Phase 1b/2 Study of Vipor (Venetoclax, Ibrutinib, Prednisone, Obinutuzumab, and Lenalidomide) in Relapsed/Refractory B-Cell Lymphoma: Safety, Efficacy and Molecular Analysis

Background: Aggressive B-cell non-Hodgkin lymphoma (NHL) can be cured with chemoimmunotherapy; however, those who fail primary therapy and those with indolent NHL are rarely curable. Targeted agents can disrupt key survival pathways in NHL such as regulation of apoptosis (BCL2: venetoclax), B-cell receptor signaling (BTK: ibrutinib), and NF-κB survival pathways (IRF4/SPIB: lenalidomide). These agents are active as monotherapy but fail to induce deep responses and require continuous therapy. Also, genetically defined subtypes of NHL that best respond to these targeted agents are undefined. Synergistic cytotoxicity has been shown with these targeted therapies and corticosteroids in DLBCL cell lines. We hypothesized that combining agents that target multiple survival pathways will leverage efficacy and time-limited, cyclic dosing will limit toxicities.

Methods: Relapsed/refractory (R/R) B-cell NHL pts, excluding MCL and CLL/SLL, with adequate organ function were eligible. A phase I "3+3" design was used to determine the maximum tolerated dose (MTD) of 4 dose-levels (DLs) of dose-escalated venetoclax (200mg, 400mg, 600mg, and 800mg) PO D2-14 (starts cycle 2 for DL1) in combination with fixed-dose ibrutinib 560mg PO D1-14, prednisone 100mg PO D1-7, obinutuzumab 1000mg IV D1-2, and lenalidomide 15mg PO D1-14. A phase II expansion in R/R DLBCL and FL was included at the MTD. Up to 6 cycles of ViPOR every 21-days was given without maintenance. TLS and PCP prophylaxis was given to all pts and VTE prophylaxis and G-CSF use was per investigator discretion. Baseline CT, PET, BM and tumor biopsy was performed with CT scans after cycles 1, 2, 4, and 6 and PET after cycle 6 or at time of suspected CR. Surveillance CT was performed q3m for 1y, q4m x 1y, q6m x 1y, then annually x 2y.

Results: 53 pts were enrolled and treated; 17 in dose-escalation and 36 in dose-expansion. NHL subtypes included DLBCL (23), FL (19), HGBCL "double-hit" (9), and MZL (2). Of 32 aggressive pts, 34% transformed from indolent NHL. Median age was 57y (range 29-83) with stage III/IV disease in 89%, elevated LDH in 68%, and >2 EN sites in 57%. Median prior therapies was 3 (range 1-9) with 45% of pts refractory (i.e. <PR) to last therapy.

A single dose-limiting toxicity (DLT) of G3 intracranial hemorrhage occurred at DL1 with concomitant enoxaparin and ASA. No other DLTs occurred and venetoclax 800mg was used in expansion. Heme AEs (% cycles) were most common and included thrombocytopenia (23%), neutropenia (23%) and anemia (7%). G-CSF was used in 92% of pts and 89% of cycles with only 3 (6%) cases of febrile neutropenia. Non-heme AEs (% pts) were mainly G1-2 and included diarrhea (67%), hypokalemia (56%), nausea (52%), and rash (42%). Most common G3-4 non-heme AEs included hypokalemia (19%), diarrhea (8%), and a.fib/flutter (6%). G4 TLS occurred in 1 pt with HGBCL after the first venetoclax dose and was successfully treated without further TLS upon continued treatment. Dose reductions and delays occurred in 8% and 9% of cycles, respectively.

Of 53 total patients, 51 completed 1C of therapy with restaging CT and tumor reduction occurred in 90% of pts overall (Fig 1A). Of 44 pts who are now off therapy, 43 were evaluable for response with an ORR of 70% and 49% CR, with responses across all DLs and NHL subtypes. In 27 pts with aggressive NHL, ORR was 56% with 37% CR. Based on DLBCL subtype by IHC, ORR and CR rate was 62% (8/13) and 54% (7/13) in non-GCB and 50% (7/14) and 21% (3/14) in GCB DLBCL, respectively. In 16 pts with indolent NHL, ORR was 94% with 69% CR. ORR and CR rate was 52% (11/21) and 29% (6/21) in refractory pts and 86% (19/22) and 68% (15/22) in relapsed pts, respectively. ORR was 40% with 30% CR in 10 patients who failed prior CAR-T and completed ViPOR therapy. With a median potential f/u of 13m, median TTR and DOR was 0.8m and NR, respectively, with 25 (69%) of 36 responses ongoing. 5 pts relapsed after CR, including 2 non-GCB at 3m and 6m, 1 HGBCL at 5m, 1 FL at 6m, and 1 MZL at 16m. Median PFS and OS was 9m and NR, respectively; 20m and NR in indolent NHL, 3m and 13m in GCB, and 7m and 13m in non-GCB DLBCL (Fig 1B).

Conclusions: ViPOR is safe without unexpected toxicities observed. Most common AEs were hematologic with rare febrile neutropenia and no severe infections observed when given with G-CSF prophylaxis. ViPOR induces durable CRs without maintenance therapy, including refractory and post CAR-T pts. Molecular analyses are ongoing and will be presented at the meeting.

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