Vertex Pharmaceuticals may have narrowed its focus this year, but the biopharma’s decision to stick with its remaining islet cell therapy appears to be paying off so far.
The allogeneic human stem cell–derived islet cell therapy, called zimislecel, is being evaluated in an ongoing phase 1/2/3 study in patients with Type 1 diabetes with impaired hypoglycemic awareness and who suffer from severe hypoglycemic events, a term for dangerously low blood sugar levels. At the American Diabetes Association conference in Chicago last week, Vertex shared what it claimed were “unprecedented” data from 12 patients in the phase 1/2 portion of the study who received the full infusion of zimislecel and were followed up for a year.
The stem-cell-derived islets were engrafted successfully to all 12 patients, producing glucose-responsive endogenous C-peptide up to the one-year follow-up, Vertex said.
None of the patients experienced any severe hypoglycemic events from day 90 onward, with glycated hemoglobin (HbA1c) levels—a measure of diabetes control—at the recommended level of less than 7%, hitting the primary endpoint of the phase 1/2 portion of the study.
Meanwhile, 10 of the 12 patients no longer required insulin replacement therapy by the 12-month checkup, Vertex noted.
While two patients involved in the trial died, Vertex stressed that these fatalities were “both unrelated to treatment with zimislecel.” The treatment was “generally well tolerated,” the company added, with no serious adverse events linked to the therapy itself.
“These data on the first fully differentiated, stem cell-derived, off-the-shelf islet cell therapy continue to be unprecedented,” Vertex Chief Medical Officer Carmen Bozic, M.D., said in a June 20 release.
“The magnitude, consistency and durability of the results from all 12 patients with more than one year of follow-up reinforce the transformative potential of zimislecel for people living with T1D complicated by severe hypoglycemia,” Bozic added. “We are excited to complete enrollment and dosing in the phase 1/2/3 program and look forward to potential regulatory submissions next year.”
Zimislecel is Vertex’s only remaining clinical-stage islet cell treatment in development after the company ended work on VX-264 last month. A 90-day analysis of a phase 1/2 study of VX-264—which involved creating insulin-producing cells and surgically implanting them into people with Type 1 diabetes—had not produced the levels of a key biomarker for insulin production that had been hoped for.
At the time, William Blair analysts described the discontinuation of VX-264 as “disappointing given that this would have expanded Vertex’s type 1 diabetes market significantly from that being addressed from zimislecel.”
Unlike VX-264, zimislecel is administered along with immunosuppressants to help the cells graft. The phase 3 portion of the zimislecel study is running in the U.S., Canada, the U.K. and the EU, with approval applications to regulators penciled in for next year.
Scrapping VX-264 was only part of Vertex’s wider efforts this year to streamline its pipeline. The biopharma—which is in the process of launching its approved sickle cell disease and beta thalassemia gene therapy Casgevy—has also recently shifted away from adeno-associated virus vectors as a delivery mechanism for its genetic medicines.