Administration Of mAb Research Articles

Development, Characterization, and in vivo Validation of a Humanized C6 Monoclonal Antibody that Inhibits the Membrane Attack Complex

Damage and disease of nerves activates the complement system. We demonstrated that activation of the terminal pathway of the complement system leads to the formation of the membrane attack complex (MAC) and delays regeneration in the peripheral nervous system. Animals deficient in the complement component C6 showed improved recovery after neuronal trauma. Thus, inhibitors of the MAC might be of therapeutic use in neurological disease. Here, we describe the development, structure, mode of action, and properties of a novel therapeutic monoclonal antibody, CP010, against C6 that prevents formation of the MAC in vivo. The monoclonal antibody is humanized and specific for C6 and binds to an epitope in the FIM1-2 domain of human and primate C6 with sub-nanomolar affinity. Using biophysical and structural studies, we show that the anti-C6 antibody prevents the interaction between C6 and C5/C5b by blocking the C6 FIM1-2:C5 C345c axis. Systemic administration of the anti-C6 mAb caused complete depletion of free C6 in circulation in transgenic rats expressing human C6 and thereby inhibited MAC formation. The antibody prevented disease in experimental autoimmune myasthenia gravis and ameliorated relapse in chronic relapsing experimental autoimmune encephalomyelitis in human C6 transgenic rats. CP010 is a promising complement C6 inhibitor that prevents MAC formation. Systemic administration of this C6 monoclonal antibody has therapeutic potential in the treatment of neuronal disease.

Impact of IgG Isotype on the Induction of Antibody-Dependent Cellular Phagocytosis of HIV by Human Milk Leukocytes.

Approximately 100,000 mother-to-child transmission (MTCT) events of HIV via human milk feeding occur each year. However, only about 15% of infants milk-fed by untreated HIV+ mothers become infected, suggesting a protective effect of the milk itself. Infants ingest 105-108 maternal leukocytes daily via milk, which remain functional beyond ingestion. Such function may be elicited by maternal milk antibody (Ab). Though IgA is dominant in milk, most HIV-specific milk Abs are of the IgG subclass, highlighting the importance of investigating the function of each IgG isotype in the milk context. Though Ab effector function mediated by the constant (Fc) domain via interaction with Fc Receptors (FcRs), such as Ab-dependent cellular phagocytosis (ADCP), are critical in protecting against HIV infection, ADCP is largely unexplored as it relates to mitigation of MTCT. Presently we report the ADCP activity of milk leukocytes against HIV particles and immune complexes (ICs), using 57 unique samples from 34 women, elicited by IgG1/2/3/4 of monoclonal (m)Ab 246-D. Granulocyte ADCP of HIV was most potent compared to other phagocytes when elicited by IgG1/3/4. IgG1/3 activated granulocytes similarly, exhibiting 1.6x-4.4x greater activity compared to IgG2/4, and a preference for virus compared to ICs. Notably, CD16- monocyte ADCP of a given target were unaffected by isotype, and CD16+ monocytes were poorly stimulated by IgG1. IgG2/4 elicited potent IC ADCP, and in terms of total leukocyte IC ADCP, IgG4 and IgG3 exhibited similar function, with IgG4 eliciting 1.6x-2.1x greater activity compared to IgG1/IgG2, and CD16+ monocytes most stimulated by IgG2. These data contribute to a more comprehensive understanding of Fc-mediated functionality of milk leukocytes, which is critical in order to develop therapeutic approaches to eliminating this route of MTCT, including mucosal administration of mAbs and/or a maternal vaccination aimed to elicit a potent milk Ab response.

Anti‐CD3 mAb Induced Necrotizing Enterocolitis in Formula‐Fed Neonatal Mice through a Gut Microbiome Colonization Dependent Mechanism

Necrotizing enterocolitis (NEC) is a serious disease that affects the small intestine of premature infants. Previous studies showed that formula feeding is a risk factor for NEC. Furthermore, gut microbiome and T cells are revealed to play a critical role in the pathogenesis of NEC. It has been reported that anti‐CD3 mAb induces T cell activation and small intestinal injury in adult mice. However, how the small intestine of neonatal mice responses to anti‐CD3 mAb treatment is uncertain. In the present study, we aimed to study the susceptibility of dam‐fed and formula‐fed neonatal mice to the anti‐CD3 mAb challenge. For this purpose, mouse pups (P0) were nursed by dam feeding (DF) and formula feeding (FF) respectively. On postnatal day 2, pups were subjected to subcutaneous treatment with 10 mg/kg anti‐CD3ε mAb. They were processed to measure intestinal permeability to FITC‐dextran and euthanized at 24 h after administration of anti‐CD3 mAb. Histology examination showed that FF but not DF pups developed NEC‐like injury in the small intestine after anti‐CD3 treatment. FF Pups were noted to display an increase in mortality, intestinal permeability, and inflammatory mediators upon anti‐CD3 mAb challenge compared to DF pups. Even though the inflammatory markers were increased, the intestinal mucosa in DF pups remains intact after being challenged with anti‐CD3. Remarkably, disruption of postnatal colonization by gavaging streptomycin attenuated NEC incidence in anti‐CD3 mAb‐treated FF pups, suggesting that bacterial colonization plays a role in predisposition of mouse pups by formula feeding to anti‐CD3 mAb‐induced intestinal injury. Taken together, this study provided the first evidence that anti‐CD3 mAb induces NEC‐like injury in neonatal mice receiving FF but not in DF via a microbiome colonization dependent manner. The underlying mechanisms regarding this pathophysiological event are to be studied in the future.

Pharmacology and pharmacokinetics of fentanyl toxicity reversal by anti‐fentanyl monoclonal antibodies in combination with naloxone

AIMWidespread access to illicit fentanyl has contributed to an ongoing epidemic of fatal drug overdoses in the United States. The incidence of fatal overdoses in the United States accelerated during the COVID‐19 pandemic, with over 100,000 deaths recorded by April 2021. Fentanyl‐specific monoclonal antibodies (mAb) offer a prophylactic and therapeutic intervention against opioid overdose by binding and sequestering fentanyl in serum, and reducing distribution to the brain. Here, the kinetics of overdose reversal by anti‐fentanyl mAb alone or in combination with naloxone were explored, and the dose‐response relationship between naloxone and high doses of fentanyl in the presence of mAb was evaluated.METHODSTo evaluate the kinetics of fentanyl reversal, fentanyl 0.1 mg/kg was administered to male Sprague‐Dawley rats, and mAb or naloxone was administered fifteen minutes after exposure. Oxygen saturation was monitored constantly for ten minutes following administration of reversal agent. To evaluate duration and extent of protection from further fentanyl exposures, rats were pre‐treated with mAb, naloxone, or a combination, and challenged with increasing doses of fentanyl up to 0.5 mg/kg. Finally, to determine whether the presence of mAb would increase efficacy of naloxone against a lethal dose of fentanyl, 2.25 mg/kg fentanyl was administered, followed by naloxone 0.01 to 1.0 mg/kg.RESULTSThe most rapid reversal of fentanyl toxicity was achieved by intravenous administration of a combination of anti‐fentanyl mAb and naloxone (<1 min). Intravenous naloxone reversed fentanyl toxicity more quickly than subcutaneous naloxone, and intravenous mAb was effective against fentanyl within 4 minutes, similar to subcutaneous NLX. Against further challenges of fentanyl, both mAb and 0.1 mg/kg naloxone were effective against 0.1‐0.2 mg/kg fentanyl, and the combination of mAb and naloxone was effective against doses of 0.5 mg/kg fentanyl or higher. Prophylactic administration of mAb enhanced efficacy of naloxone in reversing a potentially lethal challenge of 2.25 mg/kg fentanyl. Finally, mAb sequestered high concentrations of both fentanyl and its metabolite norfentanyl in serum, and reduced brain concentrations of fentanyl in pre‐exposure scenarios.CONCLUSIONSThese results support translation of mAb as medical countermeasures to prevent and reverse opioid overdose related to fentanyl and its analogs.

Anti-Gr-1 Antibody Provides Short-Term Depletion of MDSC in Lymphodepleted Mice with Active-Specific Melanoma Therapy.

Lymphodepletion, reconstitution and active-specific tumor cell vaccination (LRAST) enhances the induction of tumor-specific T cells in a murine melanoma model. Myeloid-derived suppressor cells (MDSC) may counteract the induction of tumor-reactive T cells and their therapeutic efficacy. Thus, the aim of the study was to evaluate a possible benefit of MDSC depletion using anti-Gr-1 antibodies (Ab) in combination with LRAST. Female C57BL/6 mice with 3 days established subcutaneous (s.c.) D5 melanoma were lymphodepleted with cyclophosphamide and reconstituted with naive splenocytes. Vaccination was performed with irradiated syngeneic mGM-CSF-secreting D5G6 melanoma cells. MDSC depletion was performed using anti-Gr-1 Ab (clone RB6-8C5). Induction of tumor-specific T cells derived from tumor vaccine draining lymph nodes (TVDLN) was evaluated by the amount of tumor-specific interferon (IFN)-γ release. LRAST combined with anti-Gr-1 mAb administration enhanced the induction of tumor-specific T cells in TVDLN capable of releasing IFN-γ in a tumor-specific manner. Additional anti-Gr-1 mAb administration in LRAST-treated mice delayed growth of D5 melanomas by two weeks. Furthermore, we elucidate the impact of anti-Gr-1-depleting antibodies on the memory T cell compartment. Our data indicate that standard of care treatment regimens against cancer can be improved by implementing agents, e.g., depleting antibodies, which target and eliminate MDSC.

Myelin-associated glycoprotein activation triggers glutamate uptake by oligodendrocytes in vitro and contributes to ameliorate glutamate-mediated toxicity in vivo.

Myelin-associated glycoprotein (MAG) is a key molecule involved in the nurturing effect of myelin on ensheathed axons. MAG also inhibits axon outgrowth after injury. In preclinical stroke models, administration of a function-blocking anti-MAG monoclonal antibody (mAb) aimed to improve axon regeneration demonstrated reduced lesion volumes and a rapid clinical improvement, suggesting a mechanism of immediate neuroprotection rather than enhanced axon regeneration. In addition, it has been reported that antibody-mediated crosslinking of MAG can protect oligodendrocytes (OLs) against glutamate (Glu) overload by unknown mechanisms. To unravel the molecular mechanisms underlying the protective effect of anti-MAG therapy with a focus on neuroprotection against Glu toxicity. MAG activation (via antibody crosslinking) triggered the clearance of extracellular Glu by its uptake into OLs via high affinity excitatory amino acid transporters. This resulted not only in protection of OLs but also nearby neurons. MAG activation led to a PKC-dependent activation of factor Nrf2 (nuclear-erythroid related factor-2) leading to antioxidant responses including increased mRNA expression of metabolic enzymes from the glutathione biosynthetic pathway and the regulatory chain of cystine/Glu antiporter system xc- increasing reduced glutathione (GSH), the main antioxidant in cells. The efficacy of early anti-MAG mAb administration was demonstrated in a preclinical model of excitotoxicity induced by intrastriatal Glu administration and extended to a model of Experimental Autoimmune Encephalitis showing axonal damage secondary to demyelination. MAG activation triggers Glu uptake into OLs under conditions of Glu overload and induces a robust protective antioxidant response.

Safety of Monoclonal Antibodies in Children Affected by SARS-CoV-2 Infection.

Monoclonal antibody therapies for COVID-19 have been frequently used in adults, whereas there are little data regarding the safety or efficacy of monoclonal antibody treatments in pediatric patients affected by COVID-19. We report our experience in the administration of mAb as a treatment for SARS-CoV-2 infection in children aged from 24 days to 18 years old.

Real-world evaluation of the impact of two anti-SARS-CoV-2 monoclonal antibody regimens on COVID-19 hospitalizations in older adults.

Evidence from clinical trials suggest anti‐SARS‐CoV‐2 monoclonal antibodies (mABs) may reduce coronavirus disease 2019 (COVID‐19)‐related hospitalizations. The purpose of this study was to assess the real‐world impact of mAB administration on COVID‐19 hospitalization among patients 65 years or older. This was a retrospective, propensity‐matched cohort study that included patients aged 65 years and older who presented to the emergency department (ED) within 10 days of symptom onset of mild to moderate COVID‐19 infection. Outcomes were compared between those who did and did not receive mAB therapy. The primary endpoint was the rate of hospitalization for COVID‐19 within 30 days of index ED visit. A total of 137 patients receiving mABs were matched to 137 controls. Hospitalization occurred in 2.9% of mAB‐treated patients compared to 14.6% of patients of the standard of care (SOC) arm (odds ratio: 0.20 [95% CI: 0.07–0.59]). There were zero intubations and zero deaths compared to 3 (2.2%) and 2 (1.5%) in the SOC group. Among the 223 patients receiving mAB in the overall cohort, adverse drug events occurred in 10 (4.5%). Treatment with mAB therapy for mild to moderate COVID‐19 was associated with a substantially reduced risk of hospitalization among patients at least 65 years of age.

Abstract P2-13-27: Infusion-related reactions in patients receiving pertuzumab and trastuzumab: A retrospective study

Abstract BACKGROUND: The use of two anti-HER2 monoclonal antibodies (mAbs) (pertuzumab and trastuzumab) combined with taxanes is the standard of care for first line treatment in HER2-positive metastatic breast cancer (mBC). Infusion related reactions (IRR) during first administration of anti-HER2 mAb have been reported. Reintroduction of the causal drugs is often possible, but there is no data to identify patients at highest risk of developing IRR and modalities of safe reintroduction. The aim of this study was to report patients who experienced IRR during anti-HER2 mAbs infusions at Institut Curie Hospitals (ICH) and to describe these reactions. METHODS: All IRR cases must be reported to the ICH pharmacies. We retrospectively inspected the electronic record of patients who experienced an IRR during pertuzumab (Pmab) and trastuzumab (Tmab). We collected patients’ characteristics, grade of IRR and outcomes. RESULTS: From January 2013 to December 2020, a total of 223 patients had at least one Pmab+Tmab infusion as part of their BC treatment. Among them, 28 patients (8%) with anti-HER2 mAb IRR were identified. All patients but one had an HER2-positive BC; the HER2-negative case was a HER3-mutant mBC. Twelve patients (43%) had de novo mBC. Twenty-six patients (93%) received Pmab+Tmab as first line treatment for mBC. Ten patients were previously exposed to Tmab and three to Pmab+Tmab for (neo)adjuvant treatment. At IRR onset, 21 patients (75%) had liver metastasis, with more than five liver metastases for 19 of them. Fifteen patients (55%) had liver enzymes upper normal limit. IRR occurred during first anti-HER2-mAb infusion in 22 patients (79%) despite pre-treatment with antihistaminic and/or glucosteroids for taxanes. The other IRR were reported at the 2nd, 5th, 6th, 8th and > 10th cycle of Pmab+Tmab. Sixteen IRR (57%) were attributed to Pmab infusion, 9 (32%) to Tmab infusion and 3 (11%) to Tmab and/or Pmab. Al IRR were declared to the pharmacovigilance agency. Majority of reactions were mild to moderate (54% of grade 2). Most frequent symptoms associated with IRR were: thrills (68%), hyperthermia (64%); low oxygen saturation (36%), pain (25%), hypotension (21%), cutaneous (18%) and digestive (18%) reaction. Three patients were transferred to ICU. One death was attributed to anti-HER2 mAb IRR (death was attributed to respiratory distress during the first Tmab infusion). Reintroduction off Pmab+Tmab was performed in 18 patients, after pre-treatment with antihistaminic and/or glucosteroids and with vital function monitoring in conventional hospitalization. No recurrence of IRR was observed in 15/18 patients. For the 3 patients with recurrent IRR, symptoms were mild to moderate. Objective response to anti-HER2 treatments was observed in twenty three patients (82%; 8 complete responses; 15 partial responses). Median PFS was 16 months. CONCLUSIONS: Most anti-Her2-mAb IRR occurs during first infusion, are mild to moderate and do not require a transfer in ICU. Our study suggests that patients with high liver burden might be over-represented among those experiencing an IRR. Reintroduction of Pmab+Tmab was safe in most patients, allowing the continuation of the anti-HER2 dual blockade. Citation Format: Delphine Loirat, Juliette Logeart, Pauline Vaflard, Aurélien Noret, Mathilde Saint-Ghislain, Edith Borcoman, Audrey Hurgon, Cyrille Cros, Thomas Genevee, Audrey Bellesoeur, Francesco Ricci, Florence Lerebours, Laurence Escalup, Marie-Paule Sablin, François-Clément Bidard, Paul H. Cottu, Jean-Yves Pierga. Infusion-related reactions in patients receiving pertuzumab and trastuzumab: A retrospective study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-27.

Comparative Efficacy of Early COVID-19 Monoclonal Antibody Therapies: A Retrospective Analysis.

BackgroundBamlanivimab and casirivimab/imdevimab are monoclonal antibody (mAb) treatments used for mild to moderate coronavirus disease 2019 (COVID-19) in high-risk patients. To date, there are few data summarizing real-world evidence comparing the 2 mAbs. Additionally, there are insufficient data to guide administration timing relative to symptom onset. The purpose of this study was to evaluate 30-day failure rates for each agent and to identify the relationship between symptom onset and efficacy.MethodsWe performed a retrospective cohort study of a 6-month period at a large community medical center. Consecutive outpatients diagnosed with COVID-19 disease by nasopharyngeal (NP) polymerase chain reaction (PCR) testing received either bamlanivimab 700 mg or casirivimab/imdevimab 1200 mg/1200 mg. Each patient was followed for a total of 30 days. Three independent, blinded physicians performed adjudication for revisit reasons. The primary outcome was therapy-related failure, defined as COVID-19-related hospital admission within 30 days of infusion. Multivariable logistic regression was performed to adjust for confounders that may have influenced hospital admission in either group.ResultsDuring the period from November 2020 to May 2021, 183 patients were treated with bamlanivimab and 270 with casirivimab/imdevimab. The mean age was ~67 years and body mass index 30 kg/m2. Thirty-day admission for therapy-related failure rates were 4.8% and 13.7% for casirivimab/imdevimab and bamlanivimab, respectively (P = .001). No significant differences were found between early (<3 days of symptom onset) and late administration of either mAb.ConclusionsThere was a higher failure rate with bamlanivimab vs casirivimab/imdevimab. No difference in efficacy was found between early vs late administration of either mAb.

Pharmacological Profiling of Antifentanyl Monoclonal Antibodies in Combination with Naloxone in Pre- and Postexposure Models of Fentanyl Toxicity.

The incidence of fatal drug overdoses in the United States is an alarming public health threat that has been exacerbated by the COVID-19 pandemic, resulting in over 100,000 deaths between April 2020 and April 2021. A significant portion of this is attributable to widespread access to fentanyl and other synthetic opioids, alone or in combination with heroin or psychostimulants, such as cocaine or methamphetamine. Monoclonal antibodies (mAb) offer prophylactic and therapeutic interventions against opioid overdose by binding opioids in serum, reducing distribution of drug to the brain and other organs. Here, we investigated the efficacy of a leading antifentanyl mAb, clone HY6-F9, in reversal and prevention of fentanyl-induced toxicity compared with the opioid receptor antagonist naloxone (NLX) in rats. In postexposure models, rats were challenged with fentanyl, followed by HY6-F9, NLX, or both. HY6-F9 reversed fentanyl-induced antinociception, respiratory depression, and bradycardia, and rats retained protection against additional challenges for at least 1 week. Although intravenous NLX reversed fentanyl-induced respiratory depression more rapidly than mAb alone, kinetics of reversal by intravenous mAb were similar to subcutaneous NLX. Coadministration of mAb and NLX provided greater protection than individual treatments against high doses of fentanyl. Prophylactic administration of mAb reduced the ED50 of NLX approximately twofold against 2.25 mg/kg of fentanyl. Finally, mAb sequestered fentanyl and its metabolite norfentanyl in serum and reduced brain concentrations of fentanyl. These results support the translation of mAb as medical interventions alone or in combination with NLX to prevent and reverse fentanyl-related overdose. SIGNIFICANCE STATEMENT: Fentanyl-related overdoses have increased dramatically in the US and worldwide. Currently, approved pharmacotherapies for treatment of opioid use disorder and reversal of overdose are not sufficient to curb the incidence of opioid-related deaths. Additionally, fentanyl and its potent analogs present a potential risk from use in deliberate poisoning or chemical attacks. This study demonstrates the use of monoclonal antibodies as a countermeasure to fentanyl-induced toxicity in pre- and postexposure scenarios, supporting their use in combination with the opioid antagonist naloxone.

Integrin α5 mediates cancer cell-fibroblast adhesion and peritoneal dissemination of diffuse-type gastric carcinoma.

Diffuse-type gastric carcinoma (DGC) has a poor prognosis due to its rapid diffusive infiltration and frequent peritoneal dissemination. DGC is associated with massive fibrosis caused by aberrant proliferation of cancer-associated fibroblasts (CAFs). Previously, we reported that direct heterocellular interaction between cancer cells and CAFs is important for the peritoneal dissemination of DGC. In this study, we aimed to identify and target the molecules that mediate such heterocellular interactions. Monoclonal antibodies (mAbs) against intact DGC cells were generated and subjected to high-throughput screening to obtain several mAbs that inhibit the adhesion of DGC cells to CAFs. Immunoprecipitation and mass spectrometry revealed that all mAbs recognized integrin α5 complexed with integrin β1. Blocking integrin α5 in DGC cells or fibronectin, a ligand of integrin α5β1, deposited on CAFs abrogated the heterocellular interaction. Administration of mAbs or knockout of integrin α5 in DGC cells suppressed their invasion led by CAFs in vitro and peritoneal dissemination in a mouse xenograft model. Altogether, these findings demonstrate that integrin α5 mediates the heterotypic cancer cell-fibroblast interaction during peritoneal dissemination of DGC and may thus be a therapeutic target.

Use of anti-spike monoclonal antibodies in kidney transplant recipients with COVID-19: Efficacy, ethnic and racial disparities

Organ transplant recipients may not mount an adequate immune response to COVID‐19 infection and therefore may benefit greatly from passive immunization with anti‐spike monoclonal antibodies (mAbs), which have been shown to decrease hospitalization rates in the general outpatient population. We evaluated the efficacy of mAb therapy in decreasing hospitalizations or emergency room (ER) visits among kidney transplant recipients (KTR) with COVID‐19. We identified KTR with COVID‐19 between March 1, 2020 and April 30, 2021. Patients were excluded if they had multi‐organ transplant or hospital‐acquired COVID‐19. We studied 95 KTR; 20 received mAb. mAb administration was associated with a significant decrease in hospitalizations or ER visits (15% vs. 76%, p < 0.001). This association remained significant after adjustment for potential confounders, and analysis of mAb administration as a time‐dependent variable, with day of symptom onset as day 1 (adjusted HR 0.216, p = 0.04). Black or Hispanic patients were less likely to receive mAb and more likely to be admitted to the hospital or visit the ER. In our KTR population, mAb therapy for COVID‐19 may have helped decrease hospitalizations and ER visits. Healthcare inequities, including access to investigational treatments, have been exacerbated by the COVID‐19 pandemic. Antiviral mAbs are a promising therapeutic modality, especially for immunocompromised patients.

Bamlanivimab and Etesevimab administered in an outpatient setting for SARS-CoV-2 infection

ABSTRACT The early administration of anti-SARS-CoV-2 monoclonal antibodies (mAb) could decrease the risk of severe disease and the need of inpatients care. Herein, our clinical experience with Bamlanivimab/Etesevimab for the treatment of early SARS-CoV-2 infection through an outpatient service was described. Patients with confirmed COVID-19 were selected by General Practitioners (GPs) if eligible to mAb administration, according to manufacturer and AIFA (Agenzia-Italiana-del-Farmaco) criteria. If suitability was confirmed by the Multidisciplinary Team, the patient was evaluated within the next 48–72 hours. Then, all patients underwent a medical evaluation, followed by mAb infusion or hospitalization if the medical condition had worsened. Overall, from March 29th to June 4th, 2021, 106 patients with confirmed COVID-19 were identified by GPs; 26 were considered not eligible and then excluded, while 9 refused treatment. Among the 71 remaining, 6 were not treated because of worsening of symptoms soon after selection. Finally, 65 received mAb therapy. All treated patients survived. However, 2/65 developed adverse events (allergic reaction and atrial fibrillation, respectively) and 6/65 needed hospitalization. By performing univariate logistic regression analysis, diabetes was the only risk factor for hospitalization after mAb administration [aOR = 9.34, 95%CI = 1.31–66.49, p= .026]. Importantly, subjects who worsened awaiting mAb were more frequently obese (OR = 16.66, 95%CI = 1.80–153.9, p= .013) and received home corticosteroid therapy for COVID-19 (OR = 14.11, 95%CI = 1.53–129.6, p= .019). Establishing a network among GPs and COVID units could be an effective strategy to provide mAb treatment to patients with early SARS-CoV-2 infection to reduce hospitalizations and pressure on healthcare systems.

Generation, characterization, and protective ability of mouse monoclonal antibodies against the HA of A (H1N1) influenza virus.

Influenza virus infections pose a continuous threat to human health. Although vaccines function as a preventive and protective tool, they may not be effective due to antigen drift or an inaccurate prediction of epidemic strains. Monoclonal antibodies (mAbs) have attracted wide attention as a promising therapeutic method for influenza virus infections. In this study, three hemagglutinin (HA)-specific mAbs, named 2A1, 2H4, and 2G2, respectively, were derived from mice immunized with the HA protein from A/Michigan/45/2015(H1N1). The isolated mAbs all displayed hemagglutination inhibition activityand the 2G2 mAb exhibited the strongest neutralization effect. Two amino acid mutations (A198E and G173E), recognized in the process of selection of mAb-resistant mutants, were located in antigenic site Sb and Ca1, respectively. In prophylactic experiments, all three mAbs could achieve 100% protection in mice infected with a lethal dose of A/Michigan/45/2015(H1N1). A dose of 1 mg/kg for 2H4 and 2G2 was sufficient to achieve a full protective effect. Therapeutic experiments showed that all three mAbs could protect mice from death if they received the mAb administration at 6 h postinfection, and 2G2 was still protective after 24 h. Our findings indicate that these three mAbs may have potential prevention and treatment value in an H1N1 epidemic, as well as in the study of antigen epitope recognition.

Non-neutralizing antibodies targeting the immunogenic regions of HIV-1 envelope reduce mucosal infection and virus burden in humanized mice.

Antibodies are principal immune components elicited by vaccines to induce protection from microbial pathogens. In the Thai RV144 HIV-1 vaccine trial, vaccine efficacy was 31% and the sole primary correlate of reduced risk was shown to be vigorous antibody response targeting the V1V2 region of HIV-1 envelope. Antibodies against V3 also were inversely correlated with infection risk in subsets of vaccinees. Antibodies recognizing these regions, however, do not exhibit potent neutralizing activity. Therefore, we examined the antiviral potential of poorly neutralizing monoclonal antibodies (mAbs) against immunodominant V1V2 and V3 sites by passive administration of human mAbs to humanized mice engrafted with CD34+ hematopoietic stem cells, followed by mucosal challenge with an HIV-1 infectious molecular clone expressing the envelope of a tier 2 resistant HIV-1 strain. Treatment with anti-V1V2 mAb 2158 or anti-V3 mAb 2219 did not prevent infection, but V3 mAb 2219 displayed a superior potency compared to V1V2 mAb 2158 in reducing virus burden. While these mAbs had no or weak neutralizing activity and elicited undetectable levels of antibody-dependent cellular cytotoxicity (ADCC), V3 mAb 2219 displayed a greater capacity to bind virus- and cell-associated HIV-1 envelope and to mediate antibody-dependent cellular phagocytosis (ADCP) and C1q complement binding as compared to V1V2 mAb 2158. Mutations in the Fc region of 2219 diminished these effector activities in vitro and lessened virus control in humanized mice. These results demonstrate the importance of Fc functions other than ADCC for antibodies without potent neutralizing activity.

Targeting Fc Receptor-Mediated Effects and the "Don't Eat Me" Signal with an Oncolytic Virus Expressing an Anti-CD47 Antibody to Treat Metastatic Ovarian Cancer.

mAbs blocking immune checkpoints have emerged as important cancer therapeutics, as exemplified by systemic administration of the IgG1 anti-CD47 mAb that blocks the "don't eat me" pathway. However, this strategy is associated with severe toxicity. To improve therapeutic efficacy while reducing toxicities for ovarian cancer, we engineered an oncolytic herpesvirus (oHSV) to express a full-length, soluble anti-CD47 mAb with a human IgG1 scaffold (OV-αCD47-G1) or IgG4 scaffold (OV-αCD47-G4). Both IgG1 and IgG4 anti-CD47 mAbs secreted by oHSV-infected tumor cells blocked the CD47-SIRPα signal pathway, enhancing macrophage phagocytosis against ovarian tumor cells. OV-αCD47-G1, but not OV-αCD47-G4, activated human NK-cell cytotoxicity and macrophage phagocytosis by binding to the Fc receptors of these cells. In vivo, these multifaceted functions of OV-αCD47-G1 improved mouse survival in xenograft and immunocompetent mouse models of ovarian cancer when compared with OV-αCD47-G4 and a parental oHSV. The murine counterpart of OV-αCD47-G1, OV-αmCD47-G2b, also enhanced mouse NK-cell cytotoxicity and macrophage phagocytosis and prolonged survival of mice bearing ovarian tumors compared with OV-αmCD47-G3. OV-αmCD47-G2b was also superior to αmCD47-G2b and showed a significantly better effect when combined with an antibody against PD-L1 that was upregulated by oHSV infection. Our data demonstrate that an oHSV encoding a full-length human IgG1 anti-CD47 mAb, when used as a single agent or combined with another agent, is a promising approach for improving ovarian cancer treatment via enhancing innate immunity, as well as performing its known oncolytic function and modulation of immune cells.

Intra-articular delivery of full-length antibodies through the use of an in situ forming depot

Monoclonal antibodies (mAbs) are large size molecules that have demonstrated high therapeutic potential for the treatment of cancer or autoimmune diseases. Despite some excellent results, their intravenous administration results in high plasma concentration. This triggers off-target effects and sometimes poor targeted tissue distribution. To circumvent this issue, we investigated a local controlled-delivery approach using an in situ forming depot technology. Two clinically relevant mAbs, rituximab (RTX) and daratumumab (DARA), were formulated using an injectable technology based on biodegradable PEG-PLA copolymers. The stability and controlled release features of the formulations were investigated. HPLC and mass spectrometry revealed the preservation of the protein structure. In vitro binding of formulated antibodies to their target antigens and to their cellular FcγRIIIa natural killer cell receptor was fully maintained. Furthermore, encapsulated RTX was as efficient as classical intravenous RTX treatment to inhibit the in vivo tumor growth of malignant human B cells in immunodeficient NSG mice. Finally, the intra-articular administration of the formulated mAbs yielded a sustained local release associated with a lower plasma concentration compared to the intra-articular delivery of non-encapsulated mAbs. Our results demonstrate that the utilization of this polymeric technology is a reliable alternative for the local delivery of fully functional clinically relevant mAbs.

39. Anti-Spike Monoclonal Antibody Therapy for Kidney Transplant Recipients with COVID-19

BackgroundOrgan transplant recipients may not mount an adequate immune response to COVID-19 infection, and therefore may benefit greatly from passive immunization with anti-spike monoclonal antibodies (mAb), which have been shown to decrease hospitalization rates in the general outpatient population. We evaluated the efficacy of mAb therapy in decreasing hospitalizations or emergency room (ER) visits among kidney transplant recipients (KTR) with COVID-19.MethodsWe identified KTR with COVID-19 between 3/1/2020 and 4/30/2021. Patients were excluded if they had multiorgan transplant or hospital-acquired COVID-19. Data were analyzed by Cox regression with mAb administration as time-dependent variable, and the day of symptom onset as baseline.ResultsWe studied 95 KTR; 20 received mAb. Comorbidities and immunosuppression were balanced between the two groups. mAb administration was associated with a significant decrease in hospitalizations or ER visits (15 vs. 76%, P< 0.001). This association remained significant after adjustment for confounders and by analyzing mAb administration as a time-dependent variable (Table: adj. HR 0.2, P=0.04). No KTR who received mAb died or required mechanical ventilation. Black or Hispanic KTR were less likely to receive mAb and more likely to be admitted to the hospital or visit the ER (Table).Table Factors significantly associated with hospitalization or ER visit.ConclusionIn our KTR population, mAb therapy for COVID-19 may have helped decrease hospitalizations and ER visits. Healthcare inequities, including access to investigational treatments, were exacerbated by the COVID-19 pandemic. Acknowledging the nonconcurrent control group as a limitation, we found a strong signal for benefit from mAb treatment. Antiviral mAb are a promising therapeutic modality for immunosuppressed patients. Disclosures Dimitrios Farmakiotis, M.D., Astellas (Grant/Research Support)Merck (Grant/Research Support)Viracor (Grant/Research Support)

533. Protocol for and Efficacy of Monoclonal Antibody (mAb) Treatment of SARS-CoV-2 at a VA Medical Center

BackgroundBamlanivimab and casirivimab/imdevimab were the first monoclonal antibodies (mAb) developed against SARS-CoV-2 and proved beneficial early in the course of infection. However, real-world administration of these therapies presents logistical challenges. We present our experience implementing mAb treatment at a large VA Medical Center and review the efficacy of therapy in preventing hospitalization from COVID-19 in a closed healthcare system.MethodsAll positive outpatient COVID tests performed at VA Greater Los Angeles Healthcare System (GLA) were reviewed by the Emergency Medicine (EM) and Infectious Diseases (ID) Sections for mAb eligibility beginning 12/2/2020. Due to limited supply, treatment was prioritized for patients at highest risk of developing severe disease, as determined by EM/ID with input from a machine learning ensemble risk estimation model produced by VA National Artificial Intelligence Institute (Figure 1). If a patient declined or did not reply, treatment was offered to the next patient on a ranked eligibility list. Those who declined or were eligible but not treated were included in the analysis. Patients were excluded if they were hospitalized before treatment was offered. We collected data on age, comorbidities, date of diagnosis, and admission at 30 days after diagnosis. A multivariate log binomial regression was performed to determine the relative risk of admission within 30 days of diagnosis for those who received mAb therapy as compared to those who did not, adjusting for age and comorbidity. All analysis was done in R (version 4.0.5). Results139 patients met inclusion criteria. 45 (32%) received mAb therapy, 48 (35%) declined mAb therapy, and the remaining 46 (33%) either did not respond or were not offered mAb therapy. Hospitalizations following diagnosis in each group are illustrated in Figure 2. There was a trend towards reduced absolute and relative risk of hospitalization (Table 1). There were no anaphylactic events in patients who received mAb therapy. ConclusionAt our facility, a system for rapid identification of candidates and a coordinated distribution plan was essential in ensuring timely administration of mAb therapy to eligible patients. Administration of mAb showed a trend towards decreased risk of hospitalization due to SARS-CoV-2.Disclosures Adela Greeley, MD, Kite (Other Financial or Material Support, My spouse is an employee) Matthew B. Goetz, MD, Nothing to disclose