CTMX Stock Rallies on Strong Phase I Colorectal Cancer Study Data

Shares of CytomX Therapeutics CTMX soared 44.2% on Monday after the company reported positive phase I expansion data for its EpCAM-targeting PROBODY ADC, varsetatug masetecan (Varseta-M), in late-line metastatic colorectal cancer (CRC) from the ongoing CTMX-2051-101 study.

Patients in the study were heavily pretreated, having received a median of three prior metastatic therapies, and 96% had prior irinotecan exposure. Out of the total enrolled population, 76% had liver metastases and 71% carried KRAS mutations. Although patients were not selected based on EpCAM expression, all evaluable tumor biopsies showed high EpCAM levels.

CTMX’s Phase I Colorectal Cancer Study Data in Detail

In the phase I expansion portion of the CTMX-2051-101 study, CytomX Therapeutics reported encouraging efficacy signals for Varseta-M in patients with heavily pretreated metastatic CRC. As of Jan. 16, 2026, data cutoff, 56 patients across the 7.2 mg/kg, 8.6 mg/kg and 10 mg/kg dose cohorts were evaluable for efficacy, out of the enrolled 60, with a median follow-up of about eight months. The therapy demonstrated increasing activity at higher dose levels, with confirmed overall response rates of 6% at 7.2 mg/kg, 20% at 8.6 mg/kg and 32% at 10 mg/kg.

Progression-free survival also improved with dose escalation. Median progression-free survival was 5.5 months at 7.2 mg/kg, rising to 6.8 months at 8.6 mg/kg and 7.1 months at the 10 mg/kg dose. Disease control rates remained high across cohorts, reaching 88% overall across the expansion population, suggesting the therapy was able to stabilize disease in a large proportion of treated patients.

In the past six months, CTMX shares have skyrocketed 230.9% compared with the industry’s 14.5% growth.Zacks Investment Research

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Based on these results, the 8.6 mg/kg and 10 mg/kg regimens have been prioritized for further evaluation as CytomX Therapeutics works to identify a potential dose or doses for a registrational study. Dose-optimization efforts using adjusted ideal body weight dosing and updated prophylaxis for adverse-event management are ongoing.

Varseta-M demonstrated a generally manageable safety profile in the phase I study, consistent with interim clinical data reported last year, with most treatment-related adverse events reported as mild to moderate in severity. One treatment-related severe acute kidney injury occurred earlier in the study in a patient with a complex medical history, with no additional severe events observed as of the January 2026 data cutoff.

CTMX’s Next Steps in the Development of Varseta-M

CytomX Therapeutics plans to continue advancing Varseta-M through clinical development, with additional efficacy and safety data from the ongoing phase I advanced CRC study expected to be presented at medical meetings in 2026. The company also intends to engage with the FDA during the year to discuss a potential registrational study design evaluating Varseta-M monotherapy in advanced CRC. In this setting, patients currently have limited treatment options.

Story Continues

In parallel, CytomX Therapeutics is exploring combination strategies to broaden the therapy’s clinical potential. A phase I study evaluating Varseta-M in combination with Roche’s Avastin (bevacizumab) in CRC has already been initiated. A phase Ib/II study combining Varseta-M with Avastin and chemotherapy is also expected to begin by the end of 2026. The company is also planning to launch phase I expansion cohorts in additional EpCAM-expressing cancers in the second half of 2026.

CytomX Therapeutics, Inc. Price and ConsensusCytomX Therapeutics, Inc. Price and Consensus

CytomX Therapeutics, Inc. price-consensus-chart | CytomX Therapeutics, Inc. Quote

CTMX’s Zacks Rank & Stocks to Consider

CytomX Therapeutics currently carries a Zacks Rank #3 (Hold).

Some better-ranked stocks in the biotech sector are Castle Biosciences CSTL, Catalyst Pharmaceuticals CPRX and ALX Oncology Holdings ALXO. While USNA and CPRX sport a Zacks Rank #1 (Strong Buy) each, ALXO carries a Zacks Rank #2 (Buy) at present. You can see the complete list of today’s Zacks #1 Rank stocks here.

Over the past 60 days, estimates for Castle Biosciences’ 2026 loss per share have narrowed from $1.11 to $1.06. CSTL shares have gained 10.1% over the past six months.

Castle Biosciences’ earnings beat estimates in three of the trailing four quarters and missed in the remaining one, with the average surprise being 34.69%.

Over the past 60 days, estimates for Catalyst Pharmaceuticals’ 2026 earnings per share have risen from $2.55 to $2.82. CPRX shares have gained 14.2% over the past six months.

Catalyst Pharmaceuticals’ earnings beat estimates in each of the trailing four quarters, with the average surprise being 35.19%.

Over the past 60 days, estimates for ALX Oncology Holdings’ 2026 loss per share have narrowed from $1.21 to 90 cents. ALXO shares have surged 90.8% over the past six months.

ALX Oncology Holdings’ earnings missed estimates in each of the trailing four quarters, with the average negative surprise being 12.82%.

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This article originally published on Zacks Investment Research (zacks.com).

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