FDA Approves Antibody-Drug Conjugate POLIVY® for Diffuse Large B-Cell Lymphoma

SUMMARY: The FDA on June 10, 2019, granted accelerated approval to POLIVY® (Polatuzumab vedotin-piiq), a CD79b-directed Antibody-Drug Conjugate, indicated in combination with Bendamustine and a Rituximab product, for adult patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma (DLBCL), Not Otherwise Specified, after at least two prior therapies.

The American Cancer Society estimates that in 2019, about 74,200 people will be diagnosed with Non Hodgkin Lymphoma (NHL) in the United States and about 19,970 individuals will die of this disease. Diffuse Large B-Cell Lymphoma (DLBCL) is the most common of the aggressive Non-Hodgkin lymphoma’s in the United States, and the incidence has steadily increased 3-4% each year. More than half of patients are 65 or older at the time of diagnosis and the incidence is likely to increase with the aging of the American population. The etiology of Diffuse Large B-Cell Lymphoma is unknown. Contributing risk factors include immunosuppression (AIDS, transplantation setting, autoimmune diseases), UltraViolet radiation, pesticides, hair dyes, and diet. DLBCL is a neoplasm of large B cells and the most common chromosome abnormality involves alterations of the BCL-6 gene at the 3q27 locus, which is critical for germinal center formation. Two major molecular subtypes of DLBCL arising from different genetic mechanisms have been identified, using gene expression profiling: Germinal Center B-cell-like (GCB) and Activated B-Cell-like (ABC). Patients in the GCB subgroup have a higher five year survival rate, independent of clinical IPI (International Prognostic Index) risk score, whereas patients in the ABC subgroup have a significantly worse outcome. Regardless, R-CHOP regimen (RITUXAN®-Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone), given every 21 days, for 6 cycles, delivered with curative intent, is the current standard of care for patients of all ages, with newly diagnosed DLBCL, regardless of molecular subtype. Approximately 30-40% of patients experience disease progression or relapse, during the first 2 years and attempts to improve on R-CHOP regimen have not been successful. Maintenance treatment strategy following R-CHOP, to better control the disease, delay disease progression and improve long term survival, have included Autologous Stem Cell Transplantation, maintenance treatment with agents such as oral protein kinase inhibitor Enzastaurin and Everolimus. Outcomes for transplant-ineligible patients with Relapsed/Refractory DLBCL patients remain poor.

CD79b is a B-cell specific surface protein, which is a component of the B-cell receptor. POLIVY® is a CD79b-directed Antibody-Drug Conjugate (ADC) with activity against dividing B cells. It consists of three components: 1) the humanized ImmunoGlobulin G1 (IgG1) monoclonal antibody specific for human CD79b; 2) the small molecule anti-mitotic agent MMAE (monomethyl auristatin E) and 3) a protease-cleavable linker that covalently attaches MMAE to the Polatuzumab antibody. Upon binding to CD79b, POLIVY® is internalized, and the linker is cleaved by lysosomal proteases thus enabling intracellular delivery of MMAE. MMAE then binds to microtubules and kills dividing cells by inhibiting cell division and inducing apoptosis.

The present FDA approval was based on an open-label, randomized, multicenter, Phase II clinical trial (Study GO29365) which included a cohort of 80 transplant-ineligible patients with Relapsed or Refractory DLBCL. Patients who had received at least one prior regimen were randomized (1:1) to receive either POLIVY® in combination with Bendamustine and RITUXAN® (Rituximab) or GAZYVA® (Obinutuzumab) – (P+BR) or BR alone, every 21 days for up to 6 cycles. RITUXAN® or GAZYVA® were administered on day 1 of each cycle at 375 mg/m2 intravenously IV or 1000 mg IV respectively, POLIVY® 1.8 mg/kg IV, was given on day 2 of cycle 1 and on day 1 of subsequent cycles and Bendamustine 90 mg/m2 IV was administered on days 2 and 3 of cycle 1 and on days 1 and 2 of subsequent cycles. The median age was 68 years.

The Primary aim of this study was to assess the efficacy of P+BR versus BR at end of treatment, by an Independent Review Committee (IRC). Responses were assessed using the modified Lugano Classification, and Complete Response (CR) required Positron Emission Tomography (PET) negativity and negative bone marrow biopsy, if positive or unknown at the time of screening. Other end points included Duration of Response (DoR), Progression Free Survival (PFS) and Overall Survival (OS). Efficacy was also evaluated based on Cell of Origin – Activated B-cell-like (ABC), Germinal B-cell-like (GCB), as well as MYC/BCL2 double expression. The median follow up for this cohort of patients was 22.3 months.

The combination of POLIVY® plus BR (P+BR) showed significantly higher PET-CR rates vs BR alone (40% vs 18%; P=0.026). The Objective Response Rate (ORR) was 45% vs 18% with a significantly longer DoR of 10.3 months vs 4.1 months (HR=0.44; P=0.032), favoring P+BR regimen. Among those who achieved Partial or Complete Response to P+BR, 64% had response durations of at least six months and 48% had response durations of at least 12 months. The PFS was 7.6 months vs 2 months (HR=0.34; P<0.0001) and OS was 12.4 months vs 4.7 months (HR=0.42; P=0.0023), all favoring P+BR over BR. For ABC patients the median PFS with P+BR was 10.5 months vs 2.5 months for BR and the median OS was 13.9 vs 4.3 months, respectively. For GCB patients, median PFS with P+BR was 4.7 vs 1.5 months for BR and the median OS was 9.3 vs 3.2 months, respectively. Among those with MYC/BCL2 Double Expression, the median PFS was 7.0 months vs 0.7 months with P+BR, and median OS was 12.9 vs 3.8 months compared to BR. For non-Double Expression group of patients, the median PFS was 6.3 months vs 2.5 months and median OS was 10.5 vs 3.8 months with P+BR vs BR, respectively.

It was concluded that a combination of POLIVY® given along with Bendamustine and RITUXAN® or GAZYVA® provides a promising treatment option for Relapsed/Refractory DLBCL patients who are transplant ineligible, with durables responses in some patients of over 20 months and median OS surpassing 12 months. Polatuzumab vedotin (Pola) plus bendamustine (B) with rituximab (R) or obinutuzumab (G) in relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL): updated results of a phase (Ph) Ib/II study. Sehn LH, Herrera AF, Matasar MJ, et al. Blood. 2018;132:1683.