Janux Therapeutics' stock value soared after early trial results suggested its immunotherapy technology could offer potent, safer treatments for solid tumors. Its drugs, aimed at conditions like metastatic prostate cancer, showed promising safety and efficacy profiles, with notable results in lowering cancer markers without severe side effects. The approach involves T cell engagers designed to target cancer cells while sparing healthy tissue. Positive outcomes, particularly against prostate cancer, position Janux competitively against major pharmaceutical companies. Further updates are expected later this year.

The following article originally appeared in BioPharma Dive.

Janux is trying a twist on a kind of immunotherapy drug that’s proven effective in certain cancers, but has been limited by safety risks in others.

Known alternatively as T cell engagers or as bispecifics, this type of drug brings immune cells into contact with cancerous cells — an introduction that helps those immune cells recognize and destroy a tumor. The drugs can do this by binding to different protein targets that are found on the surface of each respective cell.

The problem is that these targets can also be found on healthy cells, too, resulting in side effects that necessitate lower doses or, in some cases, make treatment impractical. Janux’s approach is to create a sort of mask that stops its T cell engagers from making their deadly introduction in healthy tissue. In and around tumors, however, these masks are cast off, allowing the drugs to do their work.

The data released Monday are the most convincing evidence yet in support of Janux’s hypothesis.

“Previously, [Janux] has shown supportive pharmacodynamics on their masking technology — an essential first step, but in the context of a very active [prostate cancer] space it wasn’t a clear standout,” wrote Evercore’s Miller. “Data this evening, on the other hand, makes a big splash.”

Analysts at Cowen and William Blair also saw the results as validating, especially in the prostate cancer setting. There, Janux has competition from large companies like Amgen, Regeneron and Johnson & Johnson, which are also developing T cell engagers that are aimed at the same target, a protein called PSMA, as Janux’s.

Yet Janux’s results, while early and from only a small number of people, suggest its drug could have fewer serious safety risks. None of the 23 treated participants with metastatic castration-resistant prostate cancer experienced severe cases of an immune side effect known as cytokine release syndrome, or CRS, for instance.

Efficacy results, meanwhile, showed treatment led to substantial decreases in a prostate cancer marker that’s indicative of benefit. At higher doses Janux tested, all six treated participants had a 30% or higher decrease in this marker, known as prostate-specific antigen. Five had a 50% or higher decline, and one had a greater than 90% decline.

“The present data — which show impressive PSA response rates coupled with mild and manageable CRS — represent a substantial win for Janux and are beyond even our best case scenario,” Marc Frahm, an analyst at Cowen, wrote in a client note.

Analysts noted that further data are needed to better characterize the effect of Janux’s drug in prostate cancer, especially as different doses are tested. The company plans to provide an update in the second half of the year.

Janux’s other drug, aimed at different cancer cell target, was tested in 11 patients with different kinds of solid tumors. There were no dose-limiting toxicities or serious side effects linked to treatment, according to the company.

Janux had about $350 million in cash on hand as of September, funds that should allow it to operate into 2027. The company went public in June 2021, raising $194 million.

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