Despite setbacks in the USA, Novartis’ Aclasta could yet be strong challenger to other bisphosphonate drugs in the treatment of both osteoporosis and Paget’s disease.

This was the message of two studies presented at the Sixth European Congress on Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ECCEO) late last week in Vienna.

In two-year follow-up of a randomised study published in 2005, only three of 152 Paget’s disease patients who had received a single intravenous (IV) dose of Aclasta (zoledronic acid) lost biochemical remission compared to 49 of 115 patients given a daily oral dose of Procter & Gamble/Sanofi-Aventis’ Actonel (risedronate).

Paget’s disease is a chronic disorder of the skeleton, which affects about 5% of the European population. Oral bisphosphonates are currently the first-line treatment but, to date, none of these drugs has been able to achieve remission, even when used in high doses.

The second study demonstrated that a single infusion of zoledronic acid produced more rapid and greater reductions in markers of bone resorption than 24 weeks’ treatment with Merck & Co’s once-weekly oral Fosamax (alendronate). While fracture outcomes will be essential for approval in an osteoporosis indication, these results are potentially very important, since markers of bone turnover are useful surrogate indicators of fracture risk.

A once-yearly infused bisphosphonate could revolutionise the osteoporosis market. However, the US Food and Drug Administration (FDA)’s request for more data in Paget’s disease and the existence of orally-dosed bisphosphonates means that regulatory authorities are likely to be ultra-cautious in demanding hard evidence of Aclasta’s long-term safety before granting an osteoporosis market.

From Sue Lyon at ECCEO in Vienna