TLN-372

Kestrel Therapeutics, a Massachusetts-based biotechnology company, has opened a first-in-human Phase I clinical trial for KST-6051, an oral small-molecule inhibitor designed to block mutant KRAS across multiple oncogenic alleles. The study targets adults with advanced or metastatic KRAS-mutant solid tumors — primarily non-small cell lung cancer (NSCLC), pancreatic ductal adenocarcinoma (PDAC), and colorectal cancer (CRC) — and positions KST-6051 as a potential pan-KRAS agent at a moment when the field is moving beyond the allele-specific inhibitors that defined the first generation of direct KRAS-targeted therapy. The open-label, multicenter, sequential dose-escalation study (NCT07458347) plans to enroll up to 145 participants across four US sites, including Moffitt Cancer Center in Tampa and NEXT Oncology in San Antonio. Primary completion is expected in Q2 2027, with full study completion projected for Q2 2028. Primary endpoints center on safety and tolerability — specifically the incidence of treatment-related adverse events, treatment-emergent adverse events, and dose-limiting toxicities during the first 21-day cycle. Secondary endpoints include objective response rate, progression-free survival, disease control rate, duration of response, and pharmacokinetic parameters measured through week six. One key eligibility criterion distinguishes this population from trials of approved KRAS inhibitors: participants must not have received prior RAS or KRAS inhibitor therapy, potentially positioning KST-6051 as a first-line molecularly targeted option rather than a salvage strategy. KRAS mutations drive oncogenic signaling in roughly 25% of all human cancers, with the highest prevalence in PDAC (approximately 90%), CRC (approximately 40%–45%), and NSCLC (approximately 25%–30%). For decades, KRAS was considered pharmacologically intractable because its GTP-binding site offered no obvious drug-binding pocket and because the protein cycles rapidly between active and inactive states. The identification of the Switch-II pocket (SIIP) — a cryptic allosteric site that becomes accessible during conformational transitions — changed that calculus. Sotorasib and adagrasib, both FDA-approved for KRAS G12C-mutant NSCLC, exploit this pocket through covalent chemistry that traps the GDP-bound, inactive form of the protein. That approach is inherently allele-specific: the covalent warhead requires the unique cysteine introduced by the G12C substitution, and it is inactive against the GTP-loaded, signaling-competent state of KRAS. KST-6051 appears to have been designed to address both constraints. According to available source material, the compound binds the Switch-II pocket through non-covalent interactions and retains activity against KRAS in both its GDP-bound (OFF) and GTP-bound (ON) conformational states. That dual-state activity, if confirmed in humans, would represent a mechanistic departure from the approved agents: rather than trapping a single inactive conformation, KST-6051 would need to compete with intracellular GTP concentrations to suppress the active form — a pharmacological challenge that has driven much of the chemistry innovation in the pan-KRAS field. The trial’s condition keywords explicitly include “Pan KRAS,” and the eligibility criteria require only a documented KRAS mutation of any type, confirming the mutation-agnostic enrollment strategy. KST-6051 originates from a preclinical RAS program acquired from Anchiano Therapeutics, which Kestrel subsequently advanced through IND-enabling development. The pan-KRAS space has attracted several other entrants. Eli Lilly’s LY4066434, explicitly designated a pan-KRAS inhibitor in its trial title, is currently in a Phase I study (NCT06607185) in KRAS-mutant NSCLC, PDAC, and CRC that is listed as active but no longer recruiting. Treeline Biosciences’ TLN-372 is in a recruiting Phase I study (NCT07204340) in advanced KRAS-mutant solid tumors that also includes combination arms with cetuximab and pembrolizumab. What distinguishes KST-6051 from the approved G12C-selective covalent inhibitors — its claimed activity against the GTP-bound state — is a property it shares with other next-generation candidates in this cohort, but one that remains to be validated in human pharmacodynamic studies. Meta description: Kestrel Therapeutics opens first-in-human Phase I trial of pan-KRAS inhibitor KST-6051 in KRAS-mutant solid tumors. Your email address will not be published. Required fields are marked * Comment * Name * Email * Website