Japanese drugmaker Chugai – a unit of Swiss drug giant Roche – saw its stock take a hit yesterday following news of a potential link between its much hailed rheumatoid arthritis drug Actemra and 15 patient deaths.

The company said 4,915 patients were treated with Actemra (tocilizumab) between April 2008 and February 2009, out of which 15 deaths could possibly be linked to the drug. However, Chugai stressed that while it could not rule out a “causal relationship”, the majority (13 of 15) of fatalities occurred in patients aged 60 and over following conditions such as heart failure and heart attacks, making it difficult to determine whether the drug played a significant role or not.

The news has obviously disappointed shareholders, adding fuel to fears that the drug - which also suffered a recent setback in the all-important US market - will fail to attain its predicted blockbuster status after all. Analysts had predicted that Actemra, a novel interleukin-6 (IL-6) receptor-inhibiting monoclonal antibody, could generate sales of $2-$4 billion as it offers a new option for patients who do not respond to anti-tumour necrosis factor-alpha therapies such as Abbott Laboratories’ Humira (adalimumab), Johnson & Johnson/Schering-Plough’s Remicade (infliximab) and Wyeth/Amgen’s Enbrel (etanercept).

Analyst views on the potential impact of the news on the drug’s future are mixed, according to media reports. Merrill Lynch analyst Ritsuo Watanabe was quoted as saying that although the data might be viewed as “negative news at first glance” he believes it “will not affect significantly the potential of the drug”. On the other side of the fence, Deutsche Bank's Kenji Masuzoe expressed concern that healthcare professionals and patients may “hesitate to use Actemra and decide to switch to alternatives”, which could significantly dent sales.

Actemra first received clearance in Japan for rheumatoid arthritis back in 2006, and won approval in Europe earlier this year. But the drug’s entry onto the US market was subjected to a delay last December after US regulators requested a Risk Evaluation and Mitigation Strategy plan to help ensure that doctors prescribe and administer the therapy correctly, as well as non-clinical animal data in addition to what was submitted in the original Biologics License Application.