Pfizer's report of a new serious adverse event with PF-06939926, its gene therapy for Duchenne muscular dystrophy, saw an immediate beneficiary emerge, in the shape of Sarepta, whose shares rose 11% on Friday. In total three serious events have occurred in the phase Ib trial, two of which were said to be due to complement activation; patients had to be treated with Alexion’s complement inhibitor Soliris. Even without the toxicity concerns PF-06939926 does not appear to be as effective as Sarepta’s own SRP-9001 gene therapy, although data on both come only from small numbers of patients. At one year Pfizer’s project showed a 3.5-point improvement from baseline in NSAA total score, a measure of muscle function, in six patients. SRP-9001 has previously shown a 6.5-point improvement from baseline at nine months in four patients. The safety of SRP-9001 also looks cleaner: one case of rhabdomyolysis, a breakdown of skeletal muscle, has been reported so far. With phase III studies due to start soon for both projects, safety will be a key factor to watch.
|Forecasts for selected DMD gene therapies|
|Project||Vector type||Company||2026e sales ($m)||Notes|
|SRP-9001||AAVrh74||Sarepta||3,192||One case of rhabdomyolysis in phase II study 102, expression and functional data expected Q1 2021; phase III study 301 to start H2 2020|
|SGT-001||AAV9||Solid||431||Phase I/II Ignite DMD trial has had three clinical holds; the last, in Nov 2019, was due to a patient suffering serious side-effects including complement activation|
|PF-06939926||AAV9||Pfizer||-||Phase Ib study had three serious adverse events, two likely due to complement activation (NCT03362502); phase III to start H2 2020 in 99 patients, primary endpoint change from baseline in NSAA at 52wk (NCT04281485)|
|Source: EvaluatePharma & company releases.|