Data collected from 182 marketed and nonmarketed pharmaceuticals demonstrate that there is little value gained in conducting a rat two-year carcinogenicity study for compounds that lack: (1) histopathologic risk factors for rat neoplasia in chronic toxicology studies, (2) evidence of hormonal perturbation, and (3) positive genetic toxicology results. Using a single positive result among these three criteria as a test for outcome in the two-year study, fifty-two of sixty-six rat tumorigens were correctly identified, yielding 79% test sensitivity. When all three criteria were negative, sixty-two of seventy-six pharmaceuticals (82%) were correctly predicted to be rat noncarcinogens. The fourteen rat false negatives had two-year study findings of questionable human relevance. Applying these criteria to eighty-six additional chemicals identified by the International Agency for Research on Cancer as likely human carcinogens and to drugs withdrawn from the market for carcinogenicity concerns confirmed their sensitivity for predicting rat carcinogenicity outcome. These analyses support a proposal to refine regulatory criteria for conducting a two-year rat study to be based on assessment of histopathologic findings from a rat six-month study, evidence of hormonal perturbation, genetic toxicology results, and the findings of a six-month transgenic mouse carcinogenicity study. This proposed decision paradigm has the potential to eliminate over 40% of rat two-year testing on new pharmaceuticals without compromise to patient safety.

BaCKgRoUND aND aIMS:Survival data among patients with hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC) after achieving sustained virologic response (SVR) with interferon-free direct-acting antivirals (DAAs) in both Asian and western countries are limited. Survival rates were compared between patients with HCV-related HCC who were untreated for HCV and those who achieved SVR. appRoaCH aND ReSUltS: Using data from two U.S. and six Asian centers from 2005 to 2017, we categorized 1,676 patients who were mono-infected with HCV-related HCC into patients untreated for HCV (untreated group) and DAA-treated patients with SVR (SVR group) and matched by propensity score matching (PSM); multivariable Cox regression with HCV treatment status as a time-varying covariate was used to determine mortality risk and landmark analysis to avoid immortal time bias. There were 1,239 untreated patients and 437 patients with SVR. After PSM, background risks of the 321 pairs of matched patients were balanced (all P > 0.05). After time-varying adjustment for HCV treatment initiation compared with untreated patients, patients with SVR had significantly higher 5-year overall survival (87.78% vs. 66.05%, P < 0.001). Multivariable Cox regression showed that SVR was independently associated with a 63% lower risk of 5-year all-cause mortality (hazard ratio [HR], 0.37; 95% confidence interval [CI], 0.16-0.83; P = 0.016) and 66% lower risk of 5-year liver-related mortality (HR, 0.34; 95% CI, 0.13-0.88; P = 0.026) with similar trends after removing patients with liver transplants. Landmark analysis at 90, 180, and 360 days showed consistent results (HRs ranged 0.22 to 0.44, all P < 0.05). CoNClUSIoN:In this multinational consortium, patients with HCV-related HCC who obtained SVR achieved a 60%-70% improvement in 5-year survival (both all-cause and liver related) compared with patients untreated for HCV. Patients eligible for HCC therapy should also be considered for DAA therapy.

The Programmed Death-1 (PD-1) receptor delivers inhibitory checkpoint signals to activated T cells upon binding to its ligands PD-L1 and PD-L2 expressed on antigen-presenting cells and cancer cells, resulting in suppression of T-cell effector function and tumor immune evasion. Clinical antibodies blocking the interaction between PD-1 and PD-L1 restore the cytotoxic function of tumor antigen-specific T cells, yielding durable objective responses in multiple cancers. This report describes the preclinical characterization of REGN2810, a fully human hinge-stabilized IgG4 (S228P) high-affinity anti-PD-1 antibody that potently blocks PD-1 interactions with PD-L1 and PD-L2. REGN2810 was characterized in a series of binding, blocking, and functional cell-based assays, and preclinical in vivo studies in mice and monkeys. In cellbased assays, REGN2810 reverses PD-1-dependent attenuation of T-cell receptor signaling in engineered T cells and enhances responses of human primary T cells. To test the in vivo activity of REGN2810, which does not cross-react with murine PD-1, knockin mice were generated to express a hybrid protein containing the extracellular domain of human PD-1, and transmembrane and intracellular domains of mouse PD-1. In these mice, REGN2810 binds the humanized PD-1 receptor and inhibits growth of MC38 murine tumors. As REGN2810 binds to cynomolgus monkey PD-1 with high affinity, pharmacokinetic and toxicologic assessment of REGN2810 was performed in cynomolgus monkeys. High doses of REGN2810 were well tolerated, without adverse immune-related effects. These preclinical studies validate REGN2810 as a potent and promising candidate for cancer immunotherapy.

In the tumor microenvironment, multiple inhibitory checkpoint receptors can suppress T-cell function, thereby enabling tumor immune evasion. Blockade of one of these checkpoint receptors, PD-1, with therapeutic antibodies has produced positive clinical responses in various cancers; however, the efficacy of this approach can be further improved. Simultaneously targeting multiple inhibitory checkpoint receptors has emerged as a promising therapeutic strategy. Here, we report the development and characterization of REGN3767, a fully human IgG4 antibody targeting LAG-3, another inhibitory receptor on T cells. REGN3767 binds human and monkey LAG-3 with high affinity and specificity and blocks the interaction of LAG-3 with its ligand, MHC class II. In an engineered T-cell/antigenpresenting cell bioassay, REGN3767 alone, or in combina-tion with cemiplimab (REGN2810, human anti-PD-1 antibody), blocked inhibitory signaling to T cells mediated by hLAG-3/MHCII in the presence of PD-1/PD-L1. To test the in vivo activity of REGN3767 alone or in combination with cemiplimab, we generated human PD-1xLAG-3 knockin mice, in which the extracellular domains of mouse Pdcd1 and Lag3 were replaced with their human counterparts. In these humanized mice, treatment with cemiplimab and REGN3767 showed increased efficacy in a mouse tumor model and enhanced the secretion of proinflammatory cytokines by tumor-specific T cells. The favorable pharmacokinetics and toxicology of REGN3767 in nonhuman primates, together with enhancement of antitumor efficacy of anti-PD-1 antibody in preclinical tumor models, support its clinical development.

We have evaluated the DNA vaccination strategy for measles virus (MV) hemagglutinin (HA) and nucleoprotein (NP) genes. Plasmids encoding either the MV, HA, or NP proteins inoculated intramuscularly into Balb/c mice induced both humoral and CTL class I restricted responses. Antibody responses were not increased by multiple inoculations. The major antibody isotype induced by both the HA and NP was IgG2a consistent with a Th1 response. In contrast, immunization with a plasmid which directed the synthesis of a partially secreted form of HA gave mainly IgG1 antibodies. When the amount of DNA was reduced for the HA plasmid (1 or 10 microg/animal), although the antibody was not induced, a CTL response was observed.

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COVID-19 (Coronavirus Disease 2019), the disease caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2) is an ongoing global public health emergency. As understanding of the health effects of COVID-19 has improved, companies and agencies worldwide have worked together to identify therapeutic approaches, fast-track clinical trials and pathways for emergency use, and approve therapies for patients. This work has resulted in therapies that not only improve survival, reduce time of hospitalization, and time to recovery, but also include preventative measures, such as vaccines. This manuscript discusses development programs for 3 products that are approved or authorized for emergency use at the time of writing: VEKLURY (remdesivir, direct-acting antiviral from Gilead Sciences, Inc.), REGEN-COV (casirivimab and imdevimab antibody cocktail from Regeneron Pharmaceuticals Inc.), and Comirnaty (Pfizer-BioNTech COVID-19 Vaccine [Pfizer, Inc.-BioNTech]), and perspectives from the U.S. Food and Drug Administration.