Olgotrelvir, a dual inhibitor of SARS-CoV-2 Mpro and cathepsin L, as a standalone antiviral oral intervention candidate for COVID-19

BACKGROUND

Oral antiviral drugs with improved antiviral potency and safety are needed to address current challenges in clinical practice for treatment of COVID-19, including the risks of rebound, drug-drug interactions, and emerging resistance.

METHODS

Olgotrelvir (STI-1558) is designed as a next-generation antiviral targeting the SARS-CoV-2 main protease (Mpro), an essential enzyme for SARS-CoV-2 replication, and human cathepsin L (CTSL), a key enzyme for SARS-CoV-2 entry into host cells.

FINDINGS

Olgotrelvir is a highly bioavailable oral prodrug that is converted in plasma to its active form, AC1115. The dual mechanism of action of olgotrelvir and AC1115 was confirmed by enzyme activity inhibition assays and co-crystal structures of AC1115 with SARS-CoV-2 Mpro and human CTSL. AC1115 displayed antiviral activity by inhibiting replication of all tested SARS-CoV-2 variants in cell culture systems. Olgotrelvir also inhibited viral entry into cells using SARS-CoV-2 Spike-mediated pseudotypes by inhibition of host CTSL. In the K18-hACE2 transgenic mouse model of SARS-CoV-2-mediated disease, olgotrelvir significantly reduced the virus load in the lungs, prevented body weight loss, and reduced cytokine release and lung pathologies. Olgotrelvir demonstrated potent activity against the nirmatrelvir-resistant Mpro E166 mutants. Olgotrelvir showed enhanced oral bioavailability in animal models and in humans with significant plasma exposure without ritonavir. In phase I studies (ClinicalTrials.gov: NCT05364840 and NCT05523739), olgotrelvir demonstrated a favorable safety profile and antiviral activity.

CONCLUSIONS

Olgotrelvir is an oral inhibitor targeting Mpro and CTSL with high antiviral activity and plasma exposure and is a standalone treatment candidate for COVID-19.

FUNDING

Funded by Sorrento Therapeutics.

Abstract CT189: PRTX007, an optimized TLR7 agonist for systemic immunotherapy of cancers: Interim analysis of phase I study in healthy volunteers

Background. Toll-like receptor 7 (TLR7) agonists have long been recognized as potential systemic anti-cancer immunotherapy agents. However, clinical development has been limited by complex target-mediated pharmacology including those associated with elevated levels of proinflammatory factors, which also limit the ability to combine with immune checkpoint inhibitors (CPI). PRTX007 is an orally administered prodrug of PRX034, a novel TLR7 agonist that elicits IFN-mediated immune induction without inducing inflammation via the NF-κβ pathway. QOD dosing in primates maintains a stable immune response without immune exhaustion or toxicity. Efficacy, safety, and compatibility with immune CPI were demonstrated in a CT26 syngeneic rodent tumor model.

Methods. We conducted a phase 1, single-center, prospective, randomized, double-blind placebo-controlled study of 8 single-ascending dose (SAD) and 4 multiple-ascending dose (MAD) cohorts of PRTX007 administered orally to healthy adult participants. Primary objectives were safety and tolerability. Secondary objectives were evaluation of pharmacokinetics (PK) and pharmacodynamics. This interim analysis focuses on the 8 SAD (50-600 mg) and 2 MAD (300-400 mg) cohorts, with 64 of the 84 participants in the study receiving drug.

Results. Treatment-related adverse events include non-dose‒related mild headache, and minor dose-related increases in ALT (<2X ULN) that rapidly resolved. The PKs of PRTX007 and PRX034 are well-behaved eg, exposure increasing proportionally with PRTX007 dose. Consistent with studies in human cells in vitro and non-human primates in vivo, oral administration of PRTX007 elicits systemic TLR7-mediated immune induction without engaging NF-κβ─mediated biosynthesis of IL-6, TNFα and IL-1β in humans. A single dose of PRTX007 (300-600 mg) elicits coordinated expression of IFN-stimulated genes (ISGs) in blood without quantifiable increases in circulating IFNs. At 500 and 600 mg doses, IP-10, IL-1RA, MCP-1 and TRAIL but not IL-6, TNFα or IL-1β increase in plasma (maximal response = 4020, 1460, 650 and 360 pg/ml, respectively). When PRTX007 is administered for 2 weeks on a QOD schedule at 400 mg/dose, the degree of ISG expression progressively increases when compared to the first-dose response, (eg, ISG15 increases 2.1-fold [geometric mean] following Dose 1 vs pretreatment baseline, rising to 12.2-fold following Dose 7). This is accompanied by modest activation of circulating NK, B, and CD4+ and CD8+ T cells as measured by cell-surface markers. IL-6, TNFα and IL-1β remain unchanged from pretreatment levels.

Conclusion. At the interim analysis, PRTX007 demonstrated a favorable safety profile when administered orally to all tested SAD and MAD cohorts. Dose-dependent systemic exposure was observed, as well as activation of the innate immune response, without production of proinflammatory factors.

Citation Format: Charlotte Lemech, Christopher Argent, Curtis Scribner, Richard Daniels, James Richard Appleman. PRTX007, an optimized TLR7 agonist for systemic immunotherapy of cancers: Interim analysis of phase I study in healthy volunteers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT189.

Maternal responses to daily maternal porcine somatotropin injections during early-mid pregnancy or early-late pregnancy in sows and gilts

Piglet neonatal survival and postnatal growth and efficiency are positively related to birth weight. In gilts, daily maternal porcine ST (pST) injections from d 25 to 100 (term approximately 115 d), but not d 25 to 50, of pregnancy increase progeny birth weight. Daily maternal pST injections from d 25 to 50 increase fetal weight at d 50 in gilts and sows. We therefore hypothesized that daily pST injections from d 25 to 100, but not d 25 to 50, of pregnancy would increase birth weight similarly in both parities. Landrace x Large White gilts and sows were uninjected (controls) or were injected daily with pST (gilts: 2.5 mg/d; sows: 4.0 mg/d, each approximately 15 microg of pST/kg per day) from d 25 to 50 or 100 of pregnancy. Litter size and BW were recorded at birth, midlactation, and weaning. Dams were followed through the subsequent mating and pregnancy. Maternal pST injections from d 25 to 100, but not d 25 to 50, increased mean piglet birth weight by 11.6% in sows (P <or= 0.001) and by 5.6% in gilts (P = 0.008). Both pST treatments decreased litter size by approximately 0.6 live-born piglets (each P <or= 0.025). In sows, maternal pST treatment from d 25 to 100 increased culls at weaning (P = 0.037). In remated dams, prior treatments did not affect (P > 0.1) the weaning-remating interval, conception rate, or subsequent litter size. Greater pST-induced birth weight increases in sows than in gilts may mean that underlying metabolic or placental mechanisms for pST action are constrained by maternal competition for nutrients in rapidly growing gilts.