By Mackenzie Tatananni

A small-cap biotechnology stock was floundering Monday after flaws in a trial design rendered survival data for a groundbreaking cancer drug statistically insignificant.

Boston-based Compass Therapeutics said its biliary cancer treatment successfully delayed the progression of the disease, but due to the study's design, long-term survival data remains inconclusive.

Shares cratered 61% to $1.97, putting Compass stock on pace for its largest single-day percentage drop on record, according to Dow Jones Market Data. The benchmark S&P 500 was down slightly.

The biotechnology company was testing a combination of its lead asset, tovecimig, and paclitaxel in patients with biliary tract cancer. Paclitaxel is a well-established, frontline standard of care for several cancers.

The study met its goal for progression-free survival, meaning it successfully delayed disease progression or death from any cause. Patients taking the tovecimig combination stayed stable for 4.7 months, compared with only 2.6 months for those taking paclitaxel alone.

However, the combined treatment didn't meet the overall survival target thanks to confounded data. More than half of patients receiving paclitaxel alone ended up switching over to start taking tovecimig.

The median overall survival of crossover patients was 12.8 months versus 6.1 months for those taking paclitaxel alone, Compass said. However, the data can't be considered statistically significant given the trial design.

The hurdle comes just as Compass seemed to be finding its stride. Heading into 2026, the outlook was bright -- CEO Thomas Schuetz hailed 2025 as a breakthrough year after tovecimig delivered positive trial results. However, with no products on the market, the company finds its path to commercialization under renewed pressure.

ABL Bio, a Korean biotech, developed tovecimig and licensed it to Compass for development in other regions. In November, ABL said U.S. regulators had granted the treatment orphan drug designation. This status is reserved for drugs that address rare conditions and require government incentives to be financially viable.

Despite the recent setback, Compass is still seeking a Biologics License Application for tovecimig. The company expects to meet with the Food and Drug Administration in the coming months to discuss the underlying data.

Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com

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April 27, 2026 12:29 ET (16:29 GMT)

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