Kiniksa reports positive results for rilonacept in Phase III pericarditis trial

Shares in Kiniksa Pharmaceuticals gained as much as 31% on Monday after the company said the Phase III RHAPSODY trial showed that rilonacept achieved its primary and all major secondary efficacy endpoints in patients with recurrent pericarditis. The company expects to submit an FDA filing for rilonacept later this year, with CEO Sanj Patel saying "we believe rilonacept has the potential to be the first FDA-approved therapy for recurrent pericarditis."

Rilonacept was developed by Regeneron Pharmaceuticals, which markets the drug in the US under the name Arcalyst for the treatment of cryopyrin-associated periodic syndromes (CAPS). Kiniksa said it licensed rilonacept from Regeneron in 2017 for evaluation in diseases believed to be mediated by both IL-1-alpha and IL-1-beta, including recurrent pericarditis.

The RHAPSODY trial recruited 86 patients aged 12 years an older with a diagnosis of recurrent pericarditis. The primary analysis population included 61 actively symptomatic patients who were failing standard of care treatment, including nonsteroidal anti-inflammatory drugs, colchicine or corticosteroids. They initiated rilonacept treatment during a run-in period, discontinued background medications, and achieved and maintained clinical response on rilonacept monotherapy, the company said. Clinical responders were then randomised to receive once weekly subcutaneous injections of rilonacept or placebo, with the primary outcome measure assessing time to first pericarditis recurrence at 24 weeks.

Pericarditis recurrences low

According to Kiniksa, the median time to pericarditis recurrence in the randomised withdrawal period could not be estimated in the rilonacept group "due to the low number of recurrences" in this treatment arm, while the median time-to-recurrence for placebo recipients was 8.6 weeks.

In terms of secondary goals, Kiniksa reported that 81% of rilonacept recipients maintained clinical response at the 16-week mark of the randomised withdrawal period, compared to 20% for placebo. The company said "consistent results were observed at week eight and week 24 and were also highly statistically significant." It added that the proportion of patients with absent or minimal pericarditis symptoms at week 16 was 81% and 25% for rilonacept and placebo, respectively.

'Transformational therapeutic'

"In fact, rilonacept patients experienced no or minimal pericarditis pain for nearly 95% of study days through week 16, compared to less than half of study days for placebo recipients, which was highly statistically significant," noted chief medical officer John Paolini. He suggested by treating and preventing disease recurrence, rilonacept could turn out to be "a transformational therapeutic advancement in the treatment of patients with recurrent pericarditis and…become the first FDA-approved therapy for this debilitating autoinflammatory disease."

Meanwhile, Kiniksa said rilonacept was well-tolerated in the RHAPSODY study, with adverse events consistent with the drug's FDA-approved CAPS label. Additional analyses of the trial are ongoing, and Kiniksa plans to present the data at a future medical meeting or in a publication.

The drug was previously granted breakthrough therapy status for pericarditis by the FDA. Based on the RHAPSODY data, the biologic license application for CAPS will transfer to Kiniksa. The company noted that upon FDA approval of the drug in the pericarditis indication, it would assume the sales and distribution of rilonacept for the approved indications in the US, and evenly split profits on sales with Regeneron.

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