Safety, Tolerability, and Pharmacokinetics of an Oral Small Molecule Inhibitor of IL-17A (LY3509754): A Phase I Randomized Placebo-Controlled Study

For some patients with psoriasis, orally administered small molecule inhibitors of interleukin (IL)-17A may represent a convenient alternative to IL-17A-targeting monoclonal antibodies. This first-in-human study assessed the safety, tolerability, pharmacokinetics (PKs), and peripherally circulating IL-17A target engagement profile of single or multiple oral doses of the small molecule IL-17A inhibitor LY3509754 (NCT04586920). Healthy participants were randomly assigned to receive LY3509754 or placebo in sequential escalating single ascending dose (SAD; dose range 10-2,000 mg) or multiple ascending dose (MAD; dose range 100-1,000 mg daily for 14 days) cohorts. The study enrolled 91 participants (SAD, N = 51 and MAD, N = 40) aged 21-65 years (71% men). LY3509754 had a time to maximum concentration (Tmax) of 1.5-3.5 hours, terminal half-life of 11.4-19.1 hours, and exhibited dose-dependent increases in exposure. LY3509754 had strong target engagement, indicated by elevated plasma IL-17A levels within 12 hours of dosing. Four participants from the 400-mg (n = 1) and 1,000-mg (n = 3) MAD cohorts experienced increased liver transaminases or acute hepatitis (onset ≥ 12 days post-last LY3509754 dose), consistent with drug-induced liver injury (DILI). One case of acute hepatitis was severe, resulted in temporary hospitalization, and was classified as a serious adverse event. No adverse effects on other major organ systems were observed. Liver biopsies from three of the four participants revealed lymphocyte-rich, moderate-to-severe lobular inflammation. We theorize that the DILI relates to an off-target effect rather than IL-17A inhibition. In conclusion, despite strong target engagement and a PK profile that supported once-daily administration, this study showed that oral dosing with LY3509754 was poorly tolerated.

Abstract 5225: Temporal inhibition of ERK is sufficient for tumor growth inhibition in KRAS-mutant or BRAF-mutant tumors

The combination of BRAF and MEK inhibitors have been clinically studied, and three different combinations (dabrafenib plus trametinib, vemurafenib plus cobimetinib and encorafenib plus binimetinib) are approved by the FDA for treatment of melanoma patients with BRAF V600E mutation. Published reports indicate that each combination has a different efficacy and toxicity profile. It is believed that the toxicity profile of some of these drugs is linked to their pharmacokinetic (PK) profile leading to prolonged pharmacodynamics (PD) or target inhibition. ERK inhibitors have been discovered recently to overcome the acquired resistance to BRAF plus MEK inhibitors in BRAF-mutant melanoma and for combination therapies in RAS/MAPK altered cancers including KRAS-mutant cancers. Several ERK inhibitors have entered clinical development as monotherapy or in combination. However, it is not clear what the minimum time on target is required for efficacy without causing significant toxicity, and whether that would differentiate the therapeutic index of one inhibitor from another. Therefore, we have conducted PK-PD-efficacy relationship studies of different MEK and ERK inhibitors with different PK profiles in mice in BRAF-mutant or KRAS-mutant xenograft models to determine the minimum time on target required for efficacy. We have tested the PK-PD-efficacy of MEK inhibitors trametinib and cobimetinib, as well as ERK inhibitors BVD-523, GDC-0994 and LY3214996 in BRAF V600E or KRAS mutant xenograft models including A375 BRAF V600E melanoma, Colo205 BRAF V600E colorectal carcinoma and HCT116 KRAS G13D colorectal carcinoma. Additionally, an infusion study with LY3214996 was conducted in rats implanted with HCT116 colorectal carcinoma tumors, where drug exposure was controlled for a specified time to get ≥50% pRSK1 inhibition. Our data suggests that ≥50% inhibition of pRSK1 for 8h is required for significant efficacy of ERK inhibitor LY3214996, which is similar to the data presented for GDC-0994 (Robarge K et al, Abstract number DDT02-03, AACR Annual Meeting 2014). Overall assessment of the data in different models suggested that ≥50% target inhibition for 8-16h is enough for significant tumor growth inhibition and regressions by an ERK inhibitor in BRAF-mutant or KRAS-mutant tumors without any obvious toxicity as measured by body weight loss or mortality. LY3214996 is in Phase 1 clinical development and the preliminary PK profile in patients looks as predicted from preclinical data. Therefore, we believe that the PK profile of LY3214996 offers flexibility with dose and schedule to balance efficacy and safety, and to achieve a better therapeutic index in combination therapy for RAS/MAPK pathway altered cancers.

Citation Format: Shripad V. Bhagwat, Weihua Shen, Baohui Zhao, Shufen Cai, Lisa Kindler, William T. McMillen, Eunice Yuen, Denis McCann, Jason Manro, Andrew J. Dropsey, Melinda D. Willard, Sajan Joseph, Sheng-Bin Peng. Temporal inhibition of ERK is sufficient for tumor growth inhibition in KRAS-mutant or BRAF-mutant tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5225.