Shares of Ionis Pharmaceuticals (IONS) - Get Report plummeted this morning after the company announced that its partner GlaxoSmithKline (GSK) - Get Report had decided not to initiate a Phase 3 outcome study that was planned to evaluate IONIS-TTRRx in patients with transthyretin amyloid cardiomyopathy, or TTR amyloid. Yesterday, JPMorgan analysts had said they believe Alnylam's (ALNY) - Get Report TTR program has an edge in safety over Ionis' TTRRx. In early April, Ionis disclosed that the FDA had put a clinical hold on the CARDIO-TTR study, delaying the start of the phase 3 cardiomyopathy trial for its TTRRx.

CLINICAL HOLD: Before the market open on April 7, Ionis disclosed that CARDIO-TTR, a phase 3 study planned by GlaxoSmithKline to evaluate the IONIS-TTRrx program in patients with TTR amyloid, had been put on clinical hold by the FDA as a result of safety findings in the ongoing Ionis' NEURO-TTR study and as GlaxoSmithKline provided answers to questions about the protocol for the study. During the company's first quarter earnings call, Ionis confirmed that low levels of platelets were observed in "less than a handful" of patients in the TTRRx program.

JP MORGAN PREFERS RIVAL: Yesterday, JPMorgan analysts Jessica Fye and Anupam Rama said that the disclosure that a small number of patients in the IONIS-TTRRx phase 3 study had experienced platelet drops below 50 K/mm3 raises questions around what this could mean for Ionis, but also for Alnylam, which is working on treatments in the same area. The analysts view this as a "clear risk" for Ionis to monitor in its TTRRx program, and a side effect that will have to be weighed in the context of the overall risk/benefit profile. However, the evidence is not sufficient to call this a "platform problem" for the company's other products, they noted. Fye and Rama pointed out that they believe Alnylam has the edge on safety profile for its patisiran and revusiran versus Ionis' TTRRx. Importantly, thrombocytopenia has not emerged as a safety concern in any of Alnylam's ongoing programs, they noted. JP Morgan has an Overweight rating and $80 price target on Alnylam's shares and a Neutral rating and $53 price target on Ionis' shares.

OUTCOME STUDY HALTED: Ionis, which is currently evaluating IONIS-TTRRx in an ongoing Phase 3 study, NEURO-TTR, in patients with transthyretin familial amyloid polyneuropathy, said this morning that partner GlaxoSmithKline has decided not to initiate a Phase 3 outcome study, CARDIO-TTR, which was planned to evaluate IONIS-TTRRx in patients with TTR amyloid cardiomyopathy. Helen Merianos, Medicine Development Leader for GlaxoSmithKline's TTR amyloidosis program, said: "GSK remains committed to developing innovative medicines for the treatment of amyloidosis and to our ongoing collaboration with Ionis to develop IONIS-TTRRx for TTR amyloidosis. We will assess the results from the NEURO-TTR study to inform our next steps for TTR amyloid cardiomyopathy."

PRICE ACTION: In morning trading, shares of Ionis had dropped 32% to $23.81, while GlaxoSmithKline's stock was fractionally down to $43.10 per share. Alnylam's shares had gained almost 11% to $70.51 following the news from its rival.

Reporting by Jessica de Sa-Mota.

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