Schering AG has suffered a potential major setback after it received an approvable letter from the US Food and Drug Administration for its anti-cancer agent, Bonefos (clodronate). A dearth of information from the German company on what it must do in order to win final approval led to a 6% drop in the firm’s share price as investors grew concerned that additional trials could be requested.

Marc Rubin, a member of Schering’s board of executive directors, limited himself to saying: “We look forward to the opportunity to meet with the FDA so we can advance the approval process”.

Investors had expected the application to be approved outright after Bonefos received fast-track designation from the FDA in September for reducing bone metastases in late-stage breast cancer patients [[09/09/04b]]. The drug has been available outside the US for some time to treat tumour-related bone damage and high calcium in the blood – a consequence of cancer – and this new indication had caused considerable excitement among analysts. Estimates of potential sales for Bonefos if the new indication gets US approval vary from 200 to 700 million euros, compared with just 49 million euros in 2003. Newer drugs in Bonefos’ class such as Novartis’ Zometa (zoledronic acid), and Roche’s Bondronat (ibandronic acid) are selling well, but are injectible, hence the potential market for Schering’s oral drug.

This delay is therefore a disappointment for Schering but could become a really serious problem if the FDA requires more clinical data – a process that could take a couple of years. Indeed, Schering’s US affiliate, Berlex, has had other problems with the FDA of late – in September, the agency requested more manufacturing data to approve hormone-replacement therapy Angeliq (estradiol with drospirenone) [[16/09/04c]], and in November issued only an approvable letter for Yaz (ethinyl estradiol and drospirenone) – a new low-dose form of the highly successful Yasmin contraceptive [[22/11/04e]].