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3052 TG02, an Oral CDK9-Inhibitor, in Combination with Carfilzomib Demonstrated Objective Responses in Carfilzomib Refractory Multiple Myeloma Patients

Myeloma: Therapy, excluding Transplantation
Program: Oral and Poster Abstracts
Session: 653. Myeloma: Therapy, excluding Transplantation: Poster II
Sunday, December 6, 2015, 6:00 PM-8:00 PM
Hall A, Level 2 (Orange County Convention Center)

Craig C Hofmeister, MD, MPH1, Jesus G. Berdeja, MD2, David H. Vesole, MD, PhD3, Attaya Suvannasankha, MD4*, Tracy Parrott5* and Rafat Abonour, MD6

1Department of Internal Medicine, Division of Hematology, The Ohio State University, Columbus, OH
2Sarah Cannon Research Institute, Nashville, TN
3John Theurer Cancer Center, Hackensack University Medical Center, Hackensack, NJ
4IU Simon Cancer Center, Indiana University, Indianapolis, IN
5Tragara Pharmaceuticals, Carlsbad, CA
6Hematology/Oncology, Indiana University School of Medicine, Indianapolis, IN

Introduction:TG02 is an orally-bioavailable, multikinase inhibitor where the primary mechanism of action is through CDK9-dependent depletion of oncoproteins such as Mcl-1 and MYC.  Safety and efficacy results for multiple myeloma (MM) patients (pts) enrolled in this ongoing phase 1b study are presented. CDK9 inhibition potently suppresses Mcl-1 to induce durable apoptotic responses in lymphoma (Gregory GP, Leukemia, 2015). CDK9 dependence may represent a druggable vulnerability in lymphomas and myelomas with dysregulated MYC expression, although inhibition of both CDK9 and MYC/BRD4 may be required for apoptosis (Lu H et al, Elife, 2015).

 Methods: This open-label Phase 1b study enrolled MM pts that previously received ≥2 lines of therapy. The primary objective was to determine the maximum tolerated dose (MTD) of TG02 in combination with carfilzomib (TG02/ CFZ); key secondary objectives were anti-tumor activity and safety.  TG02 was administered once daily on days 1, 4, 8, 11, 15, 18 of a 28-day schedule (BIW). The TG02 starting dose was 150 mg; TG02 dosing was escalated in 50 mg increments up to 300 mg.  CFZ was dosed according to the Prescribing Information.  Responses were assessed using standard criteria.

 Results: Fourteen pts were enrolled for dose escalation and 10 pts were enrolled for the MTD cohort expansion. Patients were heavily pretreated: median 6 previous treatments [min 3; max 15] and 92% pts received CFZ in a prior regimen. Best response to previous therapy was progressive disease in 46% pts.  The MTD was 250 mg TG02 combined with CFZ.  Two dose-limiting toxicities were observed (including Grade (Gr) 4 sepsis and Gr 4 neutropenia), both on the 300 mg cohort.  The most common drug-related adverse events (AEs) were diarrhea (Gr 1-2: 71% Gr 3: 17%), nausea (Gr 1-2: 79%), vomiting (Gr 1-2: 50%), fatigue (Gr 1-2: 38%, Gr 3: 4%), anorexia (Gr 1: 21%), anemia (Gr 1-2: 4%, Gr 3: 17%) and thrombocytopenia (Gr 3: 8%, Gr 4: 13%). Six patients (25%) discontinued treatment due to an AE.  Serious AEs occurred in 50% pts; only acute renal failure and febrile neutropenia occurred in >1 pt (8% each).  The severity of AEs was similar to single agent TG02. The incidence of diarrhea was increased in the TG02/ CFZ administration (88% vs 67%) but the incidence of other AEs was similar to single agent TG02.  Fourteen pts administered TG02 at the MTD were evaluable for response. The overall response rate (≥PR) was 27%; the clinical benefit rate (≥MR) was 45% (1 very good partial response, 2 partial response and 2 minimal response).  All responders (MR or better) were CFZ-refractory in a previous treatment regimen.  Durable stable disease was observed in 27% pts.

 Conclusions:  The safety profile of TG02 BIW/ CFZ was similar to that of TG02 alone.  The most common drug-related AEs were diarrhea, nausea, and vomiting; grade 4 AEs were infrequent. Additional measures will be taken to improve gastrointestinal tolerability.  Objective responses were observed in CFZ-refractory pts. Enrollment of CFZ-refractory pts administered TG02 on a once-weekly schedule in combination with CFZ is continuing.  Based on promising preclinical data, analysis of Mcl-1 and MYC expression and correlation to clinical outcome will be performed.

Disclosures: Berdeja: Onyx: Research Funding ; Array: Research Funding ; Acetylon: Research Funding ; Celgene: Research Funding ; Curis: Research Funding ; BMS: Research Funding ; Janssen: Research Funding ; Novartis: Research Funding ; MEI: Research Funding ; Takeda: Research Funding ; Abbvie: Research Funding . Abonour: Celgene: Research Funding , Speakers Bureau .

*signifies non-member of ASH