anti-CD79b Antibody-drug Conjugate Research Articles

Identification of unique molecular heterogeneity of human CD79, the signaling component of the human B cell antigen receptor (BCR), and synergistic potentiation of the CD79-targeted therapy of B cell tumors by co-targeting of CD79a and CD79b

We identified unique molecular heterogeneity of CD79 of human B cell antigen receptor (BCR) that may open a new approach to the ongoing CD79b-targeted therapy of B cell tumors. The primary purpose of the present study is to gain new information valuable for the enhanced CD79-targeted therapy. The molecular heterogeneity of CD79 was identified by sequential immunoprecipitation of BCR by use of anti-CD79b monoclonal antibody (mAb) SN8 and anti-CD79a mAb SN8b. SN8 is the antibody component of polatuzumab vedotin, an anti-CD79b antibody drug conjugate, that has been widely used for therapy of diffuse large B-cell lymphoma (DLBCL). The sequential immunoprecipitation shows that anti-CD79b mAb will be able to react only with a subgroup of CD79 molecules while anti-CD79a mAb will react with another subgroup of CD79 molecules; CD79 is a disulfide-linked heterodimer of CD79a and CD79b. Therapeutic study of SCID mice bearing human B-cell tumor shows synergistic potentiation by co-targeting CD79b and CD79a. Furthermore, simultaneous targeting of PD-1 strongly potentiates CD79a/CD79b-targeted therapy of B cell tumors. Flow cytometry analyses of CD79a/CD79b on malignant B cells of patients may provide a method for selection of the candidate patients for the CD79a/CD79b dual targeting therapy.

Mosunetuzumab with polatuzumab vedotin in relapsed or refractory aggressive large B cell lymphoma: a phase 1b/2 trial

Relapsed/refractory aggressive large B cell lymphoma (LBCL) remains an area of unmet need. Here we report the primary analysis of a phase 1b/2 trial of outpatient mosunetuzumab (a CD20xCD3 T-cell-engaging bispecific antibody) plus polatuzumab vedotin (an anti-CD79B antibody–drug conjugate) in relapsed/refractory LBCL. The phase 2 component is a single arm of an ongoing multi-arm trial. The primary endpoint during dose expansion was independent review committee (IRC)-assessed best overall response rate. Secondary endpoints included investigator-assessed overall response rate, complete response, duration of response, progression-free survival and overall survival. At data cutoff, 120 patients were enrolled (22 dose escalation, 98 dose expansion). The primary endpoint was met during dose expansion, with IRC-assessed best overall response rate and complete response rates of 59.2% (58/98; 95% confidence interval (CI): 48.8–69.0) and 45.9% (45/98; 95% CI: 35.8–56.3), respectively (median follow-up, 23.9 months). Median duration of complete was not reached (95% CI: 20.5–not estimable (NE)). Median progression-free survival was 11.4 months (95% CI: 6.2–18.7). Median overall survival was 23.3 months (95% CI: 14.8–NE). Across dose escalation and expansion, the most common grade 3 or higher adverse events were neutropenia (25.0%, 30/120) and fatigue (6.7%, 8/120). Any-grade cytokine release syndrome occurred in 16.7% of patients. These data demonstrate that mosunetuzumab plus polatuzumab vedotin has a favorable safety profile with highly durable responses suitable as second-line therapy in transplant-ineligible relapsed/refractory LBCL. ClinicalTrials.gov identifier: NCT03671018.

Real Event Analysis of the Efficacy and Safety of Polatuzumab Vedotin Combination Regimen in Patients with Relapsed/Refractory Diffuse Large B-Cell Lymphoma

Abstract： Objective Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodges lymphoma (NHL) subtype, although R⁃CHOP treatment cured about 60% of patients. However, 40%-45% of patients do not respond to first-line therapy or relapse after an initial response, and this segment of patients has a poor prognosis. Therefore, the use of targeted drugs and the exploration of drug combination schemes are particularly important, among them, anti-CD79B antibody-drug conjugate (ADC) polatuzumab vedotin (Pola) combined with Bendamustine-Rituximab (BR) and Pola combined with R-CHOP are promising therapeutic options. To analyze the efficacy and safety of Pola combined with BR and Pola combined with R-CHOP in the treatment of relapsed/refractory DLBCL (R/R DLBCL). Methods The single-arm, Phase II clinical study commenced at our center in May 2023. Eligible patients were R/R DLBCL patients with Ann Arbor stages 3-4, ages 36 to 88 years, who had received at least one previous standard chemotherapy regimen. The clinical data of 17 patients enrolled in our center from May 2023 to August 2023 were retrospectively analyzed, including 10 males and 7 females. The median age was 69 (ranged 36-88) years. 12 patients were treated with Pola-BR and 5 with Pola-R-CHOP, the clinical characteristics, medication regimen, efficacy and occurrence of adverse reactions were analyzed. To explore the causes of adverse reactions between the Polar-BR group and the Polar-R-CHOP group. Results Data as of August 1, 2023, in the efficacy evaluation of 17 patients, the overall response rate (OR) was 71% (12/17) and the complete response (CR) rate was 53% (9/17). Progressive free survival (PFS), median follow-up of 45 days, with 3 cases (12%) experiencing disease progression. Compared with the Pola-BR group, the Pola-RCHOP group had a lower incidence of adverse reactions. The main adverse event was a pulmonary infection, of which 33% (4/12) were in the Polar-BR group and 25% (1/5) were in the Polar-R-CHOP group, and no severe pneumonia occurred in either group. Conclusion Compared with the traditional R-CHOP regimen, Polar+BR/RCHOP has better therapeutic effect and a better application prospects for R/R DLBCL patients.

POLATUZUMAB VEDOTIN IN RELAPSED OR REFRACTORY DIFFUSE LARGE B‐CELL LYMPHOMA PATIENTS: A MATCHED‐CONTROL ANALYSIS FROM THE THAI LYMPHOMA STUDY GROUP (TLSG)

Treatments of patients with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) represent an unmet clinical need. Polatuzumab vedotin (Pola), an anti-CD79b antibody-drug-conjugate (ADC), combined with bendamustine-rituximab (BR), has recently been approved for these patients. However, there were limited data on real-life studies in R/R DLBCL, especially in Thailand. R/R DLBCL patients who received Pola-based regimens as a salvage treatment between 1 April 2021 and 30 March 2022 from the nationwide multi-center in Thailand were included in determining efficacy and safety in the real-world setting. Age, sex, and prior treatments-matched controls were selected from the database of the Thai lymphoma registry. The Pola group and historical control R/R DLBCL patients were compared. Thirty-five patients who received Pola-based treatment (Pola-BR 54.3% and Pola-R 45.7%) were included. The median age was 66 years (IQR 58–79), and the median number of prior treatments was 2 (range 1–4). The overall response rate (ORR) was 62.8%, with complete remission and partial remission of 17.1% and 45.7%. With a median follow-up of 11.8 months, the median progression-free survival (PFS) and overall survival (OS) were 10.6 months and 12.8 months, respectively. Grade 3–4 adverse events (AEs) were mainly hematological: anemia (8.6%), thrombocytopenia (5.7%), neutropenia (22.5%), and febrile neutropenia (8.6%). Compared with 180 matched patients who received non-pola-based therapy, there was a significantly higher ORR in Pola-based salvage treatments (62.8% vs. 33.3%, hazard ratio [HR] 3.52, 95% confidence interval [CI] 1.39-8.95, p < 0.01). The survival outcomes were also significantly superior in the Pola group: the median PFS 10.6 versus 4.2 months (HR 0.49; 95% CI, 0.29-0.85; p = 0.015), median OS 12.8 versus 7.5 months (HR 0.53; 95% CI, 0.34-0.84; p = 0.017). The use of Polatuzumab vedotin combination as a salvage treatment in R/R DLBCL demonstrated promising results with tolerable toxicities in the real-world setting. Keywords: aggressive B-cell non-Hodgkin lymphoma, chemotherapy, immunotherapy No conflicts of interests pertinent to the abstract.

Outcomes of polatuzumab vedotin-containing regimens in real-world setting of relapsed and or refractory diffuse large B-cell lymphoma patients: a matched-control analysis from the Thai Lymphoma Study Group (TLSG).

Relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) is a challenging condition to treat, and there is an unmet clinical need for effective therapies. Recently, polatuzumab vedotin (Pola), an anti-CD79b antibody-drug-conjugate (ADC), combined with bendamustine-rituximab (BR), has been approved for R/R DLBCL patients. However, real-world data on Pola-based regimens in R/R DLBCL patients, especially in Thailand, are limited. This study aimed to evaluate the efficacy and safety of Pola-based salvage treatment in R/R DLBCL patients in Thailand. Thirty-five patients who received Pola-based treatment were included in the study, and their data were compared to 180 matched patients who received non-Pola-based therapy. The overall response rate (ORR) in the Pola group was 62.8%, with complete remission and partial remission rates of 17.1% and 45.7%, respectively. The median progression-free survival (PFS) and overall survival (OS) were 10.6months and 12.8months, respectively. The study found a significantly higher ORR in Pola-based salvage treatments compared to non-Pola-based therapy (62.8% vs. 33.3%). The survival outcomes were also significantly superior in the Pola group, with longer median PFS and OS than the control group. Grades 3-4 adverse events (AEs) were mainly hematological, and they were tolerable. In conclusion, this study provides real-world evidence of the efficacy and safety of Pola-based salvage treatment in R/R DLBCL patients in Thailand. The results of this study are promising and suggest that Pola-based salvage treatment could be a viable option for R/R DLBCL patients who have limited treatment options.

Mosunetuzumab with Polatuzumab Vedotin Is Effective and Has a Manageable Safety Profile in Patients Aged

Background: Treatment decision-making for elderly DLBCL patients (pts) is challenging. Advancing age is associated with an increase in the incidence of comorbidity and vulnerability to treatment-related toxicities (Thieblemont & Coiffier. J Clin Oncol 2007). Mosunetuzumab (M) is a CD20xCD3 T-cell engaging bispecific monoclonal antibody (Ab) that redirects T cells to eliminate malignant B cells. The Phase Ib/II GO40516 study (NCT03671018) is evaluating M in combination with the anti-CD79b antibody-drug conjugate polatuzumab vedotin (Pola; M-Pola) in pts with B-cell non-Hodgkin lymphoma (B-NHL). In the ongoing Phase II part of the study, M-Pola showed an acceptable safety profile with promising activity in pts with R/R B-NHL (Budde et al. ASH 2021). Here, we present a subgroup analysis of the efficacy and safety of M-Pola in pts aged <65 and ≥65 years with R/R aggressive B-NHL from the Phase Ib dose-escalation and Phase II dose-expansion cohorts. Methods: All pts in this analysis had DLBCL (including transformed follicular lymphoma and follicular lymphoma grade [Gr] IIIB), an Eastern Cooperative Oncology Group performance status (ECOG PS) 0-2, and ≥1 prior line of therapy, including an anti-CD20 Ab. Treatment cycles were 21 days. Pola (1.8mg/kg intravenous [IV] infusion) was given on Day (D)1 of Cycle (C)1-6. M (IV infusion) was given with step-up dosing during C1 to mitigate cytokine release syndrome (CRS), and the recommended Phase II dose was used in the Phase II dose-expansion cohort (1mg on C1D1, 2mg on C1D8, 60mg on C1D15 and C2D1, and 30mg on D1 of C3-8). Pts with stable disease or a partial response at the end of C8 could continue M for a total of 17 cycles, while pts with a complete response (CR) discontinued M after C8. In the Phase II expansion cohort, mandatory hospitalization was not required for M administration. Response was assessed by investigators using Lugano 2014 criteria (Cheson et al. J Clin Oncol 2014). CRS events were reported using American Society for Transplantation and Cellular Therapy criteria (Lee et al. Biol Blood Marrow Transplant 2019). Results: As of March 15, 2021, with a median follow-up of 5.3 months (range: 0.7-23.7 months), 60 pts with R/R DLBCL had received M-Pola: 24 (40%) were aged <65 years and 36 (60%) were aged ≥65 years. At study entry, for pts aged ≥65 years, the median age was 73 years (range: 65-83), 53% had ECOG PS 1 and 8% had PS 2, 50% had International Prognostic Index 3-5, 81% had Ann Arbor stage III/IV disease, and 81% and 72% were refractory to a prior anti-CD20 Ab and to last prior therapy, respectively. There were more pts <65 years than pts ≥65 years with high lactate dehydrogenase (LDH; 63% vs 44%, respectively), with ≥3 prior lines of therapy (67% vs 56%), and refractory to CAR T-cell therapy (38% vs 25%; Table). Compared with younger pts, those aged ≥65 years had a numerically higher ORR (72% [95% CI: 55-86] vs 54% [95% CI: 33-75]) and CR rate (56% [95% CI: 38-72] vs 38% [95% CI: 19-59]). The rate of Gr 3-4 adverse events (AEs) was lower in pts ≥65 years than in those <65 years (39% vs 58%, respectively), with fewer neutropenia events occurring (14% vs 33%); the rate of serious AEs of any Gr was similar (39% vs 33%). Five pts ≥65 years discontinued M and/or Pola due to treatment-related AEs compared with one pt <65 years. The rate of CRS was comparable in pts aged ≥65 and <65 years (17% vs 21%), all CRS events were low-Gr (≥65 vs <65 years: Gr 1, 14% vs 21%; Gr 2, 3% vs 0%), and all CRS events resolved. Rates of serious AEs of infection were comparable in pts aged ≥65 and <65 years (11% vs 17%, respectively). Rates of peripheral neuropathy were 42% in pts aged ≥65 years vs 21% in pts aged <65 years, with most events Gr1-2 (≥65 vs <65 years: 1 vs 2 Gr 3 events). After the first M-Pola dose, pharmacodynamic changes in interferon-α and T-cell activation in peripheral blood were similar across age groups. Conclusions: M-Pola is effective and has a manageable safety profile in pts with heavily pretreated DLBCL, including older pts who may have more comorbidities and fewer treatment options, such as those who are poor candidates for CAR T-cell therapy. Numerically higher ORR and CR rates were seen in pts aged ≥65 years, although longer follow-up is required. Comparable rates of CRS and serious AEs were observed across age groups. Enrollment in the Phase II study with no mandatory hospitalization is ongoing. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

DLBCL 1L-What to Expect beyond R-CHOP?

Simple SummaryDiffuse large B-cell lymphoma (DLBCL) is the most common aggressive non-Hodgkin’s lymphoma. About two-thirds of patients are cured by the first-line (1L) standard of care (SOC), the R-CHOP (Rituximab, Cyclophosphamide, Doxorubicin, Vincristine and Prednisolone) immunochemotherapy protocol. The profound molecular heterogeneity of DLBCL is the underlying reason why many patients, despite improved next-line options, eventually succumb to the disease. Hence, enhancing the efficacy of 1L treatment is critical for improving long-term outcomes in DLBCL. A plethora of novel treatment options with potential in later lines is currently under evaluation in 1L settings. We summarize here the established and emerging strategies for newly diagnosed DLBCL and emphasize the need for individualized treatment decisions.The R-CHOP immunochemotherapy protocol has been the first-line (1L) standard of care (SOC) for diffuse large B-cell lymphoma (DLBCL) patients for decades and is curative in approximately two-thirds of patients. Numerous randomized phase III trials, most of them in an “R-CHOP ± X” design, failed to further improve outcomes. This was mainly due to increased toxicity, the large proportion of patients not in need of more than R-CHOP, and the extensive molecular heterogeneity of the disease, raising the bar for “one-size-fits-all” concepts. Recently, an R-CHP regimen extended by the anti-CD79b antibody–drug conjugate (ADC) Polatuzumab Vedotin proved superior to R-CHOP in terms of progression-free survival (PFS) in the POLARIX phase III trial. Moreover, a number of targeted agents, especially the Bruton’s tyrosine kinase (BTK) inhibitor Ibrutinib, seem to have activity in certain patient subsets in 1L and are currently being tested in front-line regimens. Chimeric antigen receptor (CAR) T-cells, achieving remarkable results in ≥3L scenarios, are being exploited in earlier lines of therapy, while T-cell-engaging bispecific antibodies emerge as conceptual competitors of CAR T-cells. Hence, we present here the findings and lessons learnt from phase III 1L trials and piloting phase II studies in relapsed/refractory (R/R) and 1L settings, and survey chemotherapy-free regimens with respect to their efficacy and future potential in 1L. Novel agents and their mode of action will be discussed in light of the molecular landscape of DLBCL and personalized 1L perspectives for the challenging patient population not cured by the SOC.

ABCL-351: Promising Tolerability and Efficacy Results from Dose-Escalation in an Ongoing Phase Ib/II Study of Mosunetuzumab with Polatuzumab Vedotin (Pola) in Patients with Relapsed/Refractory (R/R) B-Cell Non-Hodgkin Lymphoma (B-NHL)

<h3>Context</h3> Mosunetuzumab (Mosun), a full-length, humanized, IgG1 CD20xCD3 bispecific antibody, showed promising efficacy/safety for R/R B-NHL (NCT02500407; Assouline, <i>et al.</i> ASH 2020). Mosun combined with the anti-CD79b antibody-drug conjugate Pola showed synergistic anti-lymphoma activity in a mouse xenograft model, supporting the Phase Ib/II, open-label, multicenter trial of Mosun-Pola for R/R B-NHL (GO40516, NCT03671018). <h3>Objective</h3> To present early clinical data from the Phase Ib cohort of GO40516. <h3>Methods</h3> Patients with R/R follicular lymphoma (FL, grade 1–3a) or aggressive NHL (aNHL), including <i>de novo</i> diffuse large B-cell lymphoma (DLBCL), transformed FL (trFL), and grade 3b FL (FL3b), received Cycle (C)1 step-up doses of Mosun on Day (D)1 (1 mg) and D8 (2 mg), and target dose on C1D15, continuing from C2D1. Mosun was given every 21 days for eight cycles, continuing for ≤17 cycles. Pola (1.8 mg/kg) was administered with Mosun on D1 of six cycles. <h3>Results</h3> As of November 17, 2020, 22 patients received Mosun-Pola (Mosun target doses: 9 mg, n=7; 20 mg, n=3; 40 mg, n=6; 60 mg [D1 dose 30 mg from C3 onward], n=6). Patients had DLBCL (n=12), FL (n=3), FL3b (n=3), and trFL (n=4). Median age: 70 (38–81) years; median 3 (1–10) prior lines of therapy; prior chimeric antigen receptor T-cell (CAR-T) therapy (n=7; 32%). Median follow-up duration: 9.6 (0.7–23.7) months. Most frequent treatment-related adverse events (AEs): neutropenia (45.4%), fatigue, nausea, and diarrhea (all 36.4%). Cytokine release syndrome was observed in two patients (9.1%; both grade 1 [Lee, <i>et al.</i> Biol Blood Marrow Transplant 2019]). One dose-limiting toxicity (grade 3 new-onset atrial fibrillation) was observed in the 40 mg cohort; maximum tolerated dose not exceeded. Most common grade ≥3 AE: neutropenia (n=8; 36.4%). Two (9.3%) grade 5 AEs occurred (sudden cardiac death [n=1]); respiratory failure [n=1]); neither was deemed treatment-related. Complete responses were achieved with Mosun-Pola in patients with R/R aNHL (n=9; 47.4%), prior CAR-T therapy (n=2; 28.6%) and FL (n=3; 100%). <h3>Conclusions</h3> These data indicate that Mosun-Pola has an acceptable safety profile and shows promising efficacy in patients with predominantly aggressive R/R NHL. The Phase II expansion cohort in patients with R/R DLBCL is ongoing, with no requirement for mandatory hospitalization.

Promising tolerability and efficacy results from dose-escalation in an ongoing phase Ib/II study of mosunetuzumab (M) with polatuzumab vedotin (Pola) in patients (pts) with relapsed/refractory (R/R) B-cell non-Hodgkin’s lymphoma (B-NHL).

7520 Background: Mosunetuzumab (M), a full-length, humanized, IgG1 bispecific antibody targeting CD20 and CD3, has shown promising efficacy and safety as monotherapy for R/R B-NHL (NCT02500407; Assouline, et al. ASH 2020). The combination of M with the anti-CD79b antibody-drug conjugate, Pola, showed synergistic anti-lymphoma activity in a mouse xenograft model. These data supported a Phase Ib/II, open-label, multicenter trial of M-Pola for R/R B-NHL (GO40516, NCT03671018). Here we present early clinical data from the Phase Ib cohort. Methods: Pts with R/R follicular lymphoma (FL, grade [Gr] 1–3a) or aggressive NHL (aNHL), including de novo diffuse large B-cell lymphoma (DLBCL), transformed FL (trFL) and FL Gr 3b (FL3b), received Cycle (C) 1 step-up doses of M on Day (D) 1 (1mg) and D8 (2mg), the target dose on C1D15, then continued at the target dose on C2D1 onwards. M was given every 21 days for eight cycles (or 17 cycles if stable disease or a partial response after C8). Pola (1.8mg/kg) was given with M on D1 of each cycle for six cycles. Results: As of November 17, 2020, 22 pts had received M-Pola (M target doses: 9mg, n=7; 20mg, n=3; 40mg, n=6; 60mg [with D1 dose of 30mg from C3 onwards], n=6). Pts had DLBCL (n=12), FL (n=3), FL3b (n=3) and trFL (n=4). Pt characteristics include: median age of 70 (38–81) years; median of 3 (1–10) prior lines of therapy; 7 (32%) pts had prior CAR-T therapy; 17 (77%) and 19 (86%) pts had disease refractory to last prior therapy and prior anti-CD20 therapy, respectively. Median follow-up duration was 9.6 (0.7–23.7) months. The most frequent treatment-related adverse events (AEs) were neutropenia (45.4%), fatigue, nausea and diarrhea (all 36.4%). Cytokine release syndrome (CRS) was observed in 2 pts (9.1%; both Gr 1 by ASTCT 2019 criteria). One dose-limiting toxicity (Gr 3 new onset atrial fibrillation) was observed in the 40mg cohort. The maximum tolerated dose was not exceeded. The most common Gr ≥3 and serious AEs were both neutropenia, observed in 8 (36.4%) and 3 (13.6%) pts, respectively. Two (9.3%) Gr 5 AEs occurred: sudden cardiac death (n=1) and respiratory failure (n=1); neither was deemed treatment related. No immune effector cell-associated neurotoxicity was observed. The Table shows preliminary efficacy data. Preliminary efficacy in the dose-escalation cohort. Conclusions: These data indicate that M-Pola has an acceptable safety profile, with no Gr ≥2 CRS observed, and promising efficacy in pts with R/R NHL with predominantly aggressive disease. The Phase II expansion cohort in R/R DLBCL is ongoing, with no mandatory hospitalization required. Clinical trial information: NCT03671018. [Table: see text]

Real-life experience with the combination of polatuzumab vedotin, rituximab, and bendamustine in aggressive B-cell lymphomas.

Transplant-ineligible relapsed/refractory (rr) diffuse large B-cell lymphoma (DLBCL) patients represent an unmet medical need. Polatuzumab vedotin (Pola), an anti-CD79b antibody-drug-conjugate (ADG), with bendamustine- rituximab(BR) has recently gained approval for these patients, both in the USA and Europe, based on the GO29365 phase IIb trial. Real-life data with Pola are extremely limited. We report the outcomes of 61 Greek patients, who received Pola-(B)R mainly within a compassionate use program. Treatment was given for up to six 21-day cycles. Bendamustine was omitted in three cases due to previous short-lived responses. Fourty-nine rrDLBCL(efficacy cohort-EC) and 58 rr aggressive B-NHL (safety cohort-SC) patients received at least 1 Pola-BR cycle. Twenty-one (43%) patients of the EC responded with 12/49 (25%) CR and 9/49 (18%) PR as best response. Median progression-free survival, overall survival and duration of response were 4.0, 8.5, and 8.5 months respectively, while 55% of patients experienced a grade ≥3 adverse event, mainly hematologic. Treatment discontinuations and death during treatment were mainly due to disease progression. Twenty-two (41%) patients received further treatment; 11/22 are still alive, including one after CAR-T cells, and two after stem cell transplantation. Our data confirm that Pola-BR is a promising treatment for rrDLBCL patients, inducing an adequate response rate with acceptable toxicity. Pola-BR could be used as bridging therapy before further consolidative treatments.

Polatuzumab Vedotin-Based Salvage Chemotherapy in the Third-Line or Above Treatment for Diffuse Large B-Cell Lymphoma

Introduction Diffuse large B-cell lymphoma (DLBCL) is the most common B-cell malignancy worldwide. A sizable fraction of these patients ended up succumbing to this fatal disease, so the standard of care after the second-line chemotherapy and/or autologous stem cell transplants (ASCT) remains to be improved. Polatuzumab vedotin-piiq (PoV), an anti-CD79b antibody-drug conjugate, gained accelerated approval by the U.S. Food and Drug Administration in June, 2019. The phase II randomized controlled study (GO29365) showed PoV in combination with bendamustine and rituximab (BR) conferred an additional 22% complete response rate for relapsed/refractory DLBCL, compared with BR alone (40% vs. 18%) . Interestingly, how PoV fares when combined with other salvage therapy remains as an open question. Method DLBCL patients who developed progressive diseases after at least 2 prior lines of therapy including R-CHOP and not previously treated with BR were enrolled into this study between Nov. 2018 and Apr. 2020 at the National Taiwan University Hospital. PoV was given at 1.8 mg/kg in combination with salvage chemotherapies based on clinicians' choices. The compassionate use of PoV was approved by the ethics committee, and clinical data were retrospectively analyzed. Results Thirty-two patients were enrolled in this study. According to the Hans' criteria of immunohistochemical subtypes, 13 patients were germinal center B cell-like (GCB), 17 were non-GCB, and 2 patients were unclassifiable. The median age was 62.5 years (range 20-82). At diagnosis, 26 (81%) patients had stage III or IV diseases, 22 (68.8%) had extranodal involvement, and 24 (75%) had the IPI scores equaled to 3 or higher. The median of failed prior lines of treatment was 4 (range 2-11), including 7 (21.9%) relapsing from ASCT and 16 (50%) were of primary refractory disease. Regarding combination therapies, 20 (62.5%) received BR, 5 (15.6%) had rituximab, 5 (15.6%) had rituximab/carmustine-containing regimens, and rituximab/gemcitabine-based ones were given to 4 (12.5%) patients. The median of cycles of PoV was 4 (range 1-7). Notably, the combinatory use of PoV and salvage chemotherapy helped transition 5 patients to ASCT and 4 to allogeneic SCT. The median overall survival (OS) was 8.9 months (95% confidence interval 6.2-not estimable) with the median follow-up of 11.4 months (range 0.3-20.7). The overall response rate (ORR) was 45.2%, including 29.1% complete response (CR) and 16.1% partial response (PR). The patients achieving CR or PR after PoV had better overall survival (OS) than those who did not (median OS: not reached (NR) vs. 5.6 months, p=0.0001, Figure A). The ORR for patients failing prior 2, 3, 4, and ≥5 lines of treatment were 50% (3/6), 40% (2/5), 50% (4/8), and 42% (5/12), respectively. The patients failing prior 4 lines of treatment had better OS than those with failed prior 5 or more lines (NR vs. 6.47 months). Non-GCB patients had better ORR (69.2% vs. 30.8%) and OS (NR vs. 6.23 months) than GCB ones did. Intriguingly, the patients received SCT had better OS compared with the others (NR vs. 6.23 months, p=0.011, Figure B). As for grade 3 &amp; 4 hematological adverse effects, 16 (50%) patients developed anemia, 20 (62.5%) had thrombocytopenia, and 18 (56.3%) were neutropenic. Grade 5 toxicities included pneumonia (2 patients, 6.3%), fungemia (1, 3.1%), intracranial hemorrhage (1, 3.1%), and other infections (2, 6.3%). Conclusion As the third-line or above treatment for DLBCL in this study, the efficacy and safety associated with PoV-based therapies not only were encouraging but also helped bridge to transplants. The application of this monoclonal antibody-drug conjugate in future clinical trials for DLBCL is expected. Figure Disclosures Tsai: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Chugai: Honoraria; Harvester: Honoraria; Janssen: Honoraria; Kirin: Honoraria; Takeda: Honoraria; BMS: Honoraria; Astellas: Honoraria; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ko:Roche: Honoraria. Cheng:Roche: Honoraria. Huang:MundiPharma: Honoraria; Chugai: Honoraria; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; Janssen: Honoraria; Takeda: Honoraria; Bristol Meyer &amp; Squibb: Honoraria.

Polatuzumab vedotin, an anti-CD79b antibody-drug conjugate for the treatment of relapsed/refractory diffuse large B-cell lymphoma.

Refractory/relapseddiffuse large B-cell lymphomaremains a major unmet medical need with poor outcome, especially for patients considered ineligible for stem cell transplant. Polatuzumab vedotin (PV) is a first-in-class anti-CD79b antibody-drug conjugatethat contains the microtubule inhibitor monomethyl auristatin E. The development of PV is currently very active. This drug was USFDA approved in 2019 in combination with bendamustine and rituximabfor the treatment of refractory/relapsed diffuse large B-cell lymphoma in third line and more, after demonstrating relevant efficacy and acceptable safety in a pivotal randomized Phase II trial. This review summarizes the features of this new drug with the primary focus on the clinical work supporting efficacy, relevance and tolerability of PV.

Polatuzumab vedotin: an investigational anti-CD79b antibody drug conjugate for the treatment of diffuse large B-cell lymphoma

ABSTRACT Introduction New agents for managing B-cell non-Hodgkin lymphomas (NHLs) are needed, particularly for high-risk and relapsed or refractory patients. Antibody–drug conjugates (ADCs) provide targeted drug delivery to tumors with a broaden therapeutic index of cytotoxic agent, reducing their systemic toxicity while increasing intracellular concentrations. Polatuzumab vedotin, an anti-CD79b conjugated to the microtubule inhibitor monomethyl auristatin E (MMAE) raises particular interest. Areas covered We discuss here polatuzumab vedotin development, challenges of designing a successful ADC, preclinical studies and recent trials, leading to FDA approval and the ongoing phase III POLARIX trial. Expert opinion Clinical data from early studies hold promises for polatuzumab vedotin in association with rituximab-bendamustine in relapsed or refractory (R/R) DLBCL and other combinations are investigated in this setting. In first line, with rituximab, cyclophosphamide, doxorubicin and prednisone (R-CHP), promising results lead to develop the phase III POLARIX trial that may represent a new advance for untreated patients. If dosing and scheduling are adequately managed to avoid peripheral neuropathy risk, polatuzumab vedotin might become a key component of DLBCL therapeutic management. This antibody drug conjugate also offers new opportunities of combination with non-cytotoxic agents or immunological interventions that might reshape the treatment of DLBCL in the future.

Polatuzumab Vedotin, an Antibody-Drug Conjugate Targeting CD79b, Is a Highly Active Agent Against Burkitt Lymphoma and Primary Mediastinal B-Cell Lymphoma

Introduction Mature B-cell lymphoma (MBL) accounts for approximately 60% of all non-Hodgkin lymphoma (NHL) in children and adolescents (Cairo et al, Blood, 2007). MBL in children and adolescents is comprised of approximately 75-80% Burkitt lymphoma (BL), 15-20% diffuse large B cell lymphoma (DLBCL) and 1-2% primary mediastinal B-cell lymphoma (PMBL). However, despite the differences in histology they are treated uniformly in children and adolescents (Cairo, BJH, 2016). The use of short and intense multiagent chemotherapy alone and in combination with rituximab (R) results in ≥90% event-free survival (EFS) in children and adolescents with BL and DLBCL (Cairo et al, JCO, 2012; Goldman/Cairo Leukemia, 2013; BJH, 2014). However, similar chemotherapy approaches in adolescents and young adults with PMBL have only resulted in a 60-70% EFS (Gerrard/Cairo et al, Blood, 2013). Furthermore, patients with induction failure, recurrent or refractory MBL have a dismal prognosis with ≤30% overall survival (OS) with current re-induction platforms and autologous stem cell transplantation (Cairo et al, BJH, 2018). Newer therapeutic strategies are urgently needed for recurrent/refractory patients with MBL, especially those with the BL subtype and newly diagnosed and refractory patients with PMBL (Cairo, BJH, 2019). We previously demonstrated that Obinutuzumab (O), a new type II anti-CD20 monoclonal antibody, is an active agent against both BL and PMBL (Awasthi/Cairo et al, BJH, 2015). Additionally, we have previously demonstrated high expression of CD79b in children and adolescents with BL and PMBL (Miles/Cairo et al, BJH 2007). Polatuzumab vedotin (PV), an anti-CD79b antibody-drug conjugate, recently approved by the FDA in adults with recurrent/refractory DLBCL has been demonstrated to be an active agent alone and in combination with chemotherapy in all molecular forms of adult DLBCL (Pfeifer et al, Leukemia, 2015; Corrinna et al, Lancet Oncology, 2015; Morschauser et al, Lancet Onc, 2019; Tilly et al, Lancet Onc, 2019). However, the efficacy of PV alone or in combination with R or O against other subtypes of B-NHL, including BL and PMBL, is relatively unknown. Objective To determine the in-vitro cytotoxicity and changes in in-vivo survival in a BL NSG xenograft model of PV alone or in combination with O vs R against R-sensitive and R-resistant BL and PMBL. Methods We compared the cytotoxicity of PV±R (10 ug/ml) vs PV±O (10 ug/ml) against R-sensitive BL (Raji) and R-resistant BL (Raji 4RH) and PBML (Karpas-1106p) alone or with ex-vivo expanded NK cells (Chu/Cairo et al, Can Imm Res, 2015) (10:1 E:T) by the DELFIA cytotoxicity assay. PV and O were generously supplied by Genentech and Roche, respectively. Furthermore, NSG mice (NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ) were xenografted with luciferase positive BL (Raji, Raji 4RH) and PMBL cells (Karpas-1106p) and treated with PV (5 mg/kg) + O (20 mg/kg) vs PV + R (20 mg/kg) vs PV vs IgG isotype control vs PV + O + NK vs PV + R + NK vs PV + NK vs O + NK vs R + NK vs PBS (without tumor) and tumor burden was compared between treatment groups using the IVIS bioluminescence system and probability of OS by KM method as we have previously described (Chu/Cairo et al, Can Imm Res, 2015). Results PV + O + NK induced significantly more in-vitro cytotoxicity against BL Raji compared to PV + R + NK (p&lt;0.007) vs PV, R or O + NK (p&lt;0.0001), BL (Raji 4RH [R-resistant BL]) PV + O vs PV + R (p&lt;0.004) and O, R or PV (p&lt;0.002) and against PMBL (Karpas-1106p) PV + O + NK vs PV + R + NK (p&lt;0.006) vs O, R, or PV + NK (p&lt;0.001) (Fig. 1A, 1B, 1C, respectively). Most importantly, PV + O + NK vs PV + R + NK vs PV + NK + IgG isotype control significantly enhanced probability of survival in BL (Raji) and BL (Raji 4RH) NSG xenografts (p&lt;0.03 and (p&lt;0.05), (95.5 vs 50.4 days) (185 vs 47 days), respectively (Fig. 2A and 2B, respectively). Conclusions PV alone and in combination with O significantly induces cytotoxicity against BL, R-resistant BL and PMBL. Most importantly, PV + O + NK cells result in a significantly improved OS in BL and R-resistant BL NSG xenografts. These preclinical results suggest that PV should be considered for investigation in patients with both recurrent/refractory BL and PMBL and in patients with newly diagnosed disease with either high risk features or those with poor responses to induction therapy. Authors AA, MB &amp; AA are all considered co-primary first authors Disclosures Klein: Roche: Employment, Equity Ownership, Patents &amp; Royalties. Cairo:Jazz Pharmaceuticals: Other: Advisory Board, Research Funding, Speakers Bureau; Osuka: Research Funding; Miltenyi: Other: MTA.

Abstract 3628: T cell-dependent bispecific antibody anti-CD79b/CD3 as a potential therapy for B-cell malignancies

Abstract T-cell recruiting bispecific antibodies and antibody fragments have been used to harness the cytotoxic potential of T cells for cancer treatment. We have adopted a knobs-into-holes antibody format and produced T-cell dependent bispecific antibodies (TDB), as full length, humanized IgG1 antibodies with natural antibody architecture, which allow one arm to target various B cell antigens while the other arm recruits T cells by binding to the CD3ϵ subunit of the T-cell receptor. One B cell antigen targeted is CD79b, a component of the B cell receptor complex, which has been clinically validated by an anti-CD79b antibody-drug conjugate (ADC) as a safe and effective therapeutic target for B cell malignancies (Leukemia 2015 Pfeifer et.al). In the present work, we show that anti-CD79b/CD3 TDB is active against lymphoma cells with a wide range of CD79b antigen levels in vitro. In addition, anti-CD79b/CD3 TDB appears to be insensitive to the status of cellular signaling pathways in lymphoma cells as it is active against cell lines that are resistant to the BTK inhibitor ibrutinib or an anti-CD79b ADC with a cleavable tubulin inhibitor as the payload. In vivo, anti-CD79b/CD3 TDB administration inhibited tumor growth in B-cell lymphoma xenograft models and resulted in potent B-cell depletion in the blood and spleens in a humanized murine model. To assess the safety of targeting CD79b with a T-cell recruiting bispecific antibody in non-human primates, a surrogate anti-cynoCD79b/CD3 TDB with comparable in vitro potency was produced with a target arm that recognizes cynomolgus monkey CD79b and the same anti-CD3 arm. In a single dose pharmacokinetic/pharmacodynamics/safety study, anti-cynoCD79b/CD3 TDB administration at 1mg/kg resulted in potent B cell depletion, as well as T cell activation and proliferation, which was assessed by flow cytometry on blood and lymphoid tissue and immunohistochemistry on lymphoid tissue. The pharmacokinetic properties of anti-cynoCD79b/CD3 TDB resembled that of IgG antibodies; though with a faster clearance likely due to CD79b antigen internalization and enhanced binding to CD3 when compared to previously described anti-CD20/CD3 TDB. Transient cytokine release was observed as elevated levels of IL-2, IL-6, IFN-gamma and TNF-alpha were detected within 24 hours following administration. Anti-cynoCD79b/CD3 TDB was well-tolerated in the majority of dosed animals without toxicologically significant findings. Collectively, these preclinical data suggest anti-CD79b/CD3 TDB can be a potential therapeutic agent in B cell malignancies. Citation Format: Peiyin Wang, Maria Hristopoulos, Robyn Clark, Yvonne Chen, Diego Ellerman, Mary Mathieu, Christoph Spiess, Jessica Li, Cecile Chalouni, Siddharth Sukumaran, Eric Stefanich, Jeffrey Wallin, Robert Li, Tanja Zabka, Klara Totpal, Mark Dennis, Allen Ebens, Stephen Gould, Andrew Polson, Liping Laura Sun. T cell-dependent bispecific antibody anti-CD79b/CD3 as a potential therapy for B-cell malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3628. doi:10.1158/1538-7445.AM2017-3628

An Anti-CD79B Antibody–Drug Conjugate Is Active in Non-Hodgkin Lymphoma

Abstract Polatuzumab vedotin is safe and shows activity in relapsed or refractory B-cell non-Hodgkin lymphoma.

Two doses of polatuzumab vedotin (PoV, anti-CD79b antibody-drug conjugate) in patients (pts) with relapsed/refractory (RR) follicular lymphoma (FL): Durable responses at lower dose level.

8503 Background: Based on early evidence of cumulative toxicity of PoV at a dose of 2.4 mg/kg (Morschhauser ASH 2014 NCT01691898), a dose of 1.8 mg/kg was explored. We report updated results of the...

Safety and activity of the anti-CD79B antibody–drug conjugate polatuzumab vedotin in relapsed or refractory B-cell non-Hodgkin lymphoma and chronic lymphocytic leukaemia: a phase 1 study

Patients with relapsed or refractory B-cell non-Hodgkin lymphoma (NHL) have an unfavourable prognosis with few treatment options. Polatuzumab vedotin is an antibody-drug conjugate containing an anti-CD79B monoclonal antibody conjugated to the microtubule-disrupting agent monomethyl auristatin E. We aimed to assess the safety and clinical activity of polatuzumab vedotin in relapsed or refractory B-cell NHL and chronic lymphocytic leukaemia (CLL). In this phase 1, multicentre, open-label study, we enrolled patients with documented NHL or CLL expected to express CD79B (confirmation of CD79B expression was not required) and for whom no suitable therapy of curative intent or higher priority existed from 13 centres. The primary endpoints of the study were to assess safety and tolerability, determine the maximum tolerated dose, and identify the recommended phase 2 dose of polatuzumab vedotin as a single agent and in combination with rituximab. A 3 + 3 dose-escalation design was used in which we treated patients with polatuzumab vedotin (0·1-2·4 mg/kg every 21 days) in separate dose-escalation cohorts for NHL and CLL. After determination of the recommended phase 2 dose, we enrolled patients with relapsed or refractory diffuse large B-cell lymphoma and relapsed or refractory indolent NHL into indication-specific cohorts. We also enrolled patients with relapsed or refractory NHL into an additional cohort to assess the feasibility of the combination of polatuzumab vedotin and rituximab 375 mg/m(2). Patients who received any dose of polatuzumab vedotin were available for safety analyses. This study is registered with ClinicalTrials.gov, number NCT01290549. Between March 21, 2011, and Nov 30, 2012, we enrolled 95 patients (34 to the NHL dose-escalation cohort, 18 to the CLL dose-escalation cohort, 34 with NHL to the expansion cohort at the recommended phase 2 dose, and nine with NHL to the rituximab combination cohort; no expansion cohort of CLL was started due to lack of activity in the dose-escalation cohort). The recommended phase 2 dose in NHL was 2·4 mg/kg as a single agent and in combination with rituximab; the maximum tolerated dose in CLL was 1·0 mg/kg as a result of dose-limiting toxic effects reported in two of five patients given 1·8 mg/kg. Grade 3-4 adverse events were reported in 26 (58%) of 45 patients with NHL treated at the single-agent recommended phase 2 dose, and the most common grade 3-4 adverse events were neutropenia (18 [40%] of 45), anaemia (five [11%]), and peripheral sensory neuropathy (four [9%]). Serious adverse events were reported in 17 (38%) of 45 patients, and included diarrhoea (two patients), lung infection (two patients), disease progression (two patients), and lung disorder (two patients). Seven (77%) of nine patients in the rituximab combination cohort had a grade 3-4 adverse event, with neutropenia (five [56%]), anaemia (two [22%]), and febrile neutropenia (two [22%]) reported in more than one patient. 11 (12%) of 95 patients died during the study: eight with relapsed or refractory diffuse large B-cell lymphoma (due to progressive disease in four patients, infections in three patients [two treatment related], and treatment-related worsening ascites in one patient) and three with relapsed or refractory CLL (due to progressive disease, pulmonary infection, and pneumonia; none thought to be treatment-related). At the recommended phase 2 dose, objective responses were noted in 23 of 42 activity-evaluable patients with NHL given single-agent polatuzumab vedotin (14 of 25 with diffuse large B-cell lymphoma, seven of 15 with indolent NHL, and two with mantle-cell lymphoma) and seven of nine patients treated with polatuzumab vedotin combined with rituximab. No objective responses were observed in patients with CLL. Polatuzumab vedotin has an acceptable safety and tolerability profile in patients with NHL but not in those with CLL. Its clinical activity should be further assessed in NHL. Genentech.

Pre-Clinical Characterization of T Cell-Dependent Bispecific Antibody Anti-CD79b/CD3 As a Potential Therapy for B Cell Malignancies

T-cell recruiting bispecific antibodies and antibody fragments have been used to harness the cytotoxic potential of T cells for cancer treatment. As an example, encouraging clinical responses have been reported with the B cell targeting Blinatumomab, a 55-kDa fusion protein composed of two single-chain antibody fragments (scFvs). However, the therapeutic promise of many reported bispecific antibodies and fragments is often limited by unfavorable pharmacokinetics and administration schedule, immunogenicity, and a propensity towards aggregation. We have adopted a knobs-into-holes (KIH) antibody format and produced T-cell dependent bispecific antibodies (TDB), which allow one arm to target various B cell antigens while the other arm recruits T cells by binding to the CD3e subunit of the T-cell receptor. These B cell targeting TDBs are full length, humanized IgG1 antibodies with natural antibody architecture. Single dose pharmacokinetic/pharmacodynamic studies in cynomolgus monkeys show the KIH format TDBs are well tolerated in life, result in potent B cell depletion in peripheral and lymphoid tissue, and demonstrate pharmacokinetic properties resembling conventional antibody therapy.One B cell antigen targeted is CD79b, a component of the B cell receptor complex. CD79b is restricted to B cells, is highly prevalent on B cell leukemia and lymphomas, and has been clinically validated by an anti-CD79b antibody-drug conjugate as a safe and effective therapeutic target for B cell malignancies (ASCO 2014 abstract#8519). In our present work, we show that anti-CD79b/CD3 TDB can be produced and purified from E.coli, free of homodimer and aggregates. Anti-CD79b/CD3 TDB is a conditional agonist, activating CD3+T cells only in the presence of CD79b expressing B cells. In vitro, it induces potent B cell killing in a T-cell dependent manner, and is broadly active against lymphoma cell lines with a wide range of CD79b antigen levels. Compared to bispecific antibodies targeting some other B cell antigens, anti-CD79b/CD3 TDB appears to be more potent in autologous B cell killing assays with human PBMCs isolated from healthy donors. Taking advantage of antibodies with a range of binding affinities, we show that the B cell cytotoxic potency of anti-CD79b/CD3 TDB can be enhanced with increased binding affinity of either the anti-CD79b arm or the anti-CD3 arm in vitro. To assess the therapeutic potential of anti-CD79b/CD3 TDB, we further demonstrate that it is active in killing B lymphoma cells isolated from leukemia and lymphoma patients. Collectively, these preclinical data suggest anti-CD79b/CD3 TDB may be a promising agent for clinical development in B cell malignancies. DisclosuresSun:Genentech: Employment. Chen:Genentech: Employment. Chen:Genentech: Employment. Dennis:Genentech: Employment. Ellerman:Genentech: Employment. Johnson:Genentech: Employment. Mathieu:Genentech: Employment. Oldendorp:Genentech: Employment. Polson:Genentech: Employment. Reyes:Genentech: Employment. Stefanich:Genentech: Employment. Wang:Genentech: Employment. Wang:Genentech: Employment. Zheng:Genentech: Employment. Ebens:Genentech: Employment.

Final Results Of a Phase I Study Of The Anti-CD79b Antibody-Drug Conjugate DCDS4501A In Relapsed Or Refractory (R/R) B-Cell Non-Hodgkin Lymphoma (NHL)

BackgroundDCDS4501A (DCDS), an anti-CD79b monoclonal antibody (Ab), is conjugated to the anti-mitotic agent MMAE. We previously determined a recommended Phase II dose (RP2D) of 2.4 mg/kg every 21 days (q21d), and clinical activity in R/R B-cell NHL at doses ≥ 1.8 mg/kg (Palanca-Wessels et al. ASH 2012). Here we update results from patients (pts) treated at 1.8 mg/kg and from the 2.4 mg/kg expansion cohort. MethodsWe evaluated ongoing safety, tolerability, pharmacokinetics (PK) and activity of DCDS with or without rituximab (RTX) at 375 mg/m2 q21d in pts with R/R DLBCL and indolent (i)NHL. ResultsSixty pts were treated with DCDS (6 at 1.8 mg/kg, 45 at 2.4 mg/kg) and DCDS+RTX (9, DCDS at 2.4 mg/kg). Median age 68 yrs (range 20-86); 82% ECOG PS<2; median 4 prior regimens (range 1-14); 97% had prior RTX; 28% had prior autologous stem cell transplant. The DCDS+RTX safety profile did not differ from DCDS monotherapy. Patients received a median of 7 cycles (range 1-20) of DCDS and 10 cycles (range 1-17) of DCDS + RTX; 18 patients continue to receive study treatment. Treatment-emergent adverse events (TEAEs) included neutropenia (50%), diarrhea (45%), nausea (40%), pyrexia (38%), peripheral neuropathy (25%), peripheral sensory neuropathy (20%), and hypokalemia (20%). Grade ≥ 3 AEs in ≥5% of pts included neutropenia (43%), anemia (13%), thrombocytopenia (7%), hyperglycemia (7%), fatigue (5%) and diarrhea (5%). Grade ≥ 3 infection was reported in 8 (13%) pts. Twenty-two (37%) pts reported a serious AE. TEAEs related to peripheral neuropathy (PN) were reported in 32 (53%) pts with median time to first onset of 63 days. 22/32 pts (69%) had worsening PN with median time to worsening of 49 days. Grade ≥ 3 peripheral neuropathy/peripheral sensory neuropathy/peripheral motor neuropathy was reported in 5 (8%) patients. PN was managed with dose delays and dose reductions resulting in complete reversal in 7 (22%) pts. Treatment discontinuations for AEs were reported in 25 (42%) pts including 17 for PN. Seven pts (12%) had ≥ 1 dose reduction including 3 for PN and 2 for neutropenia. Twenty-six patients (43%) had ≥ 1 dose delay including 14 for neutropenia and 6 for PN. Six deaths were reported within 60 days of last study treatment assessed as unrelated to DCDS. Exposure of Ab-conjugated (ac) MMAE, total Ab, and unconjugated MMAE increased with dose. Maximal concentrations of unconjugated MMAE were >100-fold lower than acMMAE with an average Cycle 1 value of 5-9 ng/mL at the 2.4 mg/kg ADC dose level. Moderate accumulation of acMMAE and total Ab on the q21d dosing schedule was observed with no accumulation of free MMAE. Overall objective responses were observed in 27/51 (53%) DCDS and 7/9 (78%) DCDS+RTX pts. Objective (OR) and complete responses (CR) by histology were as follows:The median PFS for DLBCL patients treated with DCDS or DCDS + RTX was 149 days. The median PFS for iNHL patients treated with DCDS or DCDS + RTX was 241 days. ConclusionsDCDS and DCDS+RTX were generally well-tolerated. Neutropenia and PN were the principal toxicities. PN was reversible in some patients with dose delays and reductions. Encouraging anti-tumor activity was observed in heavily pretreated pts with R/R NHL. Updated results from this Phase I study will be presented. An ongoing randomized Phase II study of DCDS+RTX versus a CD22-directed ADC (DCDT2980S) with the same linker-cytotoxic agent in patients with R/R DLBCL and follicular lymphoma will further assess the efficacy of DCDS in the treatment of NHL. Additional studies of DCDS combined with immunochemotherapy are being planned. Disclosures:Palanca-Wessels:Genentech, inc.: Research Funding. Off Label Use: anti-CD79b Antibody-Drug Conjugate in r/r B-cell NHL. Salles:Genentech, inc.: Consultancy. Czuczman:Genentech, inc.: Consultancy, Honoraria. Flinn:Genentech, inc.: Research Funding. Sehn:Genentech, inc.: Consultancy, Honoraria, Research Funding. Tilly:Genentech, inc.: Honoraria. Advani:Genentech, inc.: Research Funding. Casasnovas:Genentech, inc.: Research Funding. Press:Genentech, inc.: Consultancy, Research Funding. Yalamanchili:Genentech, inc.: Employment. Kahn:Genentech, inc.: Employment. Lu:Genentech, inc.: Employment. Chai:Genentech, inc.: Employment. Chu:Genentech, inc.: Employment. Morschhauser:Genentech, inc.: Honoraria, Research Funding.DCDSDCDS + RTXORCRORCRR/R DLBCL15/31 (48%)3/31 (10%)1/10R/R iNHL7/15 (47%)3/15 (20%)5/5 (100%)2/5 (40%)