Setback in ALS Drug Trial: Denali/Sanofi's Phase 2 Study Fails to Meet Primary Endpoint

In a recent development, Denali Therapeutics and Sanofi's collaborative phase 2 clinical trial for a potential amyotrophic lateral sclerosis (ALS) treatment has encountered a significant setback. The trial, which evaluated the efficacy of the RIPK1 inhibitor SAR443820/DNL788, failed to achieve the primary endpoint based on the ALS Functional Rating Scale-Revised (AL-SFRS-R). This disappointing outcome has led to an initial 8% drop in Denali's stock price. Let's delve into the details of this trial and its implications for ALS research.

ALS, also known as Lou Gehrig's disease, is a rare neurodegenerative disorder that affects the nerve cells responsible for controlling voluntary muscles. Currently, there are limited treatment options available for ALS patients, with only three drugs approved by the U.S. Food and Drug Administration (FDA): Radicava, Riluzole, and Relyvrio.

The phase 2 trial, named Himalaya, aimed to assess the potential of SAR443820/DNL788, a selective and brain-penetrant RIPK1 small molecule inhibitor, in treating ALS. RIPK1 is a key signaling protein in the tumor necrosis factor receptor pathway, regulating inflammation and cell death. Increased RIPK1 activity in the brain leads to neuroinflammation, cell death, and neurodegeneration, making it a potential target for ALS and other neurodegenerative diseases.

However, despite promising preclinical data, the phase 2 trial did not demonstrate the desired therapeutic effect as measured by the AL-SFRS-R. Denali and Sanofi had previously collaborated on a phase 2 trial evaluating SAR443820/DNL788 for the treatment of multiple sclerosis (MS), which also failed to meet expectations. The companies had plans to advance the drug into phase 3 clinical trials later this year, but these plans are now uncertain following the trial's disappointing results.

The collaboration between Denali and Sanofi dates back to November 2018 when they announced a partnership to develop multiple RIPK1 inhibitors. The agreement provided Denali with an initial funding of $125 million and potential milestone payments exceeding $1 billion. DNL747 and DNL758 were the primary candidates for development. DNL747, a brain-penetrant RIPK1 small molecule inhibitor, targeted ALS, Alzheimer's disease, and MS, while DNL758, a non-brain-penetrant RIPK1 small molecule inhibitor, focused on systemic inflammatory diseases such as rheumatoid arthritis and psoriasis.

In addition to the setback in the SAR443820/DNL788 trial, Denali is also advancing another late-stage candidate, DNL343, for the treatment of ALS. DNL343 is a first-in-class drug designed to modulate the activity of eIF2B, a protein complex essential for neuronal health and function. By activating eIF2B, DNL343 aims to restore protein synthesis, disperse TDP-43 aggregates, and improve neuronal survival.

The failure of Denali and Sanofi's phase 2 ALS drug trial is a significant setback for ALS research and the quest for effective treatments. Despite the challenges faced in developing therapies for ALS, ongoing research and the exploration of novel targets such as RIPK1 and eIF2B offer hope for future breakthroughs. Continued efforts to understand the complex mechanisms underlying ALS and innovative approaches to drug development are crucial in the pursuit of effective treatments for this devastating disease.