anti-CD20 mAb Therapy Research Articles

A Review of Anti-CD20 Antibodies in the Management of B-Cell Lymphomas

Anti-CD20 monoclonal antibodies (mAbs) have revolutionized the treatment of lymphomas by improving the survival of patients, particularly in conjunction with chemotherapy. Until recently, the gold standard was based on the utilization of Rituximab (RTX) combined with chemotherapy. With our better understanding of monoclonal antibody (mAb) engineering, anti-CD20 mAb therapy has evolved to enhance clinical outcomes by improving pharmacokinetics, safety, activity and immunogenicity. Efforts to improve the on-targeting CD20 expressed on lymphomas through novel bioengineering techniques have led to the development of newer anti-CD20 mAbs that have accentuated complement-dependent cytotoxicity (CDC), antibody-dependent cell medicated cytotoxicity (ADCC), and/or a direct killing effect. There are several anti-CD20 monoclonal antibodies that have been evaluated for the treatment of lymphomas, some of which are now approved in addition to RTX.

Anti-CD20 monoclonal antibody therapy in postpartum women with neurological conditions.

Postpartum, patients with multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) have increased risk for disease activity. Anti-CD20 IgG1 monoclonal antibodies (mAb) are increasingly used as disease-modifying therapies (DMTs). Patients may wish to both breastfeed and resume DMT postpartum. This study aimed to determine the transfer of anti-CD20 IgG1 mAbs, ocrelizumab, and rituximab (OCR/RTX), into mature breastmilk and describe maternal and infant outcomes. Fifty-seven cis-women receiving OCR/RTX after 59 pregnancies and their infants were enrolled and followed up to 12M postpartum or 90 days post-infusion. Breastmilk was collected pre-infusion and serially up to 90 days and assayed for mAb concentration. Medical records and patients' questionnaire responses were obtained to assess neurologic, breastfeeding, and infant development outcomes. The median average concentration of mAb in breastmilk was low (OCR: 0.08 μg/mL, range 0.05-0.4; RTX: 0.03 μg/mL, range 0.005-0.3). Concentration peaked 1-7 days post-infusion in most (77%) and was nearly undetectable after 90 days. Median average relative infant dose was <1% (OCR: 0.1%, range 0.07-0.7; RTX: 0.04%, range 0.005-0.3). Forty-three participants continued to breastfeed post-infusion. At 8-12 months, the proportion of infants' growth between the 3rd and 97th World Health Organization percentiles did not differ for breastfed (36/40) and non-breastfed (14/16, p > 0.05) infants; neither did the proportion with normal development (breastfed: 37/41, non-breastfed: 11/13; p > 0.05). After postpartum infusion, two mothers experienced a clinical relapse. These confirm minimal transfer of mAb into breastmilk. Anti-CD20 mAb therapy stabilizes MS activity before conception to the postpartum period, and postpartum treatments appears to be safe and well-tolerated for both mother and infant.

Pharmacogenomic Analyses Implicate B Cell Developmental Status and MKL1 as Determinants of Sensitivity toward Anti-CD20 Monoclonal Antibody Therapy.

Monoclonal antibody (mAb) therapy directed against CD20 is an important tool in the treatment of B cell disorders. However, variable patient response and acquired resistance remain important clinical challenges. To identify genetic factors that may influence sensitivity to treatment, the cytotoxic activity of three CD20 mAbs: rituximab; ofatumumab; and obinutuzumab, were screened in high-throughput assays using 680 ethnically diverse lymphoblastoid cell lines (LCLs) followed by a pharmacogenomic assessment. GWAS analysis identified several novel gene candidates. The most significant SNP, rs58600101, in the gene MKL1 displayed ethnic stratification, with the variant being significantly more prevalent in the African cohort and resulting in reduced transcript levels as measured by qPCR. Functional validation of MKL1 by shRNA-mediated knockdown of MKL1 resulted in a more resistant phenotype. Gene expression analysis identified the developmentally associated TGFB1I1 as the most significant gene associated with sensitivity. qPCR among a panel of sensitive and resistant LCLs revealed immunoglobulin class-switching as well as differences in the expression of B cell activation markers. Flow cytometry showed heterogeneity within some cell lines relative to surface Ig isotype with a shift to more IgG+ cells among the resistant lines. Pretreatment with prednisolone could partly reverse the resistant phenotype. Results suggest that the efficacy of anti-CD20 mAb therapy may be influenced by B cell developmental status as well as polymorphism in the MKL1 gene. A clinical benefit may be achieved by pretreatment with corticosteroids such as prednisolone followed by mAb therapy.

Rapid Tumor Debulking of Relapsed/Refractory CLL Patients By PI3Kδ Inhibition and Anti-CD20 Monoclonal Antibody Treatment

Introduction Effective multi-targeted drug combinations could rapidly achieve deep remissions in CLL allowing for defined duration treatment. The combination of a novel highly-specific phosphoinositide 3-kinase delta (PI3Kδ) inhibitor and casein kinase 1 epsilon (CSK1ε) inhibitor, umbralisib (UMB), and a glycoengineered chimeric monoclonal antibody (mAb) targeting a unique epitope on CD20, ublituximab (UBL), with the BCL2 inhibitor venetoclax (VEN) may decrease drug resistance, reduce risk of tumor lysis syndrome (TLS) and achieve higher levels of undetectable minimal residual disease (MRD). This triple agent therapy is being evaluated in relapsed or refractory CLL patients (U2-VEN, ClinicalTrials.gov NCT03379051). Patients received oral 800 mg UMB once-daily. For Cycle 1, UBL was given via IV on Day 1 (150 mg), Day 2 (750 mg), Day 8 (900 mg), Day 15 (900 mg), and then on Day 1 in Cycles 2 and 3 (900 mg); for 3 cycles of 28 days, followed by consolidation with UMB and VEN for cycles 4 to 24. Patient (n = 25) blood samples were collected Pre- and Post-treatment on days of UBL administration during cycles 1-3. Our studies focused on UMB and UBL treatment effects on: 1) The decrease in the circulating CLL tumor burden and thus the subsequent risk of TLS from the addition of VEN to the regimen; and 2) CD20 antigen loss on CLL cells, a major mechanism of anti-CD20 mAb resistance. Methods Blood was analyzed by clinical laboratory automated cell counter and then stained with antibodies against CD3, CD5, CD19, and CD20 for flow cytometry analysis. CLL cell counts were calculated from flow cytometry and clinical laboratory results. To quantitate CD20 surface molecules, peripheral blood mononuclear cells were isolated and stained for flow cytometry analysis with the addition of a Molecules of Equivalent Soluble Fluorochrome standard curve. All human specimen collection and usage was conducted with written informed consent after approval of our Institutional Research Subjects Review Board according to the ethical guidelines of the Declaration of Helsinki. Results Average CLL cell counts (47 x 109/L) decreased rapidly after administration of the first dose of UMB and UBL (C1D1 Post, 26 x 109/L), which rebounded the next day (C1D2 Pre, 43 x 109/L) and then decreased after the second treatment (C1D2 Post, 24 x 109/L). By Day 15, the average CLL cell count had dropped to 9 x 109/L, which decreased further to 5 x 109/L by the start of cycle 3 (Fig. 1). Notably, the variation in CLL cell counts (error bars) decreases over treatment time, suggesting that most CLL patients' tumor burdens are decreasing to a similar low level independent of starting CLL cell count. The change in average CLL cell count between Pre and Post measurements is initially very high (45% decrease C1D1) with decreasing effectiveness over treatment time (8% decrease C3D1). This change could be due to the loss of CLL cell membrane CD20 levels leading to mAb resistance. Pre-treatment (C1D1 Pre) average CLL cell membrane CD20 levels (n=18) were 29,000 CD20 molecules/cell. This decreased to 9,000 molecules/cell after the first treatment (C1D1 Post), stabilized at 9,100 molecules/cell on the next day (C1D2 Pre) and then decreased further after the second treatment (C1D2 Post) to 1600 molecules/cell. After day 8 treatment, CD20 levels remained at 1,000 molecules/cell or less until the end of this study (C3D1). Discussion UMB and UBL rapidly decrease circulating CLL counts over three cycles of treatment, reducing most CLL patient tumor burden to similar low levels. This clinical response could facilitate addition of VEN in the 4thcycle of therapy by decreasing the risk of TLS. The rapid loss of surface CD20 from CLL cells to 1,000 CD20 molecules/cell or less by C1D8 Post has the potential to cause acquired resistance to anti-CD20 mAb therapy. This rapid and sustained loss of CD20 levels is consistent with that reported at standard doses for other anti-CD20 mAbs. However, an effect of concomitant UMB on CD20 levels cannot be ruled out. Previous work suggests that lower anti-CD20 mAb doses can prevent these large decreases in CD20 levels and increase UBL efficacy. In conclusion, our initial data show that treatment with a selective PI3Kδ and CSK1ε inhibitor (UMB) combined with an anti-CD20 mAb (UBL) is effective in decreasing CLL cell counts in all patients assessed in the U2-VEN clinical trial. However, treatment efficacy could be limited by large decreases in the CLL surface CD20 levels. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Pneumococcal Vaccination Practices in Patients With Multiple Sclerosis Receiving Anti-CD20 Monoclonal Antibodies After Pharmacy and Nursing Collaboration.

It is recommended that patients taking immunosuppressive anti-CD20 monoclonal antibodies (mAbs) receive pneumococcal vaccinations before their first dose to ensure optimal immune response. An initial medication use evaluation reviewed adherence to Centers for Disease Control and Prevention (CDC) pneumococcal immunization recommendations at the study site, and room for improvement was identified. The nursing team implemented workflow changes to increase nursing involvement in vaccination coordination, education, tracking, and administration. We sought to evaluate the impact of a nursing intervention on optimal pneumococcal vaccination administration rates in patients receiving anti-CD20 mAbs at a multiple sclerosis (MS) center. We performed a single-center, retrospective, pre/post medication use evaluation. Inclusion criteria were older than 18 years with a diagnosis of MS and received their first anti-CD20 mAb infusion at the study site during the preintervention or postintervention time frame. We included 406 and 73 patients in the preintervention and postintervention studies, respectively. The nursing intervention significantly improved the percentage of patients receiving optimal pneumococcal vaccination before their first infusion from 58% to 84% and significantly reduced the number with unknown vaccination status from 17% to 3%. Patients who received optimal follow-up vaccination with 23-valent pneumococcal polysaccharide vaccine after optimal 13-valent pneumococcal conjugate vaccine administration improved from 9% to 56%. A nursing team intervention improved adherence to CDC pneumococcal immunization recommendations for patients receiving anti-CD20 mAb therapy. This project highlights the value of interdisciplinary team collaboration between health system specialty pharmacies and specialized nursing teams in the care of patients with MS.

P1103: INMIND: A PHASE 3 STUDY OF TAFASITAMAB PLUS LENALIDOMIDE AND RITUXIMAB VERSUS PLACEBO PLUS LENALIDOMIDE AND RITUXIMAB FOR RELAPSED/REFRACTORY FOLLICULAR LYMPHOMA (FL) OR MARGINAL ZONE LYMPHOMA (MZL)

Background: Patients (pts) with indolent non-Hodgkin lymphoma (NHL) subtypes FL or MZL respond to first-line treatment but relapse is common; there is no standard treatment for pts with relapsed/refractory (R/R) FL or MZL. Tafasitamab (TAFA) is an Fc-engineered humanized monoclonal antibody (mAb) against CD19, which is broadly expressed in FL and MZL and regulates proliferation via B-cell receptor signaling. In preclinical studies, TAFA has shown activity against NHL cell lines in combination with rituximab (anti-CD20 mAb) and lenalidomide (LEN). TAFA monotherapy demonstrated promising clinical activity in a phase 2a study in pts with R/R NHL (NCT01685008), with an ORR of 29% (n/N=10/34) in pts with FL and 33% (n/N=3/9) in pts with MZL. In an ongoing phase 2, single-arm study (L-MIND, NCT02399085), TAFA + LEN followed by TAFA alone demonstrated an ORR of 57.5% (n/N=46/80) with CR of 40% (n/N=32/80) and median DOR of 34.6 mo (95% CI: 26.1–NR), in pts with R/R diffuse large B-cell lymphoma (FDA approved indication). These observations suggest a potential clinical benefit of TAFA + LEN and rituximab for pts with R/R FL or MZL. Aims: Phase 3 double-blind, placebo-controlled, randomized study designed to investigate whether TAFA + LEN and rituximab provides improved clinical benefit compared with LEN and rituximab in pts with R/R FL or MZL. Methods: Pts will be randomized 1:1 to receive TAFA (12 mg/kg IV on days 1, 8, 15, and 22 of 28-day cycle [cycles 1–3], then days 1 and 15 [cycles 4–12]) + LEN (20 mg PO QD [or starting dose 10 mg PO QD if creatinine clearance ≥30 to <60 mL/min], days 1–21/cycle for 12 cycles) and rituximab (375 mg/m2 IV on days 1, 8, 15, and 22 of cycle 1, then day 1 of cycles 2–5), or placebo (0.9% saline solution IV) + LEN and rituximab. Stratification will include progression of disease within 24 mo (FL; yes vs no), refractoriness to prior anti-CD20 mAb therapy (FL; yes vs no), and number of prior lines of therapy (FL or MZL; <2 vs ≥2). Radiological (PET) assessment will be performed at baseline, every 12 (± 2) weeks in year 1, 16 (± 2) weeks in years 2–3, and 24 (± 3) weeks in years 4–6; additional assessment performed within 4 (± 2) weeks if progressive disease confirmed before end-of-treatment (EOT) visit. The primary study endpoint is PFS (investigator assessed [INV] by Lugano 2014 criteria) for pts with FL. Key secondary endpoints are PFS (INV) in the overall population (FL and MZL), PET-CR rate (INV) at EOT (90 days after last treatment) and OS in pts with FL. Other secondary endpoints include PET-CR rate (INV) at EOT and OS in the overall population, and ORR (INV), DOR (INV), health related quality of life, safety, and minimum residual disease-negativity rate at EOT in FL and the overall population. Inclusion criteria include age ≥18 y, histologically confirmed FL (grade 1, 2, or 3a) or MZL (nodal, splenic, or extranodal), documented R/R disease, ≥1 prior systemic anti-CD20 therapy (including anti-CD20 refractory disease), ECOG PS ≤2, adequate systemic organ function, and high tumor burden (per GELF criteria). Exclusion criteria include prior rituximab + LEN treatment, history of radiotherapy for other diseases (≥25% of bone marrow), nonhematologic malignancy, congestive heart failure (LVEF <50%), active systemic infection, known CNS lymphoma, or severe immunocompromised state. inMIND (NCT04680052, EudraCT2020-004407-13) is currently enrolling pts; planned enrollment is 528 pts with R/R FL and 60–90 pts with R/R MZL across North America, Europe, and Asia Pacific. Results: Not applicable. Summary/Conclusion: Not applicable.

Serologic response to mRNA COVID‐19 vaccination in lymphoma patients

Serologic response to <scp>mRNA COVID</scp>‐19 vaccination in lymphoma patients

Impaired Sars-Cov-2 Specific Antibody Responses in Patients Treated with Anti-CD20 Antibodies

It has been proposed that patients with hematologic malignancy and autoimmune diseases receiving anti-CD20 monoclonal antibody (mAb) therapy are particularly at risk of severe Coronavirus disease (COVID-19) because the profound and long-lasting B-cell depletion induced by anti-CD20 mAb may impair virus clearance and may also contribute to reactivation of latent viruses, especially hepatitis B and JC viruses.As of July 20, 2020, the total number of COVID-19 cases reported by the Italian authorities reached 245,000. The north of the country was mostly hit, and Milan and Brescia were among the Italian provinces that registered the highest number of COVID-19 cases. Consistent with this, a high number of COVID-19 patients affected with multiple types of hematological disorders (n. 137) and with multiple sclerosis (MS, n. 114) were referred to ASST Spedali Civili di Brescia. Antibodies to SARS-CoV-2 were analyzed in 70 patients with hematological disease, and in few patients with MS. Among these, 10 patients (7 with hematologic disease and 3 with MS) had received treatment with rituximab or ocrelizumab, two anti-CD20 mAbs, within 3 months prior to COVID-19 onset. Clinical indication to CD20-depleting treatment for patients with hematological disorders included Diffuse Large B Cell Lymphoma (DLBCL) or Follicular Non Hodgkin Lymphoma (NHL).Anti-spike protein (anti-S) and anti-nucleocapsid (anti-N) antibodies to SARS-CoV-2 were analyzed during the acute phase of infection and up to 3 months since the onset of symptoms by quantitative measurements of plasma or serum antibodies with luciferase immune precipitation assay systems (LIPS). With this technique, production of anti-S and anti-N antibodies has been demonstrated between day 8 and day 14 after onset of symptoms in immunocompetent individuals, whereas specific antibody production was delayed by few days in immunocompromised patients (Burbelo PD et al, medRxiv. 2020 Apr 24:2020.04.20.20071423).All 10 patients remained seronegative to SARS-CoV-2 for the first 20 days since onset of symptoms. One patient with DLBCL secondary to Follicular NHL had detectable anti-S and anti-N antibodies at day +25, and one patient with MS developed anti-N antibodies by day +23. Two patients, one with DLBCL secondary to Follicular NHL and one with Follicular NHL were still seronegative for both anti-S and anti-N antibodies at 133 and 74 days since onset of symptoms. Two MS patients were seronegative at the last examination, and one other MS patient was anti-S seronegative at day +74.Three of the 10 patients have died; all three were SARS-CoV-2 RT-qPCR+ and seronegative at the time of death.While it has been reported that SARS-CoV-2 is cleared without significant problems by the majority of people with MS or other autoimmune diseases on immunotherapy, these data indicate that treatment with anti-CD20 mAb may significantly alter humoral responses to the virus. Until a vaccine to SARS-CoV-2 is available, the risk-benefit ratio of anti-CD20 mAb therapy in areas with high rates of SARS-CoV-2 infection should be carefully weighed. Moreover, for patients with B-cell malignancies or autoimmune diseases, transient discontinuation of this therapy, or use of alternative therapeutic approaches, should be considered once an efficacious vaccine becomes available.This study was performed according to protocol NP-4000 (Comitato Etico Provinciale), and supported by Regione Lombardia and by the Division of Intramural Research, NIAID.Figure 1DisclosuresImberti:Biogen: Honoraria; Genzyme-Sanofi: Honoraria; Meck-Serono: Honoraria; Novartis: Honoraria; Biogen: Other: Advisory board; FISM (Fondazione Italiana Sclerosi Multipla): Research Funding; Regione Lombardia: Research Funding. Capra:Biogen: Other: travel grants, Speakers Bureau; Roche: Other: travel grants, Speakers Bureau; Celgene: Other: travel grants, Speakers Bureau; Merck: Other: travel grants, Speakers Bureau; Novartis: Other: travel grants, Speakers Bureau. Rossi:Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria; Abbvie: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Alexion: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Advisory board; Daiichi Sankyo: Consultancy, Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Notarangelo:NIAID, NIH: Research Funding. Cohen:NIAID, NIH: Research Funding.

Subcutaneous Epcoritamab Induces Complete Responses with an Encouraging Safety Profile across Relapsed/Refractory B-Cell Non-Hodgkin Lymphoma Subtypes, Including Patients with Prior CAR-T Therapy: Updated Dose Escalation Data

Subcutaneous Epcoritamab Induces Complete Responses with an Encouraging Safety Profile across Relapsed/Refractory B-Cell Non-Hodgkin Lymphoma Subtypes, Including Patients with Prior CAR-T Therapy: Updated Dose Escalation Data

Abstract 909: The role of checkpoints in Rituximab-mediated NK cell activation

Abstract Purpose: Despite the remarkable clinical success of anti-CD20 monoclonal antibody (mAb) therapy, the mechanisms of action by which such mAb mediate their anti-tumor effects are not completely understood. This includes a need to better understand the role of various NK cell subtypes and checkpoint molecules in anti-CD20 mAb therapy. Experimental procedures: Raji B cell lymphoma cells and peripheral blood mononuclear cells (PBMCs) from normal donors (n=21) were co-cultured with rituximab (RTX) or trastuzumab as a control mAb for up to 15 days. Analysis included assessment of proliferation, remaining viable cells and phenotype of various cell types. Results: As expected, RTX was superior to trastuzumab in eliminating Raji cells. RTX also induced proliferation of NK cells and a shift of NK cells from a CD56dim to CD56bright population. Both NK cell proliferation and the increase in the CD56bright population occurred at day 5-7 when elimination of Raji cells was largely complete. Addback of additional Raji cells at day 5 delayed proliferation of NK cells and the shift from a CD56dim to CD56bright population suggesting this shift occurs once activation of the NK cell via Fcγ;;R is complete. Evaluation of checkpoint molecule expression by NK cells demonstrated RTX, in the presence of Raji target cells, upregulates NK cell expression of TIGIT and TIM3, but not PD1, CTLA-4, or LAG-3. This upregulation was maintained for the full duration of incubation (up to 15 days). The level of expression of TIGIT and TIM3 on NK cells induced by RTX was dose dependent and peaked at 1-5 ug/ml. NK cells induced by RTX to express TIGIT or TIM3 degranulated (CD107a), produced cytokines (IFNγ, TNFα) and expressed activation markers (CD69 and CD25) to a greater degree than did TIGIT or TIM3 negative NK cells. Anti- TIGIT mAb enhanced CD107a expression and TNFα production by RTX-activated NK cells. Conclusion: NK cells proliferate and shift from CD56dim to CD56bright population after being activated and eliminating RTX-coated target cells. TIGIT and TIM3 are biomarkers for RTX-mediated NK cell activation. Blocking TIGIT can enhance RTX-mediated NK cell degranulation and cytokine production. Citation Format: Zhaoming Wang, George J. Weiner. The role of checkpoints in Rituximab-mediated NK cell activation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 909.

Targeting an adenosine-mediated "don't eat me signal" augments anti-lymphoma immunity by anti-CD20 monoclonal antibody.

A growing body of evidence suggests that macrophage immune checkpoint molecules are potential targets in the era of cancer immunotherapy. Here we showed that extracellular adenosine, an abundant metabolite in the tumor microenvironment, critically impedes the therapeutic efficacy of anti-CD20 monoclonal antibodies (mAbs) against B-cell lymphoma. Using a syngeneic B-cell lymphoma model, we showed that host deficiency of adenosine 2A receptor (A2AR), but not A2BR, remarkably improved lymphoma control by anti-CD20 mAb therapy. Conditional deletion of A2AR in myeloid cells, and to a lesser extent in NK cells, augmented therapeutic efficacy of anti-CD20 mAb. Indeed, adenosine signaling impaired antibody-mediated cellular phagocytosis (ADCP) by macrophages and limited the generation of anti-lymphoma CD8+ T cells. Pharmacological inhibition of A2AR overcame the adenosine-mediated negative regulation of ADCP by rituximab in a xeno-transplanted lymphoma model. Moreover, aberrant overexpression of CD39, an apical ecto-enzyme for adenosine generation, showed a negative impact on prognosis in patients with diffuse large B-cell lymphoma, as well as on preclinical efficacy of rituximab. Together, adenosine acts as a "don't eat me signal", and may be a potential target to harness anti-lymphoma immunity.

Anti-CD20 Therapy Reliance on Antibody-Dependent Cellular Phagocytosis Affects Combination Drug Choice

The efficacy of many therapeutic unconjugated monoclonal antibodies (mAbs), including those targeting CD20 in CLL, requires immune cell-mediated cytotoxicity. mAbs have often been optimized for natural killer (NK) cell antibody-dependent cellular cytotoxicity (ADCC) activity. However, in vivo mouse studies have shown that antibody-dependent cellular phagocytosis (ADCP) by macrophages is the major mechanism of clearance of circulating B cells by anti-CD20 mAbs. To directly compare ADCC versus ADCP, we previously used a panel of anti-CD20 mAbs (rituximab, ofatumumab, obinutuzimab, ocaratuzumab) to test cytotoxicity of paired human NK cells and monocyte-derived macrophages (hMDM) against CLL cells in vitro. All mAbs demonstrated ADCP activity at least 10-fold greater than ADCC as measured by CLL cell depletion per effector cell. Moreover, ADCC and ADCP activity levels did not correlate, meaning that ADCC cannot be used as a surrogate measure of ADCP for these mAb. This could explain why mAb optimization for ADCC activity has often failed to translate into more efficacious treatment. Thus, ADCP may be an effective translational measurement of anti-CD20 mAb performance. Because of the clinical interest in combining anti-CD20 mAb with targeted small molecule inhibitors, we began studying the effects of the Bruton tyrosine kinase (BTK) inhibitors on anti-CD20 mAb-mediated ADCP. Our initial studies showed that ibrutinib (IBR), but not acalabrutinib (Acala), significantly decreased anti-CD20 ADCP as measured by a flow cytometry-based assay that measures single timepoint cell collections. These types of assays cannot easily determine the kinetics and individual effector cell activity of ADCP. Thus, to more fully study the BTK inhibitor effects on ADCP, we developed a live cell time-lapse imaging method for measuring ADCP, utilizing recent advances in microscopy, cellular dye labeling, digital imaging, imaging software and computing. Whole-cell labeling of macrophages enabled visualization of internalized CLL cells as regions of dye exclusion or "voids". Because of the vast number of images acquired during live cell time-lapse imaging, we utilized computer software-aided image recognition and enumeration to measure the number of macrophages and voids inside each macrophage. As a measure of phagocytic engulfment, we developed a void index, which provides a relative measure of phagocytic engulfment per macrophage. Measuring ADCP in this manner replicates clinical observation of mAb therapeutic activity. Clinically, intravenous anti-CD20 mAb therapy typically induces a rapid decrease in circulating CLL cells (within hours), followed by a long period (days) of stable to increased levels of circulating cells. Similarly, our live cell time-lapse video assay shows initial rapid ADCP over the first 2 hours followed by a prolonged period of "hypophagia" with little ADCP for the remainder of the assay (imaged every 2 minutes for 8 hours). This "hypophagia" phenomenon may explain the resistance to therapeutic mAb observed clinically. With these new tools for quantitation of ADCP, we compared the effects of serial dilutions of IBR or Acala on ADCP. Overall, as measured by Area Under the Curve (AUC) analysis, IBR decreased phagocytic capacity of anti-CD20 mediated CLL cell ADCP at concentrations of 0.41 μM and above. By contrast, Acala did not begin to decrease AUC measurements until 3.7 μM, and subsequent AUC values were higher in Acala versus IBR-treated ADCP assays up to the highest tested drug concentration (100 μM). Similarly, the initial ADCP kinetics (void index / min over the first hour) reflected a decrease with IBR treatment at 0.41 μM that continued until a nadir was reached at 33 μM. In contrast, Acala did not induce a decrease in this kinetic measurement until 3.7 μM and a nadir was not reached (up to 100 μM). Thus, IBR significantly decreases ADCP by hMDM at concentrations much lower than a more specific BTK inhibitor, Acala. This result suggests that BTK inhibition has little to no effect on ADCP and furthermore suggests that IBR off-target effects decrease ADCP. IBR off-target candidates include other tyrosine kinases in the TEC (tyrosine kinase expressed in hepatocellular carcinoma) family. These data suggest that a a highly selective BTK inhibitor with little effect on ADCP could be a more suitable drug to combine with therapeutic mAb(s). Disclosures Chu: Pfizer: Equity Ownership; Acerta Pharma: Research Funding. VanDerMeid:AstraZeneca: Research Funding. Izumi:Acerta Pharma: Employment, Equity Ownership, Patents &amp; Royalties: Acalabrutinib patents; AstraZeneca: Equity Ownership. Munugalavadla:Acerta Pharma: Employment; AstraZeneca, Gilead Sciences: Equity Ownership. Barr:TG Therapeutics: Consultancy, Research Funding; Celgene: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; Seattle Genetics: Consultancy; Merck: Consultancy; Genentech: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Astra Zeneca: Consultancy, Research Funding; Janssen: Consultancy; AbbVie: Consultancy. Elliott:Astra Zeneca: Research Funding. Zent:Mentrik Biotech: Research Funding; Astra Zeneca: Research Funding.

Abstract A003: Safety and preliminary efficacy of ACTR707, autologous T lymphocytes expressing an antibody-coupled T-cell receptor, in combination with rituximab in subjects with relapsed or refractory CD20-positive B-cell lymphoma

Abstract Background: Autologous T cells engineered to express a universal ACTR chimeric receptor kill tumors through interactions with tumor-targeting antibodies [Kudo, Cancer Res 2014]. ACTR707 was identified through rigorous preclinical screening of more than 100 different ACTR variants. It is composed of the extracellular domain of CD16, the cytoplasmic signaling domain of CD3ζ, and the costimulatory domain of CD28. Study ATTCK-20-03 (NCT03189836) is the first clinical trial of ACTR707. ACTR707 in combination with rituximab is being studied in subjects with relapsed or refractory CD20+ B-cell lymphoma previously treated with anti-CD20 monoclonal antibody (mAb) therapy. Herein we report data from the first dose level of ACTR707, where 6 subjects have been enrolled and treated.Methods: ATTCK-20-03 is a first-in-human, multicenter phase 1 dose escalation study of ACTR707 in combination with rituximab. The primary objective is to evaluate the safety of ACTR707 in combination with rituximab, and secondary objectives include evaluation of antitumor activity, assessment of T-cell expansion and persistence, cytokine levels, and rituximab pharmacokinetics. Eligible subjects must have histologically confirmed relapsed or refractory aggressive CD20+ B-cell lymphoma of DLBCL, MCL, PMBCL, Gr3b FL, or transformed FL subtype and have received prior anti-CD20 mAb therapy in combination with chemotherapy. Subjects received lymphodepleting chemotherapy (cyclophosphamide 400 mg/m2 and fludarabine 30 mg/m2) for 3 days, followed by rituximab (375 mg/m2) and a single infusion of ACTR707. Additional doses of rituximab are administered, one dose every 3 weeks in the absence of disease progression. The study is separated into two sequential phases, a dose escalation and a safety expansion phase. During dose escalation, ACTR707 will be tested at increasing doses in combination with rituximab. Results: Six subjects received ACTR707 in combination with rituximab at the first dose level: 5 diagnosed with DLBCL (83%) and 1 with Gr3b FL (17%). Median age was 61 years (range: 57-76), 83% were male, 50% were treated with ≥ 3 lines of prior therapy, and 67% had no response to or progression within 6 months of immediate prior therapy. ACTR707 was successfully manufactured for all subjects. ACTR+ T cells demonstrated expansion and were detectable at D28 post-ACTR707 infusion for all subjects tested. There were no dose-limiting toxicities observed in the 4 subjects evaluable for DLTs (2 subjects were not DLT-evaluable due to early disease progression). There were no serious adverse events of cytokine release syndrome, neurotoxicity, or autoimmune events and no deaths on study. Grade 3 or higher AEs included neutropenia (n=2), febrile neutropenia (n=2), and thrombocytopenia (n=1). Antitumor activity was assessed in all 6 subjects. Three subjects experienced disease progression and 3 subjects demonstrated investigator-reported complete responses at the first disease response assessment (D42). Responses are ongoing at the time of the data cut-off. Conclusions: In the first dose level studied in subjects with relapsed or refractory aggressive CD20+ B-cell lymphoma, ACTR707 in combination with rituximab induced complete responses in 3 out of 6 treated subjects, with no serious events of cytokine release syndrome or neurotoxicity. ACTR+ T-cells were detectable in all subjects and ACTR+ T-cells persisted in the presence of continued rituximab administration. These results support the continued dose escalation of ACTR707 in combination with rituximab. Citation Format: Veronika Bachanova, Jonathon Cohen, Luke Akard, Samantha Jaglowski, Jessica Sachs, Ann Ranger, Patricia Harris, Kathleen McGinness, Greg Motz, Ian Flinn. Safety and preliminary efficacy of ACTR707, autologous T lymphocytes expressing an antibody-coupled T-cell receptor, in combination with rituximab in subjects with relapsed or refractory CD20-positive B-cell lymphoma [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A003.

Abstract CT146: First-in-human phase I combination of the IL-15 receptor super agonist complex ALT-803 with a therapeutic (anti-CD20) monoclonal antibody (mAb) for patients with relapsed or refractory indolent non-Hodgkin lymphoma (iNHL)

Abstract Immunotherapy is an effective modality for cancer treatment. IL-15 is a cytokine that stimulates CD8+ T cell and NK cell survival, metabolism, and anti-tumor immunity. We hypothesized that IL-15 therapy will augment anti-cancer immune responses in concert with tumor-targeting therapeutic mAbs. Pre-clinical studies have shown that the IL-15 receptor super agonist complex, ALT-803, enhanced the anti-tumor effects of anti-CD20 mAb against iNHL in vitro and in vivo (Rosario M et al., Clin Ca Res, 2016). Here, we conducted the first clinical study combining ALT-803 with a tumor-targeting mAb, in patients with rel/ref iNHL. A total of 21 iNHL patients [N=16 FL (FLIPI low: 4, int: 4, high: 8), N=4 MZL, N=1 SLL] were treated. Median age was 64 years (range 54-81), median number of prior therapies was 2 (range 1-18), and 5 patients were refractory to prior anti-CD20 mAb therapy. Treatment included an induction cycle of 4 weekly doses of rituximab (375 mg/m2 intravenously, IV) and ALT-803. The ALT-803 dose levels were 1, 3, and 6 mcg/kg IV followed by 6, 10, 15, and 20 mcg/kg subcutaneously (SC, N=3 per dose level). In patients with SD, PR or CR, consolidation therapy with ALT-803 (at the same dose level) and rituximab was then administered every 8 weeks for 4 cycles. No dose limiting toxicities were observed, and the recommended phase 2 dose was 20 mcg/kg SC. Overall ALT-803 was well tolerated with no grade 4 or 5 adverse events. Grade 3 AEs (regardless of attribution to ALT-803) included transient hypertension (14%), anemia (5%), nausea (5%), chills (5%), fever (5%), neutropenia (5%), and hyperglycemia (5%). Patients who received ALT-803 SC had a self-limited injection site reaction. To date, best ORR was 10/21 (48%), with 7 CR, 3 PR, 8 SD (all with decreased tumor volume), and 3 PD. Of the 12 patients treated with SC ALT-803, only 1 patient had PD, with the remainder receiving ongoing consolidation. In the 5 rituximab-refractory patients we observed 1 CR, 2 SD (45% and 36% tumor volume decrease), and 2 PD. PK analysis showed that SC ALT-803 administration resulted in a lower Cmax and prolonged blood levels compared to IV. At the 15 and 20 mcg/kg SC dose levels of ALT-803, NK cells were significantly increased by percentage (mean peak 30+5%, 6-fold, P&amp;lt;0.001) and number (mean peak 687+347/uL, 10-fold, P&amp;lt;0.001). This was accompanied by a marked increase in proliferation (Ki67, 97+0.5%, P&amp;lt;0.001) and activation (CD69, 10-fold, P&amp;lt;0.01) in vivo. CD8+ T cell number (2-fold, P&amp;lt;0.01) and proliferation (Ki67, 56+6%, P&amp;lt;0.001) were also significantly increased, without increases in CD4+ or regulatory T cell numbers. Patient NK cells exhibited enhanced functional responses (degranulation and IFN-γ production) against anti-CD20 mAb coated NHL targets after ALT-803 administration, compared to pre-ALT-803 samples. NK cells (P&amp;lt;0.05) and CD8 T cells (P&amp;lt;0.05) were also increased at the 6 and 10 mcg/kg SC ALT-803 levels. Thus, the immunostimulatory IL-15-based agent ALT-803 may be safely combined with a therapeutic mAb to significantly enhance NK and CD8+ T cell number and function in patients with iNHL. Phase 2 testing is underway in iNHL. Clinical investigations combining ALT-803 with additional therapeutic mAbs, complementary types of immunotherapy, and in additional malignancies are warranted. Citation Format: Todd A. Fehniger, Brian T. Hess, Veronika Bachanova, Michelle Becker-Hapak, Ethan McClain, Melissa Berrien-Elliott, Julia Wagner, Nancy L. Bartlett, Brad Kahl, Neha Mehta-Shah, Amanda F. Cashen, Feng Gao, Kyle Conradi, Amy D. Rock, Emily K. Jeng, Liza Hernandez, Jack O. Egan, Peter R. Rhode, Hing C. Wong. First-in-human phase I combination of the IL-15 receptor super agonist complex ALT-803 with a therapeutic (anti-CD20) monoclonal antibody (mAb) for patients with relapsed or refractory indolent non-Hodgkin lymphoma (iNHL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT146.

Next-generation anti-CD20 monoclonal antibodies in autoimmune disease treatment

The clinical success of anti-CD20 monoclonal antibody (mAb)-mediated B cell depletion therapy has contributed to the understanding of B cells as major players in several autoimmune diseases. The first therapeutic anti-CD20 mAb, rituximab, is a murine–human chimera to which many patients develop antibodies and/or experience infusion-related reactions. A second generation of anti-CD20 mAbs has been designed to be more effective, better tolerated, and of lower immunogenicity. These include the humanized versions: ocrelizumab, obinutuzumab, and veltuzumab, and the fully human, ofatumumab. We conducted a literature search of relevant randomized clinical trials in the PubMed database and ongoing trials in Clinicaltrials.gov. Most of these trials have evaluated intravenous ocrelizumab or subcutaneous ofatumumab in rheumatoid arthritis, multiple sclerosis, or systemic lupus erythematosus. Understanding how newer anti-CD20 mAbs compare with rituximab in terms of efficacy, safety, convenience, and cost is important for guiding future management of anti-CD20 mAb therapy in autoimmune diseases.

PI3Kδ Inhibition Elicits Anti-Leukemic Effects through Bim-Dependent Apoptosis

Introduction: Phosphatidylinositol-3-kinase δ (PI3Kδ)-signaling provides key maintenance, proliferation, and survival cues during both normal and malignant B-lymphocyte development. Consequently, isoform-selective PI3Kδ inhibitors (PI3Kδi) have generated huge interest as a potential treatment for lymphoid malignancies. In particular, PI3Kδi demonstrate impressive clinical efficacy in combination with anti-CD20 monoclonal antibodies (mAbs) for relapsed chronic lymphocytic leukemia (CLL). However, these combinations function primarily to delay disease progression, but are not curative. With the ever-rising number of new targeted therapeutics, the challenge is to identify combinations that will ultimately deliver curative regimes. In order to guide these selections, a detailed mechanistic understanding is required. To date, only limited data are available regarding the exact in vivo therapeutic mechanism of PI3Kδi. Currently, studies identify immunomodulation, inhibition of BCR-, chemokine/cytokine-signaling, and induction of apoptosis as putative therapeutic mechanisms. Here we characterize the molecular mechanisms responsible for PI3Kδi-induced cytotoxicity and determine the relative contribution toward in vivo therapeutic responses utilizing the Eµ-TCL1-Tg mouse model of CLL alongside human CLL samples.Methods: The molecular mechanisms of PI3Kδi alone or in combination with anti-CD20 mAbs were assessed using the Eµ-TCL1-Tg mouse model, an in vivo model system of CLL. To inhibit PI3Kδ, the δ isoform-selective inhibitor GS-9820 was chosen, as it is highly structurally related to idelalisib, and critically demonstrates improved pharmacokinetic properties in the mouse in comparison to idelalisib. In vitro GS-9820 IC50 are as follows: PI3Kδ 27 nM; PI3Kα 83,424 nM; PI3Kβ 14,899 nM; and PI3Kγ 15,606 nM. Assays to measure its effects on BCR-mediated kinase activation, chemokine signaling/chemotaxis, and cytokine- and cell-mediated support were performed. GS-9820 was administered in vivo at 10 mg/kg per os BID (formulated in 0.5% methylcellulose, 0.05% tween-80), once leukemias were detected, and maintained throughout the treatment period (GS-9820 Cmax 3114 nM, Ctrough 48.6 nM).Results: GS-9820 induced substantive in vitro cell death and disruptedBCR-mediated kinase activation, chemokine signaling/chemotaxis, and inhibited both cytokine- and cell-mediated support in murine (Eµ-TCL1) and human CLL cells. In vivo administration of GS-9820 imparted significant therapeutic responses in Eµ-TCL1-bearing animals, reducing leukemic burden by 75% and splenic tumor deposits by 66% 4 weeks posttreatment. GS-9820 appeared well tolerated in recipient animals with no obvious toxicity apparent (e.g. weight loss or behavioral symptoms). When in combination with anti-CD20 mAbs, GS-9820 extended leukemia depletion by several weeks. GS-9820 enhanced overall survival by 66% in comparison with vehicle control-recipient animals and enhanced the survival benefit of anti-CD20 mAb therapy. These therapeutic responses were associated with a 2-fold increase in expression of the pro-apoptotic BH3-only Bcl-2 family member Bim and a 3-fold increase in the extent of Bim/Bcl-2 interaction. Accordingly, Bim-/- Eµ-TCL1-Tg leukaemias exhibited profound resistance to PI3Kδi-induced cytotoxicity, were refractory to PI3Kδi in vivo, and failed to display combination efficacy with anti-CD20 mAbs. These findings informed the rational design of a GS-9820 + ABT199 (Venetoclax) complementary drug combination strategy. Combinations of GS-9820 and ABT199 were well tolerated with an absence of weight loss or altered behavioral symptoms. The GS-9820 + ABT199 combination effectively halted leukemia progression in vivo with increased efficacy compared to monotherapy regimes, resulting in a 90% reduction in leukemic burden at the end of the treatment period.Conclusions: Bim-dependent apoptosis represents the key in vivo effector mechanism for PI3Kδi in the Eµ-TCL1-Tg mouse model, both alone and in combination with anti-CD20 mAbs. As such, combinations of PI3Kδ and Bcl-2 inhibitors may represent an efficacious drug combination strategy. DisclosuresTannheimer:Gilead Sciences: Employment. Packham:Karus Therapeutics: Other: Share Holder & Founder; Aquinox Pharmaceuticals: Research Funding. Cragg:Baxalta: Consultancy; Roche: Consultancy, Research Funding; Bioinvent International: Consultancy, Research Funding; Gilead Sciences: Research Funding; GSK: Research Funding.

Abstract 1490: Potentiating immunotherapy by targeting complement deposited on cancer cell surfaces

Abstract Treatment of lymphoid malignancies with anti-CD20 antibodies (mAbs) can be frustrated by the loss of cell surface CD20 through trogocytosis, creating “escape variants” that are no longer sensitive to the anti-CD20 mAb. In patients with chronic lymphocytic leukemia (CLL) treated with the anti-CD20 mAb ofatumumab, we observed that these CD20 escape variants carried covalently bound C3d complement fragments and that these C3d opsonized CLL cells persisted for weeks in circulation. Therefore, we hypothesized that C3d is a neoantigen that could be exploited to re-target cells that have escaped from anti-CD20 mAb therapy. To target complement opsonized cells we generated a human IgG1 mouse chimera mAb specific to C3d that is not competed by full length C3 in serum. To test whether targeting C3d can eliminate escape variants after anti-CD20 therapy, we collected blood samples from CLL patients before (day 1) and 24 hours after administration of ofatumumab (day 2). As expected, CLL cells on day 2 had lost CD20 expression and could neither bind, nor be killed by ofatumumab. In contrast, the anti-C3d mAb did not bind CLL cells obtained pre-treatment but bound cells obtained on day 2 with high affinity (kD = 6.7nM) and were effectively killed through CDC, NK cell mediated ADCC, and phagocytosis. Importantly, non B lymphocytes were neither bound nor killed by the anti-C3d mAb, consistent with the highly targeted and selective deposition of C3d on CD20+ cells by ofatumumab. Interestingly, when C3d opsonized CLL was exposed repetitively to anti-C3d mAb ex vivo, the amount of cell bound C3d and the fraction of cells killed increased with successive rounds of treatment consistent with an auto-amplification of C3d targeting. We tested the efficacy of a chimerized anti-C3d mAb in two mouse models. First, we transferred PBMCs obtained from CLL patients on day 2 of ofatumumab treatment (containing the C3d opsonized CD20 escape variants) into NSG mice and three days later injected either isotype control mAb (trastuzumab) or anti-C3d mAb. One injection of anti-C3d mAb effectively reduced tumor burden in both peripheral blood (from 42.5 to 0.59 CLL cells/ul of blood; p&amp;lt;0.01) and spleen (from 574 to 2.19 CLL cells/100,000 splenocytes; p&amp;lt;0.01). Second, we subcutaneously xenografted HBL2 cells, a CD20+ mantle cell lymphoma line, into SCID mice. Mice were treated three days after cell injection with ofatumumab alone, ofatumumab and anti-C3d mAb or isotype control (trastuzumab). Caliper measurements of the tumor dimensions and survival were recorded. The combination of the anti-C3d mAb with ofatumumab extended time to tumor development and prolonged overall survival compared to ofatumumab alone (median survival 88 days vs 22 days, respectively, p&amp;lt;0.02). We conclude that targeting C3d deposited on cancer cells can eliminate antigen escape variants and potentiate complement fixing antibodies. Citation Format: Elizabeth J. Carstens, Martin Skarzynski, Vicent Butera, Margaret Lindorfer, Berengere Vire, Mohammed Farooqui, Christoph Rader, Ronald Taylor, Adrian Wiestner. Potentiating immunotherapy by targeting complement deposited on cancer cell surfaces. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1490.

Anti-CD20 monoclonal antibodies in chronic lymphocytic leukemia: from uncertainties to promises.

Over the last two decades, anti-CD20 monoclonal antibody (mAb) therapy has improved patient outcome in B-cell malignancies, and confirmed CD20 as an important target in chronic lymphocytic leukemia (CLL). Until recently, the gold standard was based on the utilization of rituximab combined with chemotherapy (fludarabine and cyclophosphamide), but patients often relapse. Next, with our better understanding of mAb engineering, anti-CD20 mAb therapy has evolved with the development of new mAb permitting significant clinical responses by improving pharmacokinetics, safety, activity and immunogenicity. Last but not least, the development of key tumoral tyrosine kinase inhibitors and their association with anti-CD20 mAb is a work in progress with promising results.

The IL-15-Based ALT-803 Complex Enhances FcγRIIIa-Triggered NK Cell Responses and In Vivo Clearance of B Cell Lymphomas.

Anti-CD20 monoclonal antibodies (mAb) are an important immunotherapy for B-cell lymphoma, and provide evidence that the immune system may be harnessed as an effective lymphoma treatment approach. ALT-803 is a superagonist IL-15 mutant and IL-15Rα-Fc fusion complex that activates the IL-15 receptor constitutively expressed on natural killer (NK) cells. We hypothesized that ALT-803 would enhance anti-CD20 mAb-directed NK-cell responses and antibody-dependent cellular cytotoxicity (ADCC). We tested this hypothesis by adding ALT-803 immunostimulation to anti-CD20 mAb triggering of NK cells in vitro and in vivo. Cell lines and primary human lymphoma cells were utilized as targets for primary human NK cells. Two complementary in vivo mouse models were used, which included human NK-cell xenografts in NOD/SCID-γc (-/-) mice. We demonstrate that short-term ALT-803 stimulation significantly increased degranulation, IFNγ production, and ADCC by human NK cells against B-cell lymphoma cell lines or primary follicular lymphoma cells. ALT-803 augmented cytotoxicity and the expression of granzyme B and perforin, providing one potential mechanism for this enhanced functionality. Moreover, in two distinct in vivo B-cell lymphoma models, the addition of ALT-803 to anti-CD20 mAb therapy resulted in significantly reduced tumor cell burden and increased survival. Long-term ALT-803 stimulation of human NK cells induced proliferation and NK-cell subset changes with preserved ADCC. ALT-803 represents a novel immunostimulatory drug that enhances NK-cell antilymphoma responses in vitro and in vivo, thereby supporting the clinical investigation of ALT-803 plus anti-CD20 mAbs in patients with indolent B-cell lymphoma.

A drug safety evaluation of rituximab and risk of hepatitis B

Introduction: Rituximab is a widely prescribed anti-CD20 mAb for the treatment of CD20+ B-cell non-Hodgkin Lymphoma and many other immune mediated conditions. There is a well-described association between rituximab containing chemo-immunotherapy treatment and reactivation of the hepatitis B virus (HBV). This review summarizes the current literature surrounding rituximab-associated HBV reactivation.Areas covered: Herein, we review the literature detailing the risk of HBV reactivation in inactive carriers and those with resolved hepatitis. The clinical presentation and management of HBV reactivation are also discussed along with a summary of clinical trials evaluating antiviral prophylaxis. Finally, clinical recommendations are detailed. Data from clinical trials, observational studies, reviews, and meta-analyses available in the Medline database were included in this narrative review.Expert opinion: Screening should be performed in all patients prior to the administration of any type of anti-CD20 mAb therapy. Among those with positive screening serology, testing for hepatitis B e antigen or viral load by polymerase chain reaction is appropriate. In those patients with detectable HBV DNA, the decision regarding the use of antiviral prophylaxis or observation should be individualized.