NEW YORK (TheStreet) -- Shares of Ionis Pharmaceuticals (IONS) - Get Report are plummeting by 31.96% to $23.99 on heavy trading volume Thursday morning, after the company's partner GlaxoSmithKline (GSK) decided against initiating a phase-three study for Ionis-TTR, which the companies have been co-developing.

The FDA in April placed a clinical hold on GlaxoSmithKline's phase-three study of Ionis-TTR as a potential treatment for patients with transthyretin amyloid cardiomyopathy, a potentially fatal organ condition in which the misfolded transthyretin protein accumulates in the cardiac muscle.

GlaxoSmithKline will evaluate other options for transthyretin amyloid cardiomyopathy after additional data are available from studies currently under way, according to a statement by Ionis.

Ionis's own late-stage study of the treatment in patients with a hereditary version of transthyretin amyloidosis remains on track, and clinical data are expected in the first half of 2017.

Additionally, JPMorgan (JPM) issued a report about a potential setback with Ionis's experimental drug for the hereditary version of transthyretin amyloidosis, known as familial amyloid polyneuropathy, Bloomberg reports.

A few patients, less than five, have developed significant drops in platelet levels after taking the medication, JPMorgan claimed.

About 9.75 million shares of Ionis have been traded so far today, well above the company's average trading volume of roughly 1.38 million shares per day. 

Separately, TheStreet Ratings team rates the stock as a "sell" with a ratings score of D.

Ionis's weaknesses include its feeble growth in its earnings per share, deteriorating net income, disappointing return on equity, weak operating cash flow and generally high debt management risk.

You can view the full analysis from the report here: IONS

TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this article's author. 

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