in publicly-traded company. Schecter:Janssen: Current Employment. Jackson:Janssen: Current Employment; Memorial Sloan Kettering Cancer Center: Consultancy. Deraedt:Janssen: Current Employment, Current equity holder in publicly-traded company. Zhuang:Janssen: Current Employment. Infante:Janssen: Current Employment. Geng:Legend Biotech USA Inc.: Current Employment. Wu:Legend Biotech USA Inc.: Current Employment. Carrasco:Legend Biotech USA Inc.: Current Employment. Akram:Legend Biotech USA Inc.: Current Employment. Hossain:Legend Biotech USA Inc.: Current Employment. Rizvi:Legend Biotech USA Inc.: Current Employment. Fan:Legend Biotech USA Inc.: Current Employment. Jagannath:BMS, Janssen, Karyopharm, Legend Biotech, Sanofi, Takeda: Consultancy. Lin:Kite, a Gilead Company: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Merck: Research Funding; Legend BioTech: Consultancy; Juno: Consultancy; Bluebird Bio: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy; Vineti: Consultancy; Takeda: Research Funding; Gamida Cells: Consultancy; Sorrento: Consultancy, Membership on an entity's Board of Directors or advisory committees. Martin:AMGEN: Research Funding; Seattle Genetics: Research Funding; Janssen: Research Funding; GSK: Consultancy; Sanofi: Research Funding.

Abstract Purpose: The safety and preliminary efficacy of MEDI1873, an agonistic IgG1 fusion protein targeting glucocorticoid-induced TNF receptor–related protein (GITR), were evaluated in an open-label, first-in-human, phase I, dose escalation study in previously treated patients with advanced solid tumors. Patients and Methods: Two single-patient cohorts at 1.5 and 3 mg i.v. were followed by 3+3 dose escalation in six cohorts at 7.5, 25, 75, 250, 500, and 750 mg, all every 2 weeks, for up to 52 weeks. Primary endpoints were safety and tolerability, dose-limiting toxicities (DLT), and MTD. Secondary endpoints included antitumor activity, pharmacokinetics, immunogenicity, and pharmacodynamics. Results: Forty patients received MEDI1873. Three experienced DLTs: grade 3 worsening tumor pain (250 mg); grade 3 nausea, vomiting, and headache (500 mg); and grade 3 non-ST segment elevation myocardial infarction (750 mg). An MTD was not reached and treatment was well tolerated up to 500 mg. Most common treatment-related adverse events were headache (25%), infusion-related reaction (17.5%), and decreased appetite (17.5%). MEDI1873 exposure was dose proportional. Antidrug–antibody incidence was low. MEDI1873 increased peripheral CD4+ effector memory T-cell proliferation as well as cytokines associated with effector T-cell activation at dose levels ≥75 mg. The best response was stable disease (SD) in 17 patients (42.5%), including 1 unconfirmed partial response. Eight patients (20.0%) had SD ≥24 weeks. Conclusions: MEDI1873 showed acceptable safety up to 500 mg i.v. every 2 weeks with pharmacodynamics activity, and prolonged SD in some patients. However, further development is not planned because of lack of demonstrated tumor response.

Abstract Background: Familial adenomatous polyposis (FAP) is the most common hereditary polyposis syndrome. It is an autosomal dominant inherited disorder characterized by the early onset of hundreds to thousands of adenomatous polyps throughout the colon. If left untreated, nearly all individuals with this syndrome develop colorectal cancer (CRC) by the third decade of life. Prophylactic colectomy is the standard of care, but individuals remain at risk for malignant transformation of duodenal polyps, rectal polyps for those who have undergone rectal-sparing surgeries, and ileal pouch polyps for those with ileal pouch-anal anastomoses. Multiple studies with both nonselective and selective cyclooxygenase inhibitors (such as sulindac or celecoxib) have shown that anti-inflammatory agents may prevent the formation and inhibit the growth of colorectal adenomatous polyps. However, toxicities associated with these agents and their limited efficacy have prevented their further development. Therefore, there is a high unmet need for novel treatment options to reduce polyp burden, delay or eliminate the need for colectomy and recurrent rectal surgery, and intercept the development of adenocarcinomas in individuals with FAP. Polyps from individuals with FAP display inflammatory features associated with the activation of the IL-23/IL-17/JAK/STAT3 pathway. This inflammation is thought to contribute to further carcinogenesis, culminating in tumor development. Specifically, IL-23 is linked to tumor growth and progression in CRC, and adenomas with high-grade dysplasia showed elevated levels of IL-17A and pSTAT3. Guselkumab, a human monoclonal antibody directed against the p19 subunit of IL-23, specifically targets IL-23 and inhibits its interaction with the IL-23 receptor. Pre-clinical models suggest that inhibition of IL-23 signaling will result in less inflammation and reduce tumor development. Methods: This randomized, blind, placebo-controlled study will evaluate the safety and efficacy of guselkumab in adults with FAP (genetic or clinical diagnosis) who have already undergone colectomy. Polyps with a sum of diameters ≥10 mm in the rectum or pouch are required. Subjects will be randomized equally to one of three study arms: 100 mg, 300 mg, or placebo given subcutaneously every 4 weeks for 6 doses. The primary efficacy endpoint is percentage change from baseline in rectal/pouch polyp burden after 24 weeks. Secondary efficacy endpoints include duodenal polyp burden change and changes in InSiGHT and Spigelman staging. Exploratory translational research objectives will explore changes in RNA expression profiles, epigenomic profiles, cytokine levels, and the microbiome. Exclusion criteria include prior IL-23 targeted therapies and any polyps >1 cm that cannot be removed. While participating, subjects are required to stop any other FAP-directed drug therapy except for aspirin. As of January 2019, 18% of the planned 72 subjects have been enrolled. ClinicalTrials.gov Identifier: NCT03649971. Citation Format: Eduardo Vilar-Sanchez, Carol Burke, Marcia R. Cruz Correa, Evelien Dekker, William M. Grady, Philippe Grandval, Bryson W. Katona, Xavier Llor, Douglas L. Riegert-Johnson, Jean-Christophe Saurin, Peter Stanich, Daniel A. Sussman, David Weinberg, Edward F. Attiyeh, Devanand Joseph, Kelly Raybold, Gary V. Borzillo, Thomas J. Prior, Michael Smith, Hong Xie, Kurtis E. Bachman, Jeffrey R. Infante, Niloy Jewel Samadder. A phase 1b, multicenter, randomized, blinded, placebo-controlled study to evaluate the efficacy of guselkumab in subjects with familial adenomatous polyposis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT236.

9016 Background: The MAP kinase (MAPK) pathway is of critical importance for keratinocyte proliferation and maturation and is essential for epidermal homeostasis. Occurrence of hyperproliferative skin lesions including keratoacanthomas (KA) and cuSCC are considered a class effect of BRAFi [Anforth 2012, Chu 2012, Mattei 2012]. These effects, as well as promotion of pre-existing RAS-driven malignancies, may be caused by paradoxical activation of the MAPK pathway downstream of BRAF in wild-type BRAF cells. As MEK inhibition blocks downstream MAPK signaling, it was hypothesized that addition of a MEKi to a BRAFi would abrogate these effects [Su, 2012]. Methods: This 4-part phase I/II study enrolled 365 BRAFV600E/Kmutated MM pts in Parts B-D. In part C, 162 pts (BRAFi and MEKi treatment-naïve, ≥ 18 yrs; ECOG PS <2; RECIST measurable disease) were randomized to D monotherapy 150mg BID (D mono) vs. the combination of D (150 mg BID) and T (1 mg or 2 mg QD). Primary endpoints included safety and efficacy. Occurrence of cuSCC (including KA) across three arms in Part C and secondary malignancies with D+T across all Parts are provided below. Results: The difference in incidence of cuSCC between D mono and the D+T (150/1) was statistically significant, whereas the difference in incidence between D mono and D+T (150/2) was not. The median time to onset of cuSCC was 30 days in D mono compared to 282 and 152 days with D+T (150/1 and 150/2, respectively). Of 365 pts who received D+T, 2 (<1%) cases of new cancers (colorectal and gliobastoma) and 2 (<1%) cases of new primary malignant melanoma were reported. Conclusions: These data support the experimental hypothesis that the occurrence of cuSCC (including KA) can be substantially reduced and delayed by the addition of a MEKi to BRAFi therapy. Clinical trial information: NCT01072175. [Table: see text]

9005 Background: Dual inhibition of the MAP kinase (MAPK) pathway with dabrafenib (D) and trametinib (T) in combination has demonstrated clinical benefit compared to D alone in a randomized Phase II trial in V600 BRAF-mutant MM pts, thus delaying the development of BRAFi resistance. Little is known about the efficacy of D + T after BRAFi resistance has been acquired. This analysis evaluates the ability of D + T combination to treat acquired resistance compared to the D + T combination as first-line treatment. Methods: These data from a phase I/II study include 1. BRAFi-resistant group: pts who received 150/2 D+T in Part B (n=26) and Part C (n=43) following progression on BRAFi monotherapy (mono); 2. BRAFi-naïve group: pts who received initial 150/2 D+T in Part B (n=24) and Part C (n=54). Results: Baseline characteristics (ECOG PS, M staging, LDH) were similar across all groups.In the Part B BRAFi-resistant group, 93% of pts previously received D or vemurafenib and all pts received D prior to D+T in Part C. In BRAFi-resistant group, prior best response of CR/PR (38%, 56%), SD (35%, 27%), PD (27%, 7%) was observed in Parts B and C respectively. In BRAFi-resistant group, the ORR and PFS with D+T was lower than initial D+T in BRAFi-naive group. Median duration of response (DoR) in BRAFi-resistant group cannot be calculated due to small no. of pts responding. Median DoR for BRAFi-naïve pts was 11.3 mo and 10.5 mo in Parts B and C respectively. In Part C, the 12-mo overall survival rates in BRAFi-naïve (150/2) pts was 79% vs 70% for pts initially on D mono, despite 80% pts crossing over to D+T combination. Conclusions: The clinical activity for 150/2 D+T combination is consistently superior in BRAFi-naive group vs BRAFi-resistant group in both Parts B and C. Dual MAPK blockade can delay clinical resistance to BRAF inhibition. However, once BRAFi resistance has occurred, the combination of BRAFi + MEKi is far less effective. Clinical trial information: NCT01072175. [Table: see text]

2579 Background: HA, a glycosaminoglycan, accumulates in ~25% of solid tumors and is associated with poor prognosis. Tumors that accumulate HA develop high interstitial fluid pressure (IFP) and become resistant to chemotherapy. In animal models, PEGPH20 reduced tumor-associated HA and increased efficacy of chemotherapy. Methods: This ongoing phase 1 study was designed to assess safety, tolerability, PK, PD, and the maximum tolerated dose (MTD) of PEGPH20 as a single agent in patients with treatment-refractory solid tumors. IV PEGPH20 was administered in a twice weekly or a once weekly dosing schedule with oral dexamethasone (dex) pre-and post dose. Biomarkers included tumor histochemistry to detect HA depletion, plasma HA catabolites, and DCE-MRI or FDG-PET. Results: Fifteen patients have been enrolled into the study. Dose administration ranged from 0.5 µg/kg to 5 µg/kg. Musculoskeletal events (MSEs) were the most common and dose limiting toxicities. To date, up to 3 µg/kg twice weekly IV infusions of PEGPH20 were well tolerated with manageable Grade 1 MSEs in most patients. MTD has not been reached. Plasma concentrations of PEGPH20 showed dose proportional exposure with a terminal half life of ~2 days. Enzymatic activity of PEGPH20 was reflected by dose-dependent HA catabolites in plasma. Pre- and post-dose tumor biopsies from 2 colon patients demonstrated 23-60% reduction in tumor HA after 4 weeks of dosing. Serial DCE-MRI and FDG-PET demonstrated increased tumor perfusion (Ktrans) and decreased metabolic activity 8 and 24hrs post-PEGPH20 in one patient each. Doses of ≤3 µg/kg were tolerated with intermittent Grade 1-2 MSE. Enrollment at dose levels > 3 µg/kg is ongoing. Conclusions: Repeated IV PEGPH20 infusion resulted in dose-dependent systemic exposure and is tolerated with concomitant dex treatment. HA catabolites in plasma demonstrated the in vivo enzymatic activity of PEGPH20. Reduced HA in tumor biopsies and serial DCE-MRI and FDG-PET images confirmed PD activity. Increased tumor perfusion by PEGPH20 may enhance drug delivery to tumor. Combination studies of PEGPH20 with cytotoxic chemotherapy are planned.

83 Background: PT-112, the first pyrophosphate conjugate in Phase I/II clinical development, induces robust immunogenic cell death and is osteotropic, prompting study in mCRPC during Phase I. We report safety and efficacy findings in the mCRPC sub-population given PT-112 monotherapy (NCT02266745) or in combination with avelumab (“PAVE”) (NCT03409458, ongoing). Methods: Patients (pts) received PT-112 days 1, 8, 15 of a 28d cycle; pts on the PAVE combination also received 800 mg avelumab days 1 and 15; all enrolled during dose escalation or at PT-112 doses previously deemed safe. Pts on therapy (Tx) for ≥2 cycles or who stopped Tx due to progressive disease or treatment-related adverse events (TRAEs) were evaluated for exploratory efficacy. Results: 10 pts on PT-112 (200-420 mg/m2) and 18 pts on PAVE (150-200 mg/m2 PT-112) were evaluable for safety. The most common PT-112 TRAEs were thrombocytopenia (70%, grade (Gr) ≤3) and fatigue (40%, Gr ≤2) with mono-Tx; nausea (50%, Gr ≤2) and fatigue (39%, Gr ≤2) with PAVE. Mono-Tx pts had 6.5 median prior lines of Tx; 2/7 pts with measurable disease (MD) had reductions in target lesions; prostate specific antigen (PSA) declined in 3/10 pts, 1 with ≥50% reduction; and serum alkaline phosphatase (ALP) reductions were seen in 9/10 pts. PAVE pts had 5.5 median prior lines of Tx; radiographic reductions were seen in 2/9 pts with MD; PSA declined in 6/14 pts, 3 with ≥50% decrease, with 1 responder progression free 11.3 months (microsatellite stable). An additional response is ongoing at 4 mos, with 93% PSA decrease and 48% reduction in target lesions (PIK3CBmut & PTEN loss). 13/14 pts with bone metastases had ALP reductions. Pain improvement, opioid cessation and improved performance status were noted in both cohorts. Conclusions: PT-112 was well-tolerated with evidence of efficacy in mCRPC as mono-Tx and in combination with avelumab in heavily pre-treated pts. Bone pain improvement and nearly universal observation of ALP reduction suggest marked therapeutic activity of PT-112 in bone metastases. Serologic / RECIST responses and prolonged disease control in multiple pts substantiate further development of PT-112 in mCRPC. Clinical trial information: NCT02266745, NCT03409458.

2519 Background: PT-112 is a novel platinum-pyrophosphate agent designed to avoid the toxicity and drug resistance mechanisms of conventional chemotherapy. Pre-clinical models show effects on multiple cell signaling components: p16 mediated G1/S cell cycle arrest; modulation of MDM2/p53 expression; extrinsic apoptosis initiation; and immunogenic cell death (ICD) induction. This Phase I first-in-human, multicenter, open label study assesses PT-112’s safety and pharmacokinetic (PK) profile in advanced solid tumor patients (pts), to determine the RP2D and signals of activity. Methods: Pts with advanced solid tumors and acceptable marrow / organ function received PT-112 IV over 1-hr on days 1, 8, and 15 every 4 wks in a 3+3 dose escalation design. Intra-subject escalation was allowed. PK samples from cycles 1-2 were analyzed by ICP-MS and LC-MS/MS. Results: 44 pts have been treated across dose levels (DL) from 12-300mg/m2. Cumulative dosing ranged from 1 to 60 infusions, and cumulative exposure from 96 to 5,244 mg/m2. PK parameters were dose proportional. Target Cmax and AUC levels were achieved, with constant VD. DLTs were observed at 150mg/m2 (G3 pancytopenia); 250mg/m2 (G2 renal injury in a cervical ca pt with hydro-nephrosis); and 300mg/m2 (G3 rash). The most common treatment-related AEs were G1-2 fatigue (26% pts), nausea (23%), vomiting (14%), constipation (12%), and diarrhea (12%). Numerous signals of activity were observed at DLs ≥ 125mg/m2. These include a confirmed PR in a NSCLC pt with 6 prior lines of therapy and no response to TKI inhibition or PD-1 blockade; PFS > 6 months (7-18 months) in 3 pts; metabolic response via PET scan in bone and liver mets (basal cell and pancreatic ca.); biomarker responses in ovarian and prostate ca.; and nodal/metastatic volumetric reduction in 3 pts. Conclusions: PT-112 is a well-tolerated novel agent with a pleiotropic mode of action and feasibility for long-term and combination treatment. Numerous signals of anti-cancer efficacy in heavily pre-treated pts suggest lack of cross-resistance with conventional agents. MTD has not yet been reached. PT-112’s profile makes it an attractive candidate for further development, including in combination with immunotherapy. Clinical trial information: NCT02266745.

9505 Background: D (BRAF inhibitor) + T (MEK inhibitor) combination therapy is associated with rapid clinical responses and has improved clinical outcomes in pts with BRAFV600–mutant MM, but long-term (˃ 3 y) clinical efficacy and safety data are limited. The longest follow-up to date of a randomized trial evaluating D+T at the approved dose (150 mg BID/2 mg QD [150/2]) was of the phase II study BRF113220 (part C; median, 45.6 mo) in which durable outcomes were achieved in some pts with BRAFV600–mutant MM (3-y OS, 38%). Here, we report updated 5-y landmark analyses to further characterize the impact of D+T in MM. Methods: Pts with BRAFV600–mutant mm enrolled in BRF113220 part C (NCT01072175) were randomized 1:1:1 to receive monotherapy D (150 mg BID), D+T (150 mg BID/1 mg QD), or D+T (150/2). Pts who progressed on D alone could cross over to the D+T 150/2 arm. Pt disposition, pt demographics, and 4- and 5-y efficacy and safety were analyzed for both the D-alone and D+T (approved 150/2 dose) arms. Results: This updated analysis represents an additional ≈ 2 y of follow-up (D and D+T arms; n = 54 each). As of 13 Oct 2016, 45 pts (83%) on D alone had crossed over to D+T. 20 pts were ongoing (D, n = 7 [13%]; D+T, n = 13 [24%]); 80% of D pts and 70% of D+T pts had died. D+T OS remained superior to D alone. The 4- and 5-y OS rates with D+T were 30% and 28%, respectively, demonstrating a stabilization of the OS curve. The PFS curve for D+T also remained stable (4- and 5-y: both 13%). Consistent with earlier results, the best OS for pts who received D+T was seen in pts with normal LDH (5-y, 45%) and normal LDH with disease in < 3 organ sites (5-y, 51%). At the 5-y landmark, 1 additional pt who received D+T improved from a partial to a complete response. Additional follow-up revealed no new safety signals with D+T. Detailed analyses of D crossover pts, responders, and post-progression therapy will be presented. Conclusions: This longest follow-up to date of BRAF + MEK inhibitor combination therapy in pts with BRAFV600–mutant mm revealed stable OS and PFS lasting ≥ 5 y with consistent tolerability. These results demonstrate that some pts with mm can achieve durable benefit with D+T therapy. Clinical trial information: NCT01072175.