Intellia Therapeutics, Inc. and Regeneron Pharmaceuticals, Inc. announced additional positive interim data from an ongoing Phase 1 study of their lead investigational in vivo genome editing candidate, NTLA-2001, which is being developed as a single-dose treatment for transthyretin (ATTR) amyloidosis. The data were presented in an oral presentation at the European Association for the Study of the Liver (EASL) International Liver Congress 2022, taking place June 22 26 in London. The presentation included extended follow-up data from 15 patients with hereditary ATTR amyloidosis with polyneuropathy (ATTRv-PN) treated across four single-ascending dose cohorts in Part 1 of the study.
Results demonstrated sustained durability of serum transthyretin (TTR) reduction through the last measured timepoint in the ongoing observation. These data support NTLA-2001's continued development as a potential one-time treatment to permanently inactivate the TTR gene and reduce the disease-causing protein. At the highest dose evaluated, treatment with NTLA-2001 at 1.0 mg/kg resulted in a 93% mean and 98% maximum serum TTR reduction by day 28 across the six patients treated.
With longer-term follow-up data now available, these deep reductions continue to be sustained through six months, with an observed mean reduction of 93%. Additionally, three patients in the 1.0 mg/kg cohort have reached nine months in the follow-up period with no evidence of a loss in TTR reduction after a single dose. In the 0.7 mg/kg dose cohort, the 86% mean serum TTR reduction observed at day 28 also remained durable through six months.
Further, in the 0.1 and 0.3 mg/kg cohorts, patients have now reached 12 months of follow-up, and a durable response to treatment continues to be observed. Notably, patients in the 0.3 mg/kg cohort sustained an 89% mean serum TTR reduction at 12 months. At all four dose levels, NTLA-2001 was generally well tolerated through the follow-up period (median follow-up of 10 months).
The majority of adverse events were mild in severity with 73% (n = 11) of patients reporting a maximal adverse event severity of Grade 1. There was a single possibly related serious adverse event of vomiting (Grade 3) reported in a patient with concomitant medical history of gastroparesis in the 1.0 mg/kg dose group. The most frequent adverse events included headache, infusion-related reactions, back pain, rash and nausea. All infusion-related reactions were considered mild, resolving without clinical sequelae.
The safety and activity profile of NTLA-2001 observed in Part 1 indicates that NTLA-2001 has a favorable therapeutic window. These data combined with pharmacokinetic modeling and simulation data support the utilization of a fixed dose of 80 mg in Part 2, which is anticipated to yield similar exposures to the 1.0 mg/kg dose. Dosing is ongoing in Part 2, the single-dose expansion cohort of the polyneuropathy arm.
The Phase 1 study, run by Intellia as the program's development and commercialization lead as part of a multi-target collaboration with Regeneron, is evaluating NTLA-2001 in patients with either ATTRv-PN or ATTR amyloidosis with cardiomyopathy (ATTR-CM). The cardiomyopathy arm, evaluating NTLA-2001 across patients classified with New York Heart Association (NYHA) Class I - III heart failure, is ongoing. The companies plan to present the first interim data from the cardiomyopathy arm in the second half of 2022.
Enrollment across both ATTRv-PN and ATTR-CM patient populations is expected to complete in 2022.