Updated Results of a Phase II Randomized Study (ROMULUS) of Polatuzumab Vedotin or Pinatuzumab Vedotin Plus Rituximab in Patients with Relapsed/Refractory Non-Hodgkin Lymphoma

Background: Previously reported results from an ongoing study of polatuzumab vedotin (PoV) and pinatuzumab vedotin (PiV), antibody drug conjugates (ADC) containing the anti-mitotic MMAE targeting CD79b (PoV) and CD22 (PiV), showed clinical activity in combination with rituximab (R) in relapsed/refractory (r/r) diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL). Here we report updated results of ADC + R at the RP2D of 2.4 mg/kg and initial results of PoV + R in r/r FL at the PoV dose of 1.8 mg/kg.

Methods: Pts were randomized to receive PoV or PiV + R (ADC 2.4 mg/kg + R 375 mg/m²). In a separate non-randomized cohort (Cohort C), r/r FL pts were treated with PoV (1.8 mg/kg) + R. ADC + R was given every 21 days. Tumor assessments were performed every 3 months.

Results: As of 21 February 2014, 59 pts received PoV + R (39 DLBCL; 20 FL), 63 PiV + R (42 DLBCL; 21 FL); 20 r/r FL pts were treated in Cohort C. Median time of follow-up was 10 mo. for PoV + R, 9 mo. for PiV + R, and 5 mo. for Cohort C. Median prior therapies [DLBCL, 3 (1-10); FL, 2 (1-8)] were balanced among the randomized treatment (tx) arms, median prior therapies in Cohort C was 2 (1-13); overall 44% were R refractory. Median tx cycles in DLBCL: 6 PoV (range 1-16) and 7 PiV (1-15); FL: 10 PoV (3-17), 7 PiV (1-14), and 6 Cohort C (2-10).

Overall safety profiles of both regimens in the randomized arms receiving 2.4 mg/kg ADC were similar. The most common tx-emergent adverse events (AE) ≥25%: fatigue (55%), diarrhea (43%), nausea (37%), peripheral neuropathy (PN) (39%), neutropenia (27%), constipation (26%), sensory PN (25%), and decreased appetite (25%). Grade ≥ 3 AE >3%: neutropenia (24%), diarrhea (6%), dyspnea (5%), febrile neutropenia (4%), hyperglycemia (4%), fatigue (3%), and thrombocytopenia (3%). Serious AEs were reported in 43% and 36% of PiV and PoV treated pts, respectively. Discontinuation of study treatment for AE was reported in 49% and 41% of PiV and PoV treated pts, respectively. Thirty-five pts discontinued treatment due to PN with a median time to discontinuation of 5.6 mo. PN reversibility was observed following treatment interruptions and ADC dose modifications. Two of 9 Grade 5 AEs (sepsis, urosepsis) were attributed to CD22 ADC; no Grade 5 AEs were attributed to CD79b ADC.

In Cohort C the most common tx-emergent AE ≥ 25%: fatigue (55%), nausea (45%), neutropenia (40%), sensory PN (30%), diarrhea (25%), constipation (25%) and pyrexia (25%). Grade ≥ 3 neutropenia was reported in 7 pts; no other Grade ≥ 3 AE was reported in >1 pt. Serious AE were reported in 5 pts. Two pts discontinued study treatment for AE. No Grade 5 AEs were reported.

Overall response rate (ORR), complete (CR) and partial (PR) response rates, n (%) [95% CI], and median PFS in DLBCL (95% CI) are shown in the table. Median PFS in the FL cohorts are not reported due to insufficient follow-up duration.

Pharmacokinetic profiles were similar for both ADCs across DLBCL and FL with no free MMAE accumulation. Pts receiving PoV at 1.8 mg/kg had proportionately lower exposure of antibody conjugated MMAE compared to pts treated at the 2.4 mg/kg dose level.

Conclusions: PoV and PiV + R were generally well-tolerated with similar toxicity profiles. Neutropenia, PN, and diarrhea were the principal toxicities. Similar efficacy was observed with both ADCs in heavily pretreated pts with DLBCL. The higher CR rate with PoV + R compared to PiV + R suggests greater clinical activity in r/r FL. Lower overall response rates were observed in r/r FL pts treated with a lower dose of PoV. Results based on longer follow-up to further assess differences in safety and tolerability between the two PoV doses in r/r FL will be presented. Additional data of pts who received crossover ADC + R treatment following documented disease progression on initial ADC + R treatment will also be presented. Combination studies of PoV + R with chemotherapy and with ADC schedules to reduce PN are ongoing or in planning.