FDA rejects Sobi's gout drug over manufacturing concerns, leaving Amgen's Krystexxa unchallenged

Sobi's (SOBI) attempt to bring a rival to Amgen's (AMGN) blockbuster gout treatment Krystexxa to market has been delayed after the US Food and Drug Administration declined to approve the Swedish company's drug.

The FDA issued a complete response letter for NASP as a treatment for uncontrolled gout, Sobi said. The rejection postpones the launch of a product the company had projected could generate peak annual sales of between SKr4bn and SKr6bn ($410mn to $620mn).

The agency cited deficiencies at a contract manufacturing facility and requested additional data on the manufacturing control strategy for the drug's biological component, according to Sobi. The company said the FDA raised no concerns about the drug's clinical efficacy or safety profile.

Lydia Abad-Franch, Sobi's chief medical officer, said the FDA's feedback provided "a clear and actionable path forward" and that the company would work closely with the agency toward a resubmission.

NASP combines nanoencapsulated sirolimus, which prevents the formation of anti-drug antibodies, with pegadricase, a pegylated recombinant uricase enzyme that lowers serum uric acid, the primary driver of gout. In two phase 3 trials, Dissolve I and II, Sobi and its partner Selecta Biosciences reported that a higher proportion of patients receiving NASP achieved uric acid levels below the treatment target for at least 80 per cent of the sixth month of therapy, compared with those on placebo.

NASP's chief rival is Krystexxa, Amgen's every-other-week intravenous uricase infusion, which generated $1.34bn in US sales last year. Krystexxa requires weekly oral methotrexate as an immunomodulator, whereas NASP is administered monthly and could offer an alternative for patients for whom methotrexate is contraindicated, including those with severe liver or kidney disease.

Sobi has been building out its gout franchise beyond NASP. Through its acquisition of Arthrosi Therapeutics, worth up to $1.5bn, the company gained pozdeutinurad, a once-daily oral URAT1 inhibitor that reported positive topline results from one of two pivotal phase 3 trials last month. A second trial readout is expected later this year. Sobi has forecast peak sales for pozdeutinurad exceeding SKr10bn ($1.03bn), higher than its projections for NASP.