CytomX Therapeutics (CTMX) investor relations material

Masking platform and pipeline

• Masking limits biologic binding in healthy tissue and favors activation in tumors, enabling pursuit of targets that may otherwise be difficult to drug.

• Clinical focus includes Varseta-M, an EpCAM-targeted ADC for colorectal cancer (CRC), and masked interferon alfa-2b for melanoma.

• EpCAM was selected for its abundance in CRC tumors; earlier antibody and T-cell engager approaches encountered toxicity including pancreatitis, liver toxicity and GI effects.

• Varseta-M uses a Topo-1 payload selected for CRC activity; its DAR 8 design was benchmarked against ENHERTU’s deruxtecan ADC profile.

Varseta-M efficacy and tolerability

• In heavily pretreated, fourth-line-or-later CRC, Phase I response rates were 20%-30% and estimated PFS was 6-7 months, versus 1%-2% response rates and only a few months’ PFS with later-line standard benchmarks.

• Initial OS reads are expected later in 2026; the observed activity supports advancing Varseta-M to late-phase development.

• Grade 3 diarrhea exceeded 20% and reached the 30% range at higher doses; dual prophylaxis with loperamide and budesonide reduced the rate to 10% in an early update after two months’ follow-up, versus ~30% without prophylaxis.

• The goal is to manage grade 3 diarrhea at 10%-20%; adjusted ideal body weight dosing is intended to limit high-BMI exposure outliers, with further data expected later in 2026.

• Dose selection and registration planning will incorporate FDA discussions under Project Optimus; the base plan is to report supporting data and next steps together, subject to FDA interactions.

Registration and combination strategy

• The first monotherapy registration study is expected to be randomized with an OS endpoint; options under consideration are later-line treatment versus third-line treatment, with relevant standard-of-care comparators.

• Bevacizumab combination dose-finding began in late Q1 or Q2 2026; initial safety, dose, schedule and early efficacy data are expected in H1 2027.

• A Varseta-M, bevacizumab and 5-FU triplet is planned to start in Q4 2026, aiming to replace irinotecan in FOLFIRI plus bevacizumab and potentially enable earlier-line use.

• Combination development carries forward adjusted ideal body weight dosing and diarrhea prophylaxis; schedules are being evaluated to align with bevacizumab every two weeks.

• A fourth-line launch opportunity was estimated at more than $1 billion; the stated strategy is to move upstream as combination evidence develops.