Prosetin

ProJenX is a small private biotech in New York, set up to develop prosetin, which came out of research at Columbia University supported by the charity Project ALS. The ALS part of its trial is supported by a $1 million Hoffman award from the ALS Association, and the US Department of Defense ALS research programme is listed as a collaborator.

In ALS, clumps of the protein TDP-43 put nerve cells under stress. Lab research found that an enzyme called MAP4K drives motor neuron death under this kind of stress. Prosetin is designed to reach the brain and spinal cord and block MAP4K, to slow that loss of nerve cells.

PRO-101 tested single and repeated doses in healthy volunteers, then 14 days of rising doses against placebo in 41 people with ALS. Those who finished can keep taking prosetin in an open-label extension. In 2024 the FDA lifted a partial hold that had limited which doses could be used in the US. The FDA gave prosetin orphan drug status for ALS in 2020; that is not an approval. ProJenX says it is designing a Phase 2 trial but has not given a date.

In June 2026 ProJenX reported that prosetin was safe across all doses tested in people with ALS, with no drug-related serious side effects, and that blood levels at the top two doses reached the target range. A blood marker showed the enzyme was being blocked. The 14-day test was far too short to show any effect on ALS. The extension tracks NfL and the ALSFRS-R score but has no placebo group. Earlier lab and mouse results do not show it works in people; most drugs that work in mice do not. These results are from the company and conference posters, not a peer-reviewed paper.

This is the most favourable result reported. See all key studies for the full picture.

Researchers involved describe prosetin as a possible treatment for sporadic ALS, the common non-inherited form. In the trial it is taken by mouth as a liquid, with the dose based on body weight.

ProJenX presented long-term data at the NEALS meeting in late October 2026 and says it is using the extension data to design a Phase 2 trial. It has not given a start date.

PRO-101 is fully enrolled and no longer taking new people. Participants already in it can stay on prosetin in the extension. We found no expanded access programme.

• PRO-101 (Phase 1) (NCT05279755) active not recruiting · Boston MA, San Antonio TX, Montreal (Canada), Utrecht (Netherlands)