AstraZeneca, GlaxoSmithKline stake rival claims on new lupus therapies

AstraZeneca says it has a prime late-stage drug contender in the clinic that has the potential to compete for the lupus market. But it is lining up against GlaxoSmithKline, which has been touting promising Phase III data this week for a new subcutaneous formulation of Benlysta, a drug that has frequently disappointed analysts who have been tracking its sales over the years.

Investigators for AstraZeneca ($AZN) say that an IV version of anifrolumab (MEDI-546) hit its marks in a Phase II study, with the antibody directed against the type I interferon (IFN) receptor, cutting key disease activity measures while reducing the need for corticosteroids in controlling the disease.

Based on the SRI4 responder index after 169 days of therapy, 34.4% of patients receiving anifrolumab 300 mg IV achieved SRI4 along with 28.8% of patients receiving anifrolumab 1,000 mg IV every four weeks. Only 17.6% of patients receiving placebo responded similarly.

The trial also met both secondary efficacy endpoints after a full year with a higher rate of response: 51.5% of the 300-mg group achieved SRI4 compared to about half that percentage for the placebo arm.

AstraZeneca CEO Pascal Soriot

AstraZeneca has already begun its Phase III program for the drug, which was singled out as a top blockbuster prospect when the pharma giant was fighting off an unwelcome megamerger offer from Pfizer ($PFE). AstraZeneca CEO Pascal Soriot estimated that a combination of anifrolumab and another drug, sifalimumab, could achieve $1 billion in annual revenue, compared to analysts' estimates ranging from $200 million to $1 billion.

Sifalimumab, though, didn't make the cut for Phase III.

"While the sifalimumab data were encouraging, we believe anifrolumab has a more favorable benefit-risk profile and therefore we do not intend to develop sifalimumab in SLE," a spokesperson for AstraZeneca tells FierceBiotech. "This is consistent with our approach of following the science."

Sales estimates for lupus have been problematic. GlaxoSmithKline ($GSK) has been working to build sales of IV-delivered Benlysta, which have disappointed analysts after it warranted the first new drug approval in the field in more than 50 years. In the first 9 months of this year, GSK reported $251 million in sales, according to a report from PMLiVE.

GSK is hoping that it can do better with a subcutaneous version of the drug. 

After 52 weeks of dosing in Phase III, investigators reported that 60.8% demonstrated reduced disease activity compared to placebo--but not by a wide margin. The placebo plus standard-of-care arm (glucocorticosteroids and immunosuppressants) response at 52 weeks was 48.47%.

That's good enough to seek regulatory approval now, says GSK, which has been making steady, though largely marginal, gains in the clinic in recent years.

- here's the release from AstraZeneca
- here's the release from GSK

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