Ionis Pharmaceuticals, Inc.’s IONS shares plunged 11% after the company announced that the FDA has placed a clinical hold on the phase III CARDIO-TTR study on IONIS-TTRRx. The study, which is being conducted by GlaxoSmithKline plc GSK, will evaluate IONIS-TTRRx in patients suffering from transthyretin (TTR) amyloid cardiomyopathy. Ionis mentioned that Glaxo is in the process of finalizing the protocol for the CARDIO-TTR study. However, in that process, the FDA put the study on clinical hold while Glaxo provides answers to the regulatory agency’s questions about the protocol arising from Ionis' ongoing NEURO-TTR study. The NEURO-TTR study is a phase III study currently underway in patients with TTR familial amyloid polyneuropathy. Ionis said that the NEURO-TTR study is regulated by a separate division at the FDA and is continuing as planned. It should be completed in the first half of 2017. We note that IONIS-TTRRx is being developed by Ionis in collaboration with Glaxo for all forms of TTR amyloidosis. Per the terms of the agreement, Glaxo has an option to exclusively license the IONIS-TTRRx program. Considering that Kynamro is Ionis’ only approved product, the clinical hold on the CARDIO-TTR study is disappointing. Per information provided by Ionis in its press release, TTR amyloidosis is a severe, progressive and fatal disease with multiple overlapping clinical manifestations. There is strong unmet need for drugs targeting this disease. Taking into account the eligible patient population, successful development and subsequent commercialization of IONIS-TTRRx would be a huge boost for the company. Apart from IONIS-TTRRx, the company has nusinersen (spinal muscular atrophy in infants and children – phase III) and volanesorsen (familial chylomicronemia syndrome and familial partial lipodystrophy – phase III) in its pipeline. Ionis has a collaboration with Biogen Inc. BIIB for nusinersen. Ionis is a Zacks Rank #3 (Hold) stock. Actelion Ltd. ALIOF is a better-ranked stock in the health care sector carrying a Zacks Rank #1 (Strong Buy). Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report GLAXOSMITHKLINE (GSK): Free Stock Analysis Report ACTELION LTD (ALIOF): Free Stock Analysis Report BIOGEN INC (BIIB): Free Stock Analysis Report IONIS PHARMACT (IONS): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research