CytomX Continues Phase I ADC Study After Patient Death
CytomX confirmed the death of a colorectal cancer patient in its Phase I trial of the anti-EpCAM ADC (CX-2051/varsetatug masetecan), due to treatment-related acute kidney injury believed to have resulted from severe nausea, vomiting, and diarrhoea135.
The company became aware of the adverse event on July 11, 2025, reported it to the FDA a week later, and later addressed the issue publicly after market speculation15.
Despite the Grade 5 (fatal) treatment-related event, the Phase I study continues with support from the Safety Review Committee, and patients are still being dosed across all planned expansion doses5.
Loperamide prophylaxis was previously implemented to mitigate diarrhoea toxicity, but it did not prevent this fatal event1.
A total of 73 colorectal cancer patients have been enrolled in the study, and CytomX remains on track to provide an updated data readout in Q1 20265.
Earlier interim data, reported in May 2025, had shown encouraging response rates and a manageable safety profile, with no dose-limiting toxicities at that time24.
Investor sentiment temporarily dipped on news of the death, but the stock partially recovered after CytomX clarified its ongoing clinical plans and trial continuation1.
Sources:
1. https://www.oncologypipeline.com/apexonco/cytomx-has-tox-wobble
2. https://www.globenewswire.com/news-release/2025/05/12/3078935/37704/en/CytomX-Announces-Positive-Interim-Data-From-Phase-1-Dose-Escalation-Study-of-EpCAM-Antibody-Drug-Conjugate-CX-2051-Candidate-in-Patients-with-Advanced-Colorectal-Cancer-CRC.html
3. https://sfbn.org/san-francisco-biotech-news/2025/08/13/cytomx-discloses-patient-death-in-study-of-adc-in-colorectal-cancer/
4. https://www.stocktitan.net/news/CTMX/cytom-x-announces-positive-interim-data-from-phase-1-dose-escalation-iyg4f0zfoxn2.html
5. https://www.stocktitan.net/news/CTMX/cytom-x-therapeutics-provides-update-on-cx-2051-phase-1-oro05fsv2w1r.html