Isolation and characterization of a dideoxyguanosine triphosphate-resistant mutant of human immunodeficiency virus reverse transcriptase

The appearance of drug-resistant strains of viral pathogens is a major difficulty confounding current efforts to block viral infections. The identification and analysis of mutations responsible for drug resistance can provide important clues helpful in understanding the mechanisms of resistance and in the eventual development of better therapies. We have used a direct screening method to scan libraries of mutagenized genes encoding the reverse transcriptase of human immunodeficiency virus type 1, and have recovered a variant enzyme that is resistant to the chain-terminator inhibitor 2',3'-dideoxyguanosine triphosphate. The single substitution mutation in this variant conferred broad crossresistance to a variety of other antiviral compounds currently in clinical trials. Virus carrying the mutation was fully infectious in cultured human lymphocytes. The replication of the mutant virus was highly resistant to phosphonoformic acid but did not show increased resistance to the prodrug dideoxyguanosine

Human immunodeficiency virus type 1 mutants resistant to nonnucleoside inhibitors of reverse transcriptase arise in tissue culture

We have recently described a nonnucleoside compound that specifically inhibits the reverse transcriptase of human immunodeficiency virus type 1 (HIV-1), the causative agent of AIDS. This compound, nevirapine (BI-RG-587), interacts with highly conserved tyrosine residues at positions 181 and 188 in the reverse transcriptase to inhibit the recombinant enzyme and virus replication in cell culture with 50% inhibitory concentrations in the 40 nM range. HIV-1 variants resistant to nevirapine emerged with passage in cell culture in the presence of drug. This resistant phenotype was stable with continued passage in the absence of drug. These mutants had a substitution of cysteine for the tyrosine at position 181. Introduction of this mutation into the recombinant enzyme increased the inhibitory concentration of nevirapine 100-fold. Substitution of cysteine for tyrosine at residue 181 into the wild-type viral genome conferred a similar reduction in susceptibility to nevirapine. Mutants were also resistant to a tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione derivative and two 6-phenylthiouracil derivatives but retained their sensitivity to the other reverse transcriptase inhibitors, 3'-azido-3'-deoxythymidine and foscarnet

Human monoclonal antibodies directed against toxins A and B prevent Clostridium difficile-induced mortality in hamsters

Clostridium difficile is the leading cause of nosocomial antibiotic-associated diarrhea, and recent outbreaks of strains with increased virulence underscore the importance of identifying novel approaches to treat and prevent relapse of Clostridium difficile-associated diarrhea (CDAD). CDAD pathology is induced by two exotoxins, toxin A and toxin B, which have been shown to be cytotoxic and, in the case of toxin A, enterotoxic. In this report we describe fully human monoclonal antibodies (HuMAbs) that neutralize these toxins and prevent disease in hamsters. Transgenic mice carrying human immunoglobulin genes were used to isolate HuMAbs that neutralize the cytotoxic effects of either toxin A or toxin B in cell-based in vitro neutralization assays. Three anti-toxin A HuMAbs (3H2, CDA1, and 1B11) could all inhibit the enterotoxicity of toxin A in mouse intestinal loops and the in vivo toxicity in a systemic mouse model. Four anti-toxin B HuMAbs (MDX-1388, 103-174, 1G10, and 2A11) could neutralize cytotoxicity in vitro, although systemic toxicity in the mouse could not be neutralized. Anti-toxin A HuMAb CDA1 and anti-toxin B HuMAb MDX-1388 were tested in the well-established hamster model of C. difficile disease. CDA1 alone resulted in a statistically significant reduction of mortality in hamsters; however, the combination treatment offered enhanced protection. Compared to controls, combination therapy reduced mortality from 100% to 45% (P\u3c0.0001) in the primary disease hamster model and from 78% to 32% (P\u3c0.0001) in the less stringent relapse model

PD-1 blockade in recurrent or metastatic cervical cancer: Data from cemiplimab phase I expansion cohorts and characterization of PD-L1 expression in cervical cancer

Objectives: To characterize the safety, tolerability, and anti-tumor activity of cemiplimab as monotherapy or in combination with hypofractionated radiation therapy (hfRT) in patients with recurrent or metastatic cervical cancer. To determine the association between histology and programmed death-ligand 1 (PD-L1) expression. Methods: In non-randomized phase I expansion cohorts, patients (squamous or non-squamous histology) received cemiplimab 3 mg/kg intravenously every 2 weeks for 48 weeks, either alone (monotherapy cohort) or with hfRT during week 2 (combination cohort). Due to insufficient tissue material, PD-L1 protein expression was evaluated in commercially purchased samples and mRNA expression levels were analyzed from The Cancer Genome Atlas (TCGA). Results: Twenty patients enrolled in both cohorts in total; 10 had squamous histology. The most common adverse events of any grade were diarrhea, fatigue, and hypokalemia, occurring in 35%, 25%, and 25%, respectively. Objective response rate was 10% in each cohort; responders had squamous histology. Duration of response was 11.2 months and 6.4 months for the responder in the monotherapy and combination cohort, respectively. Irradiated lesions were not included in the response assessments. In separate archived specimens (N = 155), PD-L1 protein expression in tumor and immune cells was negative (<1%) more commonly in adenocarcinoma than in squamous tumors. PD-L1 mRNA levels were lower in adenocarcinoma than squamous cell tumors (1.2 vs 5.0 mean transcripts per million, respectively) in TCGA. Conclusions: Cemiplimab has activity in cervical squamous cell carcinoma. The phase I results, combined with results from other anti-PD-1 trials in cervical cancer and our biomarker analyses have informed the design of the ongoing phase III trial, with the primary overall survival hierarchical analyses being done first in patients with squamous histology

Interim Analysis of Phase 2 Results for Cemiplimab in Patients with Metastatic Basal Cell Carcinoma (mBCC) who Progressed on or are Intolerant to Hedgehog Inhibitors (HHIs)

Abstract not available

Primary Analysis of Phase 2 Results for Cemiplimab in Patients (pts) with Locally Advanced Basal Cell Carcinoma (laBCC) who Progress on or are Intolerant to Hedgehog Inhibitors (HHIs)

Abstract not available

PD-1 blockade with cemiplimab in advanced cutaneous squamous-cell carcinoma

BACKGROUNDNo systemic therapies have been approved for the treatment of advanced cutaneous squamous-cell carcinoma. This cancer may be responsive to immune therapy, because the mutation burden of the tumor is high and the disease risk is strongly associated with immunosuppression. In the dose-escalation portion of the phase 1 study of cemiplimab, a deep and durable response was observed in a patient with metastatic cutaneous squamous-cell carcinoma.METHODSWe report the results of the phase 1 study of cemiplimab for expansion cohorts of patients with locally advanced or metastatic cutaneous squamous-cell carcinoma, as well as the results of the pivotal phase 2 study for a cohort of patients with metastatic disease (metastatic-disease cohort). In both studies, the patients received an intravenous dose of cemiplimab (3 mg per kilogram of body weight) every 2 weeks and were assessed for a response every 8 weeks. In the phase 2 study, the primary end point was the response rate, as assessed by independent central review.RESULTSIn the expansion cohorts of the phase 1 study, a response to cemiplimab was observed in 13 of 26 patients (50%; 95% confidence interval [CI], 30 to 70). In the metastatic-disease cohort of the phase 2 study, a response was observed in 28 of 59 patients (47%; 95% CI, 34 to 61). The median follow-up was 7.9 months in the metastatic-disease cohort of the phase 2 study. Among the 28 patients who had a response, the duration of response exceeded 6 months in 57%, and 82% continued to have a response and to receive cemiplimab at the time of data cutoff. Adverse events that occurred in at least 15% of the patients in the metastatic-disease cohort of the phase 2 study were diarrhea, fatigue, nausea, constipation, and rash; 7% of the patients discontinued treatment because of an adverse event.CONCLUSIONSAmong patients with advanced cutaneous squamous-cell carcinoma, cemiplimab induced a response in approximately half the patients and was associated with adverse events that usually occur with immune checkpoint inhibitors

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research