Abstract CT009: Results of a dose- and regimen-finding Phase Ib study of HDM201 in combination with ribociclib in patients with locally advanced or metastatic liposarcoma

Abstract

Background: Well-differentiated/dedifferentiated liposarcoma (WDLPS/DDLPS) is characterized by a consistent coamplification of human double minute 2 homolog (HDM2) and cyclin-dependent kinase 4 (CDK4) which inactivates the tumor suppressor pathways p53 and Rb, respectively. HDM201 is a selective inhibitor of the p53-HDM2 interaction and ribociclib is a CDK4/6 inhibitor. Preclinical studies suggested a synergy in in vitro and in vivo models of WDLPS/DDLPS and both agents have demonstrated single-agent clinical activity in solid tumors. We aim to determine the optimal dose and regimen of HDM201 + ribociclib and to assess the preliminary antitumor activity of this combination in patients (pts) with liposarcoma. Methods: In this multicenter, open-label, Phase Ib ongoing study, pts with locally advanced or metastatic liposarcoma that had unequivocally progressed on, or despite prior systemic therapy were treated orally with HDM201 + ribociclib. Three treatment regimens were explored: Regimen (Reg) 1 (HDM201 + ribociclib daily for the first 2 wks [QD 1st 2 wks] in a 4-wk cycle), Reg 4 (HDM201 every 3 wks + ribociclib QD 1st 2 wks in a 3-wk cycle), and Reg 5 (HDM201 every 4 wks + ribociclib QD 1st 2 wks in a 4-wk cycle). Results: As of Nov 21, 2017, 74 pts received HDM201 + ribociclib (Reg 1 n=26; Reg 4 n=29; Reg 5 n=19); 12 pts (6 each in Reg 4 and 5) were still receiving treatment. Ten pts (Reg 1 n=3; Reg 4 n=6; Reg 5 n=1) discontinued treatment due to adverse events (AEs) and 2 pts (1 each in Reg 4 and 5) died. The most common AE of any grade, regardless of cause, reported across regimens (Reg 1; Reg 4; Reg 5) was nausea (81%; 76%; 63%) which was mainly Grade 1/2 and not dose limiting. Common Grade 3/4 AEs regardless of cause included neutropenia (39%; 52%; 42%), thrombocytopenia (35%; 45%; 42%), anemia (27%; 17%; 21%), leukopenia (27%; 28%; 37%), and lymphopenia (15%; 14%; 21%). Dose-limiting toxicities were reported in 16 pts (2; 9; 5) and all except 1 (prolonged QT) were hematologic (including neutropenia [n=5], thrombocytopenia [n=4], febrile neutropenia, and anemia [n=2 each]). Partial responses were observed in 3 (4%) pts (2 in Reg 4; 1 in Reg 5). Stable disease was achieved by 36 (49%) pts (11 in Reg 1; 16 in Reg 4; 9 in Reg 5). The median progression-free survival (PFS) was 2.7 mo (95% confidence interval [CI]: 1.9-8.2 mo) in Reg 1, 4.8 mo (95% CI: 3.9 mo-not reached) in Reg 4, and 2.1 mo (95% CI: 1.4 mo-not reached) in Reg 5. Conclusions: HDM201 + ribociclib demonstrated a manageable safety profile and preliminary efficacy in pts with locally advanced or metastatic WDLPS/DDLPS, with hematologic toxicities being dose limiting. The median PFS in Reg 4 compares favorably with single-agent CDK4 inhibitors and, alongside a tolerable safety profile, suggests further exploration of this regimen may be warranted in Phase II studies of HDM201 + ribociclib in this patient population. Citation Format: Albiruni Abdul Razak, Sebastian Bauer, Jean-Yves Blay, Richard Quek, Cristina Suárez, Chia-Chi Lin, Marie L. Hütter-Krönke, Ricardo Cubedo, Stephane Ferretti, Christophe Meille, Ensar Halilovic, Giorgia Clementi, Maria Santos-Rosa, Nelson Guerreiro, Astrid Jullion, Claire Fabre, Antoine Italiano. Results of a dose- and regimen-finding Phase Ib study of HDM201 in combination with ribociclib in patients with locally advanced or metastatic liposarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT009.

Recent advances in the understanding and management of liposarcoma

“…A phase II study investigating the more potent inhibitor abemaciclib is underway in patients with pretreated or untreated DDLPS, with a preliminary analysis showing a prolonged median PFS of 30.4 weeks 32 . Ribociclib is also in phase II clinical trials in combination with the mTOR inhibitor everolimus 33 and MDM2 inhibitor HDM201 34 , 35 , with results pending at this time.…”

Genomic-guided precision therapy for soft tissue sarcoma

“…In a dose-finding phase Ib study of HDM201 (an MDM2 inhibitor) in combination with ribociclib (a CDK4/6 inhibitor) in patients with WDLPS/DDLPS, partial responses were observed in 4% of the patients, and stable disease was achieved by 49% of patients. Again, the most common side effect is haematologic including neutropenia, thrombocytopenia and anaemia 87…”

Next frontiers in systemic therapy for soft tissue sarcoma

“…However, because stabilizing p53 through mdm2 inhibition causes cell apoptosis, the common class effect toxicity for mdm2 inhibitors is bone marrow toxicities. Grade 3 or 4 neutropenia or even prolonged thrombocytopenia has been experienced by 30% or higher of patients (30)(31)(32). Multiple different drugs dosage schedules are currently explored to find the best schedule.…”