Combination of Idasanutlin, Venetoclax and Obinutuzumab in Patients with Relapsed or Refractory (R/R) Non-Hodgkin Lymphoma (NHL): Results from a Phase I/II Study

Background

Follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) are the most common indolent and aggressive B-cell lymphomas, respectively. Although the combination of anti-CD20 therapies rituximab (R) or obinutuzumab (G) with chemotherapy has led to improved patient (pt) outcomes, R/R disease remains a challenge, with a high unmet need. The potent and selective MDM2 antagonist idasanutlin (idasa) activates the p53 pathway, leading to anti-tumor activity. The BCL-2 inhibitor venetoclax (ven) has shown clinical activity in hematologic diseases including R/R NHL. In a Phase Ib/II study (NCT02624986), idasa could be safely combined in a doublet treatment (tx) regimen with R or G in R/R FL or DLBCL pts. Here we report the tolerability, safety and preliminary efficacy of the triplet tx regimen of idasa plus ven and G in R/R NHL pts.

Methods

BH39147 (NCT03135262) was an open-label, multicenter, non-randomized, Phase Ib/II study with a dose-escalation phase followed by an expansion phase. The dose-escalation phase evaluated idasa and ven combined with G in all pts (FL and DLBCL) until the maximum tolerated dose (MTD) was reached. Idasa and ven dose escalations started at 100 and 200 mg PO QD, respectively, on days 1-5 of each 28-day cycle (safety cohort); in subsequent cohorts, ven was given on days 1-10 of each cycle. G was given at a fixed dose of 1000 mg IV on days 1, 8 and 15 of cycle 1 and day 1 of subsequent cycles. Pts received 6 cycles of induction tx. The primary objective of the dose-escalation phase was to determine recommended Phase II doses for idasa and ven in combination with G. Efficacy objectives included evaluating the complete response (CR) rate at the end of induction (EOI) per investigator based on PET-CT. The trial was stopped prior to initiation of the expansion phase; results are presented for the dose-escalation cohorts evaluating idasa plus ven and G.

Results

Of the 29 pts enrolled, 14 each had a diagnosis of FL or DLBCL at study entry, and 1 had an unknown diagnosis at study entry that was later confirmed as FL. The median age was 70 y (range, 25-82), 58.6% of pts were male, and 67.9% had an ECOG PS of 1 or 2. The majority of pts had advanced-stage disease at enrollment, with 58.6% having received ≥ 3 lines of prior anti-lymphoma therapy; 17.2% and 24.1% of pts had received 1 and 2 prior lines of tx, respectively. Median (range) tx durations during induction were 1.3 mo (0-6) for idasa, 1.5 mo (0-7) for ven and 1.5 mo (0-6) for G; post-induction median (range) tx durations (n = 4) were 3.8 mo (0-4), 3.8 mo (0-4) and 8.4 mo (0-11), respectively.

The safety-evaluable population was composed of 29 pts. Grade 3/4 adverse events (AEs) occurred in 86.2% of pts, with neutropenia (79.3%), thrombocytopenia (62.1%), leukopenia (27.6%) and anemia (20.7%) as the most common. No Grade 5 AEs were reported. Serious AEs occurred in 48.3% of pts and were most commonly neutropenia (10.3%). AEs led to treatment discontinuation in 41.4% of pts, with thrombocytopenia (17.2%) and neutropenia (13.8%) being the most common. AEs related to idasa, ven and G were reported in 86.2%, 89.7% and 79.3% of pts, respectively. Dose-limiting toxicities were reported in 4 pts (13.8%): neutropenia (n = 3; 10.3%), hyperbilirubinemia (n = 1; 3.4%) and transaminitis (n = 1; 3.4%). The MTD for idasa was determined to be 150 mg in combination with 200-mg ven and G and 100 mg in combination with 400-mg ven and G.

Preliminary efficacy data are shown in the table. Among all pts, 20.7% (FL, n = 5; DLBCL, n = 1) had a CR at EOI per investigator (PET-CT) based on modified Lugano 2014 criteria. Per investigator based on Lugano 2014 criteria, the CR rate at EOI (CT) was 13.8% (FL, n = 3; DLBCL, n = 1), and the complete metabolic response rate at EOI (PET-CT) was 24.1% (FL, n = 6; DLBCL, n = 1).

Conclusions

This study successfully showed the combinability of idasa and ven with an anti-CD20 agent. MTDs were determined for idasa and ven in combination with G in FL and DLBCL pts. No new safety signals related to any of the study drugs were identified, and the observed safety profiles were consistent with those of each individual study drug. While the combination is feasible and promising, other agents and approaches in the field make this combination less likely to proceed further. As a consequence, this trial has been discontinued following the dose-escalation/proof-of-concept phase to focus on new tx combinations.

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