Enanta Pharmaceuticals has seen its stock more than double, despite a Phase II respiratory syncytial virus (RSV) trial failing to meet its primary endpoint.
The Phase IIb RSVHR study (NCT05568706) missed its primary endpoint, with patients treated with zelicapavir reporting no significant effect on the time to resolution of the lower respiratory tract disease (LRTD) subset of four symptoms to mild, with a difference in improvement of 0.5 days.
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The trial reported a clinically meaningful improvement in time to complete resolution of all 13 RSV symptoms was observed for zelicapavir compared to placebo, with a benefit of 2.2 days for the overall efficacy population and 6.7 days for patients with congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD), or aged 75 years or older.
Key secondary endpoints were met, including time to improvement in the Patient Global Impression of Severity (PGI-S) score, with patients who received the study drug recovering two days faster compared to those on placebo.
There were also reduced hospitalisation rates in patients who received zelicapavir and key secondary virology endpoints were met, showing a robust antiviral effect from the therapy. Zelicapavir demonstrated a favourable safety profile and was well-tolerated.
Enanta Pharmaceuticals CMO Dr Scott Rottinghaus said that the data does support Phase III development.
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By GlobalDataRottinghaus said: “These data demonstrate the potential for zelicapavir to reduce the duration of RSV symptoms in high-risk adults who face an increased risk of hospitalisation or death from this virus. We believe the totality of these data provides strong rationale for further clinical advancement of zelicapavir. Importantly, we identified multiple potential registrational endpoints for a Phase III trial.”
The trial enrolled patients who had tested positive for RSV, including those at high risk of complications – the elderly and/or those with CHF, COPD or asthma.
Enanta’s stock more than doubled on Monday, from a 29 September market open of $7.15 to a close of $15.16 – a 112.03% increase.
The once daily oral N-protein inhibitor has received Fast Track designation from the US Food and Drug Administration (FDA).
Clinical Trials Arena‘s parent company GlobalData predicts that the RSV prophylaxis market across the eight major markets (8MM: the US, France, Germany, Italy, Spain, the UK, Japan, and Australia) will grow to $6.2bn in 2030.
This will be in part due to the introduction of six pipeline products, with Sanofi’s SP-0256 set to be the top-selling product in the RSV prophylaxis market in 2030 with sales of $1.2bn, as it will be the first and only combination vaccine available for the prevention of RSV, parainfluenza, and human metapneumovirus.
Meanwhile, GlobalData predicts a sales forecast of $209m for zelicapavir in the same year.
