Early data for experimental DM1 therapy SRP-1003 coming soon
Phase 1/2 clinical trial recently hit first of two enrollment targets
Preliminary data are expected this year for a Phase 1/2 clinical trial testing the investigational therapy SRP-1003 in people with myotonic dystrophy type 1 (DM1), according to an announcement from Sarepta Therapeutics.
The trial recently hit one of two prespecified enrollment targets, prompting a review of safety data.
The Phase 1/2 study (NCT06138743) is being sponsored by SRP-1003’s original developer, Arrowhead Pharmaceuticals. In a deal that closed early this year, Sarepta acquired rights to take over the development of the therapy. As a milestone payment agreed upon in the deal, Sarepta owes $100 million to Arrowhead now that the trial has hit its first prespecified enrollment target.
To facilitate that payment, Arrowhead is redeeming $50 million worth of stock from Sarepta. In total, Sarepta expects to net at least $174 million in cash.
“We are very pleased with the progress of our potentially best-in-class siRNA programs, including the advancement of our SRP-1003 program for DM1, triggering the $100 million milestone payment to our partner, Arrowhead,” Doug Ingram, CEO of Sarepta, said in a company press release. “The sale of our equity investment is a strategic decision to help fund this milestone, but does not change our conviction in the utility of the siRNA approach and our confidence in the work Arrowhead is doing to apply this technology across several disease states.”
In a separate press release, Christopher Anzalone, PhD, president and CEO of Arrowhead, spoke about the payment.
“While we remain confident that Sarepta will meet its financial obligations to Arrowhead, we believe reducing our outstanding shares by receiving approximately half of the $100 million due from Sarepta in cash and half in Arrowhead stock to be returned to treasury is a compelling opportunity,” Anzalone said.
Data from trial testing ARO-DUX4 also expected this year
Small interfering RNA, or siRNA, are small pieces of genetic material that are designed to attach to messenger RNA, a type of molecule that has genetic information from DNA, and block it from delivering instructions to make proteins. SRP-1003, previously known as ARO-DM1, inhibits the production of a protein called DMPK, whose messenger RNA is abnormally long and forms toxic clumps in cells. DM1 is caused by mutations in the DMPK gene. Myotonic dystrophy is the most common form of muscular dystrophy.
The Phase 1/2 study is expected to enroll adults with DM1, ages 18 to 65. In a two-part design, participants will be randomly assigned to receive one or multiple doses of SRP-1003, or a placebo, with the main goal being evaluating the experimental treatment’s safety. Pharmacokinetics (how the treatment moves into, through, and out of the body) as well as pharmacodynamics (its effects on the body) will also be assessed. Enrollment is ongoing at sites in Australia, New Zealand, Taiwan, and Thailand.
Arrowhead has also developed another siRNA therapy called ARO-DUX4, which is designed to knock down production of the DUX4 protein in skeletal muscles, or those under voluntary control, that is abnormally produced in facioscapulohumeral muscular dystrophy (FSHD). Sarepta secured rights to ARO-DUX4 in the same deal that it acquired rights to SRP-1003. A Phase 1/2 clinical trial (NCT06131983) testing that therapy is ongoing, with early data also expected later this year.
“We look forward to sharing early data from our FSHD and DM1 programs in the second half of this year,” Ingram said.
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