Arrowhead Pauses ARO-ENaC Phase 1/2 Clinical Study

PASADENA, Calif. – Arrowhead Pharmaceuticals Inc. (NASDAQ: ARWR) today notified regulatory agencies, institutional review boards, and investigators that effective immediately it is voluntarily pausing AROENaC1001, a Phase 1/2 clinical study of ARO-ENaC, the company’s investigational RNA interference (RNAi) therapeutic being developed as a treatment for patients with cystic fibrosis (CF), after receiving a preliminary update from an ongoing chronic toxicology study in rats that contained unexpected signals of local lung inflammation. The company has instructed investigators to pause new screening, enrollment, and any further dosing of investigational ARO-ENaC pending additional data from the ongoing chronic rat toxicology study and an additional ongoing chronic primate toxicology study.

Javier San Martin, M.D., chief medical officer at Arrowhead, said: “The safety of patients that participate in clinical trials of our investigational medicines is paramount to us at Arrowhead. While we have not seen any concerning safety or tolerability signals in subjects enrolled in the AROENaC1001 study, out of an abundance of caution we have decided to pause new screening, enrollment, and any further dosing of investigational ARO-ENaC in the study while we await additional information from ongoing nonclinical toxicology studies. After we receive the full data from these studies, we will assess whether there is an acceptable path forward for further clinical investigation. While we determine our next steps with ARO-ENaC, we look forward to continued progress with the other 8 clinical drug candidates in our pipeline as well as our rapidly expanding preclinical initiatives, including additional lung-targeted programs.”

Christopher Anzalone, Ph.D., president and CEO at Arrowhead, said: “This is difficult news for cystic fibrosis patients who are in need of new therapeutic options, but we place above all else our obligation to ensure the safety of those enrolled in our clinical trials. Even though the preliminary information we received from the chronic toxicology study in rats may not necessarily bear directly upon the safety of continuing the current Phase 1 study, we believe that we need to better understand the findings and how they may translate to humans before we treat additional patients. This may delay our pulmonary program a bit, but it’s just part of drug development. As the long-term toxicology data come in, we will work as quickly as we can to understand their implications for ARO-ENaC and the patients we hope to serve. We remain committed to the pulmonary platform and are moving ahead aggressively with our other pulmonary programs, two of which have already been nominated as clinical candidates.”

AROENaC1001 (NCT04375514) is a Phase 1/2 dose-escalating study to evaluate the safety, tolerability, and pharmacokinetic effects of investigational ARO-ENaC in normal healthy volunteers and to evaluate the safety, tolerability, and efficacy in patients with CF.

About Arrowhead Pharmaceuticals

Arrowhead Pharmaceuticals develops medicines that treat intractable diseases by silencing the genes that cause them. Using a broad portfolio of RNA chemistries and efficient modes of delivery, Arrowhead therapies trigger the RNA interference mechanism to induce rapid, deep, and durable knockdown of target genes. RNA interference, or RNAi, is a mechanism present in living cells that inhibits the expression of a specific gene, thereby affecting the production of a specific protein. Arrowhead’s RNAi-based therapeutics leverage this natural pathway of gene silencing.

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