CytomX Therapeutics (NASDAQ:CTMX) plans to provide a January update on its lead cancer drug candidate, Varseta-M, as it prepares for a potential registrational study in metastatic colorectal cancer in the first half of 2027.
The update is expected to include the first look at overall survival data for Varseta-M, an antibody-drug conjugate targeting EpCAM, CEO and Chairman Sean McCarthy said on the company’s third-quarter 2026 earnings call. CytomX anticipates using overall survival as the primary endpoint in a randomized initial registrational study, though it has not finalized the patient population or comparator.
CytomX also reported $348 million in cash, cash equivalents and investments as of Sept. 30, including $37 million received from Regeneron under an expanded collaboration. CFO Chris Ogden said the company expects its current resources to fund operations into the second half of 2028.
January update to guide study design
Varseta-M’s phase 1 monotherapy study has enrolled more than 100 patients across dose escalation, expansion and optimization cohorts. Most participants had received at least three prior treatments for metastatic disease, McCarthy said.
The company is evaluating doses of 8.6 and 10 milligrams per kilogram every three weeks using adjusted ideal body weight dosing and upfront measures to prevent gastrointestinal adverse events. McCarthy said CytomX plans to share progression-free survival data from the optimization cohorts alongside the first overall survival results from escalation and expansion.
Asked why the update had shifted from year-end 2026 to January, McCarthy said the company wanted sufficient follow-up to assess safety and efficacy and time for engagement and feedback from regulators. CytomX has not specified the forum for the update or disclosed which dose it may select for a later-stage study.
McCarthy said the company is considering options for treating patients in the third-line or later setting. He noted that treatment in that population is fragmented and said CytomX is weighing both the appropriate patient group and comparator for its proposed study.
Diarrhea management remains a focus
McCarthy said CytomX aims to manage the rate of grade 3 diarrhea at 20% or below. In March, the company reported a 10% rate among the first 20 patients in dose optimization cohorts after two months of matched follow-up, compared with more than 30% among time-matched patients from escalation and expansion.
He said the previously reported time to onset of grade 3 diarrhea at the studied doses was about five weeks and that the toxicity did not appear to be cumulative. CytomX is also examining how long patients spend with grade 3 symptoms and the overall burden, McCarthy said.
The company hopes that managing diarrhea will help maintain dose intensity, which McCarthy said could be important to efficacy over time.
Combination and broader tumor studies
CytomX is enrolling late-line colorectal cancer patients in a phase 1 study of Varseta-M with bevacizumab and expects initial clinical data in the first half of 2027.
It also plans to start a phase 1/2 study by the end of 2026 combining Varseta-M with bevacizumab, five-fluorouracil and leucovorin. McCarthy said the initial dose-finding portion will most likely enroll late-stage patients; the phase 2 portion would enroll second-line patients after successful dose finding.
In that regimen, the company’s strategy is to replace irinotecan with Varseta-M, McCarthy said. He identified gastrointestinal toxicity, particularly in combination with five-fluorouracil, as an area the company will watch closely.
CytomX has also started phase 1 cohorts in gastric and gastroesophageal junction cancers, as well as EpCAM-selected pancreatic ductal adenocarcinoma and biliary tract cancer. It initially plans to enroll approximately 20 patients per tumor type to evaluate safety and antitumor activity.
Separately, the company continues to enroll a phase 1 study of CX-801, its masked interferon alpha-2b candidate, alone and with Keytruda in checkpoint-refractory melanoma. Initial clinical data are expected in the first half of 2027.
Third-quarter financial results
Third-quarter revenue fell to $1.7 million from $6 million a year earlier, primarily because the Astellas collaboration concluded in the second quarter of 2026, Ogden said.
Operating expenses rose to $25.2 million from $21.7 million. Research and development expenses increased by $1.2 million to $16.5 million, while general and administrative expenses rose to $8.7 million from $6.4 million, primarily because of personnel-related costs and higher consulting spending.
About CytomX Therapeutics (NASDAQ:CTMX)
CytomX Therapeutics, Inc is a clinical-stage biopharmaceutical company focused on developing cancer medicines designed to be activated selectively within the tumor microenvironment. The company’s approach is intended to improve the precision of treatment by limiting activity in healthy tissues while enabling therapeutic effects at tumor sites.
CytomX’s research is based on its Probody therapeutic platform, which uses molecular masking and tumor-associated protease activity to conditionally activate antibody-based medicines.
