Dive Brief:A single infusion of a CRISPR therapy developed by Intellia Therapeutics showed promising signs of stabilizing a heart disorder caused by the rare disease transthyretin amyloidosis, buoying the companys hopes of finding success in late-stage clinical trials.Phase 1 study data from 36 people with the cardiomyopathy form of transthyretin, or ATTR, amyloidosis showed Intellias gene editing treatment sharply and durably lowered levels of the ATTR protein that misfolds and gathers in the toxic clumps that characterize the disease.Prior trial results, in fewer people and across shorter periods of time, had already shown Intellias therapy capable of reducing ATTR protein. The new findings, which were published Friday in The New England Journal of Medicine, show those reductions appeared to translate to stability or improvement on several markers of cardiac disease progression, too.Dive Insight:Intellia Therapeutics has, along with several of its peers, been at the forefront of the biotechnology industrys efforts to translate breakthrough CRISPR science into real medicines. CRISPR Therapeutics reached that milestone first with Casgevy, a sickle cell disease therapy thats built from gene edited stem cells.But Intellia has been the standard bearer for whats known as in vivo CRISPR editing. Rather than use CRISPR to create a medicine from, say, a patients own cells, in vivo editing means the CRISPR components are themselves the therapy, delivered directly into the body where they do their DNA-modifying work.Intellias amyloidosis medicine, now dubbed nex-z, works by using CRISPR to knock out a gene thats responsible for making the TTR protein in the liver. Its meant to be a one-time treatment that permanently turns off TTR protein production, thereby preventing further damage to the heart and nerves.The data published in NEJM Friday are the best look yet at nex-zs potential and offer encouraging signs. Nex-z reduced TTR protein levels by 90%, compared to baseline, at one year. Among the 11 patients who have been followed for two years, TTR levels remained low and virtually unchanged, the study authors wrote.Importantly, that reduction led to stabilization or improvement on three measures of heart disease progression and heart failure classification. On the last measure, for instance, 47% of participants improved by at least one class on a New York Heart Association rating scale. Only 8% of participants experienced a worsening of their NYHA class.Five patients had infusion-related reactions to nex-z, while two experienced increases in liver enzyme counts that resolved without medical intervention, according to the NEJM paper. One of the infusion reactions was judged to be severe by investigators and led to a overnight stay in the hospital for observation.While this current study didnt involve a placebo, Intellia is running a Phase 3 study in about 750 people with cardiomyopathy due to ATTR amyloidosis that will test nex-z against placebo on cardiovascular mortality and heart events.Success in that trial could position Intellia to seek regulatory approval. But even then, nex-z would be entering a market with potentially three different drugs already cleared. Pfizers Vyndamax has been on the market for several years, while BridgeBio Pharma and Alnylam Pharmaceuticals aim to win Food and Drug Administration OKs for their rival medicines this month and next year, respectively.All of those drugs need to be taken chronically, which could favor nex-z and its one-time infusion. But their comparative efficacy is already a matter of serious debate, as doctors weigh the drugs respective data. Nex-z would be no different.I think people will need to know what is the most efficacious, which actually prevents not only heart failure, but any other adverse cardiovascular events associated with amyloid deposition in the heart and, in fact, which is the most durable over time, said Jane Leopold, NEJMs deputy editor, in an audio interview on Intellias data.Shares in Intellia oscillated in Monday morning trading. '