Jeff Cehelsky

RATIONALE: Respiratory syncytial virus (RSV) is the leading cause of childhood lower respiratory infection, yet viable therapies are lacking. Two major challenges have stalled antiviral development: ethical difficulties in performing pediatric proof-of-concept studies and the prevailing concept that the disease is immune-mediated rather than being driven by viral load. OBJECTIVES: The development of a human experimental wild-type RSV infection model to address these challenges. METHODS: Healthy volunteers (n = 35), in five cohorts, received increasing quantities (3.0-5.4 log plaque-forming units/person) of wild-type RSV-A intranasally. MEASUREMENTS AND MAIN RESULTS: Overall, 77% of volunteers consistently shed virus. Infection rate, viral loads, disease severity, and safety were similar between cohorts and were unrelated to quantity of RSV received. Symptoms began near the time of initial viral detection, peaked in severity near when viral load peaked, and subsided as viral loads (measured by real-time polymerase chain reaction) slowly declined. Viral loads correlated significantly with intranasal proinflammatory cytokine concentrations (IL-6 and IL-8). Increased viral load correlated consistently with increases in multiple different disease measurements (symptoms, physical examination, and amount of nasal mucus). CONCLUSIONS: Viral load appears to drive disease manifestations in humans with RSV infection. The observed parallel viral and disease kinetics support a potential clinical benefit of RSV antivirals. This reproducible model facilitates the development of future RSV therapeutics.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in children and is responsible for as many as 199,000 childhood deaths annually worldwide. To support the development of viral therapeutics and vaccines for RSV, a human adult experimental infection model has been established. In this report, we describe the provenance and sequence of RSV Memphis-37, the low-passage clinical isolate used for the model's reproducible, safe, experimental infections of healthy, adult volunteers. The predicted amino acid sequences for major proteins of Memphis-37 are compared to nine other RSV A and B amino acid sequences to examine sites of vaccine, therapeutic, and pathophysiologic interest. Human T- cell epitope sequences previously defined by in vitro studies were observed to be closely matched between Memphis-37 and the laboratory strain RSV A2. Memphis-37 sequences provide baseline data with which to assess: (i) virus heterogeneity that may be evident following virus infection/transmission, (ii) the efficacy of candidate RSV vaccines and therapeutics in the experimental infection model, and (iii) the potential emergence of escape mutants as a consequence of experimental drug treatments. Memphis-37 is a valuable tool for pre-clinical research, and to expedite the clinical development of vaccines, therapeutic immunomodulatory agents, and other antiviral drug strategies for the protection of vulnerable populations against RSV disease.

3025 Background: ALN-VSP02 is a RNA interference (RNAi) therapeutic comprised of lipid nanoparticle-formulated small interfering RNAs (siRNAs) targeting the expression of vascular endothelial growth factor (VEGF)-A and kinesin spindle protein (KSP). Methods: A multi-center, open label, phase I dose-escalation trial of ALN-VSP02 administered as a 15-minute iv infusion q2 wks was initiated in patients (pts) with advanced solid tumors and at least one measurable liver lesion. Main objectives included evaluation of safety/tolerability and assessment of PK/PD. Results: Thirty-one pts were enrolled across 7 dose levels (0.1-1.5 mg/kg); median age 57 yrs, all with multiple prior therapies. A total of 140 doses were administered, mean of 4.5 (range 1-17). Treatment was generally well-tolerated, with no dose-dependent trends in clinical or laboratory adverse events. One on-study death (liver failure in a pt with near complete replacement of the liver by tumor) deemed possibly related to treatment occurred at 0.7 mg/kg. Low-grade acute infusion reactions occurred in 10% of pts and were managed with slowing of infusion. Dose-limiting toxicities at doses >0.7 mg/kg included 1 episode each of reversible grade 3 thrombocytopenia (1.25 mg/kg) and hypokalemia (1.5 mg/kg). Plasma PK showed dose-proportional AUC and Cmax. Post-treatment biopsies from 10 pts (7 liver and 3 extrahepatic tumors) showed pharmacologically relevant concentrations (0.3-142 ng/g tissue) of both siRNAs. Molecular evidence of RNAi-mediated VEGF mRNA cleavage was shown in liver (n=2 at 0.4 mg/kg) and in an extrahepatic tumor (ovarian cancer at 1.25 mg/kg) through use of the 5’ RACE assay on tumor biopsies. Additional evidence for an anti-VEGF effect with ALN-VSP02 included a decrease in Ktrans of at least 40% by DCE-MRI in 56% of evaluable pts. Among 27 pts evaluable for response, 8.3% (1 of 12) at doses ≤ 0.4 mg/kg had stable disease (SD) for at least 2 mo compared to 46.6% (7/15) with SD (n=6) or PR (n=1, endometrial cancer with liver metastases) at doses ≥ 0.7 mg/kg. Conclusions: ALN-VSP02 is well-tolerated and has antitumor activity. Pharmacodynamic data are consistent with an anti-VEGF effect, and 1.25 mg/kg q2wks is the recommended phase II dose.