Los Angeles-based Kairos Pharma, Ltd. (NYSE American: KAPA) revealed the signing of a binding terms sheet to acquire exclusive worldwide rights to CL-273, an investigational, reversible, wild-type-sparing pan-EGFR small-molecule inhibitor, from the Delaware-based Celyn Therapeutics Inc.

According to the firm’s press release Kairos will take full global development and commercialization rights to CL-273, with no upfront or milestone payments disclosed. Instead, Celyn will receive Kairos Pharma shares equivalent to 16.5% of the company on a fully diluted basis at closing. A single regulatory milestone of USD 15 million, payable in a combination of cash and shares, is triggered upon US FDA NDA submission. Celyn will also receive a 2% royalty on US net revenues for the life of the applicable intellectual property. No development milestones, additional regulatory milestones, or commercial sales milestones were disclosed. The royalty is limited to US net revenues, meaning Kairos retains 100% of ex-US commercial economics beyond the indirect exposure Celyn holds through its equity stake.

CL-273 was designed using Celyn’s proprietary AI-driven drug discovery platform and is intended for EGFR-mutant non-small cell lung cancer (NSCLC), including tumors that have developed resistance to existing EGFR tyrosine kinase inhibitors. The deal also encompasses CL-741, a Phase I-ready c-MET inhibitor from Celyn’s pipeline, though specific separate financial terms for that asset were not disclosed.

Kairos Pharma CL-273: Mechanism, Disease Rationale, and Development Status

CL-273 is a pre-IND stage small-molecule kinase inhibitor engineered to bind across multiple EGFR mutant forms while sparing wild-type EGFR, a profile intended to reduce the dose-limiting toxicities — primarily rash and diarrhea — that constrain exposure with earlier-generation EGFR inhibitors. The compound targets resistance mutations that emerge following treatment with approved EGFR tyrosine kinase inhibitors such as osimertinib (AstraZeneca’s Tagrisso), which is the current standard of care in first-line EGFR-mutant NSCLC. Resistance to osimertinib develops through heterogeneous mechanisms including C797S mutations, MET amplification, and other bypass pathway activation, creating a pan-EGFR lung cancer treatment gap that multiple companies are now attempting to address. EGFR mutations are present in approximately 10%-15% of NSCLC cases in Western populations and up to 50% in East Asian populations.

Prior to this transaction, Kairos Pharma’s pipeline was centered on a single platform asset: ENV-105 (carotuximab), a monoclonal antibody targeting CD105 (endoglin), a protein implicated in drug resistance and immune suppression in cancer. ENV-105 is currently in a Phase II study for castrate-resistant prostate cancer) and Phase I in NSCLC. The rights to ENV-105 were acquired by Kairos through a 2021 partnership with Tracon Pharmaceuticals. The addition of CL-273 and CL-741 has been framed by Kairos as enabling a potential combination strategy across EGFR and MET pathways.