Casirivimab and Imdevimab (CAS + IMD) Antibody Combination for the Treatment of Immunocomprised Hospitalized Patients with COVID-19

Background. Immunocompromised (IC) individuals are at high risk for severe COVID-19, with high morbidity and mortality. CAS+IMD is a monoclonal antibody combination that neutralizes susceptible SARS-CoV-2 variants. We examined the natural history of COVID-19 and the efficacy and safety of CAS+IMD in IC patients (pts) hospitalized with COVID-19. Methods. In a phase 1/2/3 double-blind trial (NCT04426695) conducted Jun 2020 to Apr 2021, prior to the emergence of Omicron-lineage variants, hospitalized COVID-19 pts were randomized 1:1:1 to a single 2.4 g or 8.0 g dose (combined for analyses) of CAS+IMD or placebo (P). Post hoc analyses assessed change in viral load (VL), clinical outcomes (death or mechanical ventilation [MV]), and safety for IC pts with B-cell deficiency or dysfunction (Table 1) vs all pts. Results. 99/1940 (5.1%) treated pts were identified as IC (Table 2). At baseline, IC vs all pts were more likely to be seronegative for SARS-CoV-2 antibodies (68.7% vs 41.2%), and to have higher median VLs (7.21 vs 6.32 log10 copies/mL). Compared to all pts receiving P, IC pts receiving P had slower VL declines. Treatment with CAS +IMD led to a reduction in VL from baseline, with a least-squares mean timeweighted average change in VL difference vs P at Day 7 for IC pts of -0.69 (95% CI: -1.25, -0.41) vs -0.31 (CI: -0.42, -0.20) for all pts;treatment benefit persisted through Day 29 (Fig. 1). Although sample size was small for IC pts, trends in clinical outcomes of death or MV at Day 29 for IC pts (7/64 [11.0%] CAS+IMD vs 6/35 [17.2%] P) were consistent with those in all pts (200/1307 [15.3%] CAS+IMD vs 113/633 [17.9%] P). IC vs all pts treated with CAS+IMD exhibited similar rates of treatment emergent adverse events (TEAEs, 30.4% vs 26.6%), AEs of special interest (grade >=2 hypersensitivity or infusion-related reactions;1.4% vs 2.5%), and death (8.7% vs 12.2%;Table 3). IC and all pts exhibited fewer TEAEs with CAS+IMD vs P. Conclusion. IC vs all pts hospitalized with COVID-19 were more likely to exhibit high VLs at baseline and to be seronegative. In the study, a single dose of CAS+IMD significantly reduced VL in IC pts (for variants circulating at the time, predominantly Alpha) and resulted in fewer events of death or MV. There were no new safety findings in IC pts vs all study pts.

CASIRIVIMAB and IMDEVIMAB COMBINATION PROVIDES LONG-TERM PROTECTION AGAINST COVID-19

Background:A previous report showed that a single 1200 mg subcutaneous (SC) dose of casirivimab and imdevimab (cas/imd) prevented symptomatic COVID-19 by 81.4% and reduced all SARS-CoV-2 infections (symptomatic and asymptomatic) by 66.4% in household contacts living with recently infected individuals over a 28-day period. While highly effective vaccines now exist for the prevention of COVID-19, a significant unmet need remains in patients who are unable to mount or maintain an adequate immune response to vaccination. Here we present additional results from 7-month follow-up period of the aforementioned study. Methods: In this randomized, double-blind, placebo-controlled Phase III trial, asymptomatic participants exposed to a SARS-CoV-2-infected household member were randomized 1:1 to a single SC dose of placebo or 1200 mg cas/imd (600 mg of each monoclonal antibody). Efficacy analyses include participants who were RT-qPCR negative for SARS-CoV-2 (no current infection) and seronegative for SARS-CoV-2 (no prior infection) at baseline. The trial consisted of a primary efficacy assessment period of 28 days (Month 1) and a 7-month follow-up period (Months 2-8). Results: Results from 842 placebo and 841 cas/imd RT-qPCR negative/seronegative enrolled participants (data through 04Oct2021, prior to emergence of Omicron) are presented. During the entirety of the 8-month study, cas/imd reduced the risk of symptomatic SARS-CoV-2 infections by 81.2% versus placebo (nominal P<0.0001;Table) and all SARS-CoV-2 infections (symptomatic and asymptomatic) by 68.2% versus placebo (nominal P<0.0001;Table). During Months 2-5, the risk of symptomatic and all infections were reduced by 100% and 89.5%, respectively (nominal P<0.0001). During Months 6-8 there was a resumption of symptomatic and all SARS-CoV-2 infections in the cas/imd group (19.9%;nominal P=0.6411 and 30.7%;nominal P=0.3967 risk reduction, respectively). Fewer cas/imd participants had a medically-attended visit versus placebo during the 8-months (1/841 [0.1%] vs 16/842 [1.9%], respectively). No new safety signals were identified for cas/imd during the follow-up period. Conclusion: During the 8-month study period, a 1200 mg SC dose of cas/imd prevented SARS-CoV-2 infections, with maximal protection through Month 5. The prolonged protection supports the use of cas/imd for the long-term prevention of COVID-19 against susceptible variants, offering a pre-exposure prophylaxis strategy for individuals who are unlikely to respond or be protected by vaccination.

Casirivimab and Imdevimab for Treatment of Hospitalized Patients with COVID-19 Receiving Low Flow or No Supplemental Oxygen

Background. Casirivimab and imdevimab (CAS/IMDEV) is authorized for emergency use in the US for outpatients with COVID-19. We present results from patient cohorts receiving low flow or no supplemental oxygen at baseline from a phase 1/2/3, randomized, double-blinded, placebo (PBO)-controlled trial of CAS/IMDEV in hospitalized patients (pts) with COVID-19. Methods. Hospitalized COVID-19 pts were randomized 1:1:1 to 2.4 g or 8.0 g of IV CAS/IMDEV (co-administered) or PBO. Primary endpoints were time-weighted average (TWA) change in viral load from baseline (Day 1) to Day 7;proportion of pts who died or went on mechanical ventilation (MV) through Day 29. Safety was evaluated through Day 57. The study was terminated early due to low enrollment (no safety concerns). Results. Analysis was performed in pooled cohorts (low flow or no supplemental oxygen) as well as combined treatment doses (2.4 g and 8.0 g). The prespecified primary virologic analysis was in seronegative (seroneg) pts (combined dose group n=360;PBO n=160), where treatment with CAS/IMDEV led to a significant reduction in viral load from Day 1-7 (TWA change: LS mean (SE): -0.28 (0.12);95% CI: -0.51, -0.05;P=0.0172;Fig. 1). The primary clinical analysis had a strong positive trend, though it did not reach statistical significance (P=0.2048), and 4/6 clinical endpoints prespecified for hypothesis testing were nominally significant (Table 1). In seroneg pts, there was a 47.0% relative risk reduction (RRR) in the proportion of pts who died or went on MV from Day 1-29 (10.3% treated vs 19.4% PBO;nominal P=0.0061;Fig. 2). There was a 55.6% (6.7% treated vs 15.0% PBO;nominal P=0.0032) and 35.9% (7.3% treated vs 11.5% PBO;nominal P=0.0178) RRR in the prespecified secondary endpoint of mortality by Day 29 in seroneg pts and the overall population, respectively (Fig. 2). No harm was seen in seropositive patients, and no safety events of concern were identified. Conclusion. Co-administration of CAS/IMDEV led to a significant reduction in viral load in hospitalized, seroneg pts requiring low flow or no supplemental oxygen. In seroneg pts and the overall population, treatment also demonstrated clinically meaningful, nominally significant reductions in 28-day mortality and proportion of pts dying or requiring MV.

REGN5458, a BCMA x CD3 Bispecific Monoclonal Antibody, Induces Deep and Durable Responses in Patients with Relapsed/Refractory Multiple Myeloma (RRMM)

Background Multiple myeloma (MM) is characterized by expression of the cell surface protein B-cell maturation antigen (BCMA), a validated target for therapeutic intervention. REGN5458 is a BCMA x CD3 bispecific antibody (Ab) that binds to both BCMA and CD3, thereby targeting MM cells with T-cell effector function via BCMA. Previously, we presented data showing REGN5458 has an acceptable safety profile with evidence of clinical efficacy in heavily pre-treated patients with RRMM. Here we describe the updated safety and response durability in a Phase 1 trial of REGN5458 monotherapy in patients with RRMM (NCT03761108). Methods The primary objectives of the Phase 1 portion of the study are to determine the safety, tolerability, and occurrence of dose-limiting toxicities (DLTs) of REGN5458. Key secondary objectives include assessment of objective response rate (ORR), duration of response (DOR), minimum residual disease (MRD) status, pharmacokinetics (PK), and pharmacodynamics. Enrollment into the Phase 1 portion follows a standard 4+3 dose escalation design. Enrolled patients must have progressive MM after ≥3 prior lines of systemic therapy, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 Ab. Treatment consists of weekly doses of REGN5458, followed by a maintenance phase administered every 2 weeks. Response assessments are according to modified International Myeloma Working Group criteria. MRD is assessed by flow cytometry. Results As of the June 15, 2020 data cut-off, 45 patients were treated with REGN5458. The median age at enrollment was 64.0 years (range, 41−81), of which 14 (31.1%) patients were >70 years. As per Revised International Staging System, 60.0% and 22.2% of patients were stage 2 and 3, respectively. Patients had a median of 5.0 (range, 2−17) prior lines of systemic therapy;32 patients (71.1%) received a prior autologous stem cell transplant. All patients were refractory to an anti-CD38 Ab;6.7% were triple-refractory, 33.3% were quad-refractory, and 53.3% were penta-refractory. REGN5458 was escalated in cohorts from 3−96 mg over six dose levels. The median duration of follow-up was 2.37 months (range, 0.7−12.3). The most common treatment-related adverse events (TRAEs) include cytokine release syndrome (CRS;37.8%), fatigue (17.8%), nausea (17.8%), and myalgias (13.3%). CRS occurred primarily during the initial doses and was Grade (Gr) 1 in 88.2% of patients. No patients had Gr >3 CRS. Infusion-related reactions occurred in 6.7% of patients. Infection-related adverse events (AEs) occurred in 46.7% of patients (Gr ≥3 20%). Gr >3 treatment-related neurological events occurred in one patient (Gr 3 syncope 130 days after first infusion). Four patients discontinued due to AE with one patient having a TRAE (also DLT) of Gr 4 acute kidney injury. One patient had a DLT due to transient Gr 3 liver transaminases associated with CRS. Upon recovery, the patient continued study drug and has achieved ongoing partial remission. Gr >3 TRAEs occurred in 28.9% of patients, with the most common being anemia (8.9%) and lymphopenia (6.7%). Serious TRAEs occurred in 22.2% of patients, with the most common due to CRS (11.1%). Gr 5 AEs (all unrelated to study drug) occurred in three patients: two sepsis and one COVID-19. ORR was 35.6% across all dose levels (60% in highest dose level), with 81.3% of responders achieving at least a very good partial response;31.3% had a complete response (CR) or stringent CR. A total of 43.8% of responders had a DOR >4 months and 18.8% had a DOR >8 months. The ORR in patients with extramedullary plasmacytomas was 16.7%. Additional efficacy, PK, and biomarker data will be available at the time of presentation. Conclusions In this updated analysis of the first-in-human study, REGN5458 continues to show an acceptable safety profile and durable efficacy in heavily pre-treated patients with RRMM. Enrollment in the Phase 1 dose escalation portion is ongoing, and the Phase 2 portion of the study is recruiting. Disclosures: Madduri: Janssen: Consultancy, Honora ia;Foundation Medicine: Consultancy, Honoraria;Legend: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau;Kinevant: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau;GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau;AbbVie: Consultancy, Honoraria;Takeda: Consultancy, Honoraria;Celgene: Consultancy, Honoraria. Brayer: Janssen: Consultancy;Bristol-Myers Squibb, WindMIL Therapeutics: Research Funding;Bristol-Myers Squibb, Janssen, Amgen: Speakers Bureau. Zonder: Prothena: Consultancy;BMS: Consultancy, Research Funding;Caelum: Consultancy;Oncopeptide: Membership on an entity's Board of Directors or advisory committees, Other: Personal fees;Amgen: Membership on an entity's Board of Directors or advisory committees, Other: Personal fees;Janssen: Consultancy, Other: Personal fees;Alnylam: Membership on an entity's Board of Directors or advisory committees, Other: Personal fees;Intellia: Membership on an entity's Board of Directors or advisory committees, Other: Personal fees;Takeda: Membership on an entity's Board of Directors or advisory committees, Other: Personal fees;Celgene: Research Funding. Bensinger: Sanofi: Consultancy, Honoraria, Research Funding, Speakers Bureau;Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau;Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau;Regeneron Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees;GSK: Consultancy, Honoraria, Research Funding, Speakers Bureau;BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau. Li: Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Xu: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Adriaens: Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties: Dosing regime that mitigates cytokine release syndrome for therapeutic antibodies (status: pending). Chokshi: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Zhang: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Boyapati: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Sharma: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Seebach: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Sirulnik: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Weinreich: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Yancopoulos: Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Dhodapkar: Amgen: Membership on an entity's Board of Directors or advisory committees, Other;Kite: Membership on an entity's Board of Directors or advisory committees, Other;Janssen: Membership on an entity's Board of Directors or advisory committees, Other;Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Other;Roche/Genentech: Membership on an entity's Board of Directors or advisory committees, Other;Lava Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other. Lentzsch: Mesoblast: Divested equity in a private or publicly-traded company in the past 24 months;Caelum Biosciences: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees;Celularity: Consultancy, Other;Janssen: Consultancy;Karyopharm: Research Funding;Magenta: Current equity holder in private company. Jagannath: MS, Janssen, Karyopharm, Legend Biotech, Sanofi, Takeda: Consultancy. OffLabel Disclosure: The data described in the abstract will report on use of REGN5458 in a first-in-human trial in patients with multiple myeloma.

Casirivimab with imdevimab antibody cocktail for COVID-19 prevention: Interim results

Background: Passive immunization has a long history for infection prevention following exposure. We report results of a descriptive interim analysis from a study of an antibody “cocktail” of casirivimab with imdevimab (cas/imdev;formerly REGN-COV2) designed to bind non-competing epitopes of the viral spike protein, as a potential passive vaccine for the prevention of COVID-19 in people at risk of infection from household contact. Methods: In this ongoing Phase 3 study, asymptomatic participants exposed to a COVID-19-infected household member were randomized 1:1 to placebo or 1200 mg cas/imdev (600 mg of each antibody administered subcutaneously) within 96 hours of their household member testing positive. The analysis included participants who tested negative for SARS-CoV-2 by nasal, saliva, or nasopharyngeal swab and who were seronegative to SARS-CoV-2 antibodies at baseline. The proportion of participants who developed an RT-PCR-confirmed SARS-CoV-2 infection (asymptomatic or symptomatic) during the 1-month efficacy assessment period was summarized. Results: Initial results from the first evaluable 223 placebo and 186 cas/imdev participants who completed ≥29 days of the study are reported. Reduction in PCR-positive symptomatic disease was 100% (0/186 cas/imdev vs 8/223 placebo;OR 0.00 [CI 0.00, 0.69]). Reduction in any PCR-positive infection (symptomatic or asymptomatic) was 48% (10/186 vs 23/223;OR 0.49 [CI 0.20, 1.12]). Placebo-group participants had on average 100-fold higher peak viral load. In the cas/imdev group, viral RNA was not detected for longer than 1 week but was detected for 3-4 weeks in approximately 40% of placebo participants (Fig. 1). The proportions of infected participants with high viral loads (>10 4 copies/mL) were 13/21 placebo vs 0/9 cas/imdev. Total weeks of viral RNA detection and high viral load were 44 and 22 weeks in the placebo group vs 9 and 0 in the cas/imdev group. Total symptomatic weeks were 21 for placebo vs 0 for cas/imdev. A similar proportion of participants experienced at least 1 serious adverse event: placebo, 3/222 and cas/imdev, 1/186;none were deemed related to study treatment. Injection site reactions were similar: placebo, 1.4%;cas/ imdev, 2.6%. Conclusion: In this descriptive interim analysis of participants at risk of SARSCoV- 2 infection from household transmission, a subcutaneous dose of the cas/ imdev antibody cocktail prevented symptomatic infection, reduced overall infection, and decreased viral load and duration of viral RNA detection.