CytomX Therapeutics (CTMX) 3rd Annual Guggenheim Healthcare Innovation Conference summary

PROBODY platform and varseta-M

• PROBODY masks biologics with peptide sequences that tumor proteases cleave, aiming to localize activity in the tumor microenvironment and reduce peripheral activity.

• EpCAM is highly expressed across CRC and other solid tumors; prior systemic approaches faced normal-tissue toxicity, including acute pancreatitis.

• Varseta-M (CX-2051; varsetatug masetecan) is a masked EpCAM ADC with a topoisomerase I payload, designed to open a therapeutic window for systemic EpCAM targeting.

CRC data and dose optimization

• March update in 4L+ CRC showed 20%-30% response rates and 6-7 months’ PFS; first OS data are planned for the next update.

• Benchmarks cited: 4L fruquintinib or regorafenib, 1%-2% response rates, ~3 months’ PFS and ~5-6 months’ OS; 3L bevacizumab/LONSURF, ~5% response rate, ~5 months’ PFS and 9-10 months’ OS.

• No acute pancreatitis, pancreatic enzyme elevations or ILD observed to date; hematologic toxicity was low, while Grade 3 diarrhea declined from ~30% in expansion to ~10% in the first 20 optimization patients’ initial follow-up.

• Optimization cohorts are testing 8.6 and 10 mg/kg Q3W, with adjusted ideal body weight dosing and upfront loperamide/budesonide prophylaxis to manage diarrhea.

• Jan 2027 update expected to include OS from earlier cohorts, optimization-cohort safety, ORR and PFS, plus FDA interactions and direction for the next development stage; Phase I enrollment reached 113 patients.

Development plans and competitive landscape

• First pivotal CRC study is being evaluated for 3L+ or later disease, with OS anticipated as the primary endpoint; options include physician’s choice of fruquintinib/regorafenib or a head-to-head comparison with bevacizumab/LONSURF.

• The U.S. 3L+ CRC market was estimated at 35,000 treatable patients annually; future plans include combinations and movement into earlier treatment lines.

• Bevacizumab combinations are under exploration; work with 5-FU is targeted to start by end-2026. The program has expanded into gastric, gastroesophageal, pancreatic and biliary tract tumors.

• Differentiation cited versus other CRC ADCs includes low hematologic toxicity and no ILD to date; CDH17 ADC development was described as crowded, while varseta-M was characterized as the only clinical EpCAM ADC program with an intrinsically differentiated profile.