Selecta slumps as interim gout data gets frosty reception

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Management talked up the fact that the serum uric acid levels of 75% of participants were below 6 mg/dl after three months. (bfishadow/CC BY 2.0)

Selecta Biosciences has posted three-month data on SEL-212 in chronic severe gout. The biotech painted data from the ongoing phase 2 trial as positive for the prospects of SEL-212, but the outside world took a different view, sending Selecta’s stock down by more than 20% premarket.

Watertown, Massachusetts-based Selecta designed SEL-212 to be a non-immunogenic version of uricase capable of clearing uric acid deposits from the body. The drug features a combination of SVP-Rapamycin and pegsiticase designed to induce the creation of regulatory T cells that stop antidrug antibodies from forming, thereby protecting the therapeutic enzyme and enabling sustained reductions in uric acid.

Selecta thinks interim data from the phase 2 trial support its hypothesis. Management talked up the fact that the serum uric acid levels of 75% of participants were below 6 mg/dl after three months and compared the dosing schedule and gout flare rate favorably to Krystexxa.

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Krystexxa, now owned by Horizon Pharma, is a pegloticase drug that won FDA approval at the start of the decade on the strength of data showing it brought the uric acid levels of 38% to 47% of patients down below 6 mg/dl during the first six months of treatment. The rate of gout flare, a painful event, in the first few months of the Krystexxa trials was 74%. The one-month rate for SEL-212 was 25%.

The significance of the comparisons to Krystexxa is questionable given the small number of evaluable patients in the phase 2 SEL-212 trial and the usual caveats about cross-study comparisons. 

Investors took against the data. Selecta’s stock price fell more than 20% in premarket trading, before improving somewhat once the financial day got properly underway. The stock is down 10% at the time of writing.

Selecta thinks the drug has a future, though, and is already making plans for phase 3. That trial will give six monthly injections of SEL-212 and assess the proportion of patients with serum uric acid levels below 6 mg/dl at three and six months.