Intellia Therapeutics, Inc. presented additional interim results from its ongoing Phase 1 study of NTLA-2001, an investigational, in vivo CRISPR/Cas9 genome editing therapy in development as a single-dose treatment for transthyretin (ATTR) amyloidosis. Results were presented in an oral presentation at the 4th International ATTR Amyloidosis Meeting, held Nov. 2?3 in Madrid, Spain.

In the newly reported dose-expansion portion, administration of NTLA-2001 at the 55 mg and 80 mg dose led to deep serum TTR reductions consistent with the results previously reported [1] from patients in the dose-escalation portion who received the corresponding weight-based dose, 0.7 mg/kg and 1.0 mg/kg, respectively. Across all patients who received a dose of 0.3 mg/kg or higher (n=62), the median serum TTR reduction was 91% and the median absolute residual serum TTR concentration was 17 µg/mL at day 28. The persistently low levels of TTR concentration are expected to reduce the rate of ongoing amyloid formation and hold the possibility for amyloid clearance to reverse the symptoms of the disease.

If clinically validated, the use of absolute residual TTR concentration levels could become a new benchmark for evaluating ATTR amyloidosis. The reduction of serum TTR compared to baseline was sustained through the latest follow-up. With 29 patients now reaching at least 12 months of follow-up, all patients continued to show a long-lasting response with no evidence of loss in activity over time.

NTLA-2001 was generally well tolerated across all patients and at all dose levels tested. The most commonly reported adverse events were infusion-related reactions, which occurred in 38% of patients. The majority of adverse events, including infusion-related reactions, were Grade 1 or 2 in severity, transient and resolved spontaneously.

Other adverse events that were reported in greater than 10% of patients included headache, diarrhea and back pain, and were all Grade 1 or 2. All patients received a full dose of NTLA-2001 and remain on study. No dose-limiting toxicities were observed. Based on the safety and activity of NTLA-2001, the 55mg dose has now been selected to be evaluated in the upcoming pivotal Phase 3 study.

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 in people living with ATTR amyloidosis. As previously announced [2], Intellia recently received IND clearance from the FDA to begin a Phase 3 trial of NTLA-2001 for ATTR-CM and expects to initiate the global pivotal trial by the end of this year. Additionally, the Company is actively preparing for a Phase 3 trial for ATTRv-PN.