Antiviral Ranpirnase TMR-001 Inhibits Rabies Virus Release and Cell-to-Cell Infection In Vitro.

Currently, no rabies virus-specific antiviral drugs are available. Ranpirnase has strong antitumor and antiviral properties associated with its ribonuclease activity. TMR-001, a proprietary bulk drug substance solution of ranpirnase, was evaluated against rabies virus in three cell types: mouse neuroblastoma, BSR (baby hamster kidney cells), and bat primary fibroblast cells. When TMR-001 was added to cell monolayers 24 h preinfection, rabies virus release was inhibited for all cell types at three time points postinfection. TMR-001 treatment simultaneous with infection and 24 h postinfection effectively inhibited rabies virus release in the supernatant and cell-to-cell spread with 50% inhibitory concentrations of 0.2-2 nM and 20-600 nM, respectively. TMR-001 was administered at 0.1 mg/kg via intraperitoneal, intramuscular, or intravenous routes to Syrian hamsters beginning 24 h before a lethal rabies virus challenge and continuing once per day for up to 10 days. TMR-001 at this dose, formulation, and route of delivery did not prevent rabies virus transit from the periphery to the central nervous system in this model (n = 32). Further aspects of local controlled delivery of other active formulations or dose concentrations of TMR-001 or ribonuclease analogues should be investigated for this class of drugs as a rabies antiviral therapeutic.

Ranpirnase Reduces HIV-1 Infection and Associated Inflammatory Changes in a Human Colorectal Explant Model.

Ranpirnase (RNP) is a low molecular weight type III endoribonuclease, which demonstrates broad antiviral and antitumor properties. We sought to characterize the antiviral activity of RNP against HIV-1 and to determine whether RNP modulates local inflammatory changes associated with HIV infection in the colorectal explant model. Colorectal explants were incubated for 2 h with HIV-1BaL, in the presence of increasing concentrations of RNP (0-60 µg/mL). After washing, explants were cultured for 14 days, with supernatant collected at days 3, 7, 10, and 14. All samples were assayed for HIV-1 p24. Additionally, 30 soluble inflammatory biomarkers were assayed in the day 3 supernatant sample. Other biopsies were stimulated with lipopolysaccharides (LPS) (10 µg/mL) in the presence of RNP and soluble biomarkers assayed at day 3. RNP inhibited productive infection of the colorectal explants with HIV-1BaL and induced a dose-dependent decrease in 15/30 biomarkers. Affected biomarkers included IP-10, MDC, MIP-1α, MIP-1ß, TARC, IL12-p40, IL-15, IL-17, IL-1α, IL-7, IFNγ, IL12-p70, IL-1ß, IL-4, IL-5, and TNF-ß. Similarly, RNP dose-dependent inhibition was demonstrated in 7/30 biomarkers after LPS stimulation, all of which overlapped with HIV-1BaL-induced biomarker changes. The ability of RNP to inhibit both colorectal explant HIV-1BaL infection and inflammatory changes associated with HIV-1 infection makes RPN a promising agent for topical rectal pre-exposure prophylaxis.

Ranpirnase eradicates human papillomavirus in cultured cells and heals anogenital warts in a Phase I study.

BACKGROUND: Human papillomaviruses (HPV), the causative agents of anogenital warts, are the most prevalent sexually transmitted infectious agents, and wart treatment poses a persistent challenge. We assessed the safety and efficacy of treating HPV with ranpirnase, an endoribonuclease from the northern leopard frog that has been used extensively in Phase III oncology trials. METHODS: As initial verification of ranpirnase antiviral activity, we assessed its ability to eliminate papillomaviruses in cultured cells. To further assess its feasibility for treating anogenital warts in humans, we performed a Phase I study. Forty-two male volunteers with genital/perianal warts were treated topically with three different formulations of 1 mg/ml ranpirnase. Patients were monitored for 8 weeks or until healing. Four patients with HIV were treated in accordance with the compassionate programme but were not evaluated. RESULTS: In cultured cells, ranpirnase showed specific activity against HPV-11 with low toxicity (selectivity index >88). The broad applicability of ranpirnase for treating papillomaviruses was verified using the cottontail rabbit papillomavirus. In the clinical study, eight participants were lost-to-follow-up or discontinued due to protocol violation or non-compliance. Among 30 evaluable participants, topical ranpirnase was moderately well-tolerated, with discontinuation by 5 (16.7%) due to adverse reactions. Clinical healing was achieved by 25 participants (83.3%) and 50% improvement by the 5 discontinued participants (16.7%). The median time to clinical healing was 30 days. CONCLUSIONS: This study provides the first in vitro and clinical evidence of the antiviral efficacy of ranpirnase against HPV and supports assessment of ranpirnase in expanded clinical studies.

Antiviral effect of ranpirnase against Ebola virus.

The recent epidemic of Ebola has intensified the need for the development of novel antiviral therapeutics that prolong and improve survival against deadly viral diseases. We sought to determine whether ranpirnase, an endoribonuclease from Rana pipiens with a demonstrated human safety profile in phase III oncology trials, can reduce titers of Ebola virus (EBOV) in infected cells, protect mice against mouse-adapted EBOV challenge, and reduce virus levels in infected mice. Our results demonstrate that 0.50 µg/ml ranpirnase is potently effective at reducing EBOV Zaire Kikwit infection in cultured Vero E6 cells (Selectivity Index 47.8-70.2). In a prophylactic study, a single intravenous dose of 0.1 mg/kg ranpirnase protected 70% of mice from progressive infection. Additionally, in a post-exposure prophylactic study, 100% of female mice survived infection after intraperitoneal administration of 0.1 mg/kg ranpirnase for ten days beginning 1 h post challenge. Most of the male counterparts were sacrificed due to weight loss by Study Day 8 or 9; however, the Clinical Activity/Behavior scores of these mice remained low and no significant microscopic pathologies could be detected in the kidneys, livers or spleens. Furthermore, live virus could not be detected in the sera of ranpirnase-treated mice by Study Day 8 or in the kidneys, livers or spleens by Study Day 12, and viral RNA levels declined exponentially by Study Day 12. Because ranpirnase is exceptionally stable and has a long track record of safe intravenous administration to humans, this drug provides a promising new candidate for clinical consideration in the treatment of Ebola virus disease alone or in combination with other therapeutics.