Switzerland’s Roche has pulled its anti-HIV drug Viracept off the market in Europe due to the discovery of “chemical impurity” found in some batches of the treatment, amid fears that the contamination could cause cancer.

The firm is recalling the antiretroviral in Europe “and some other world regions” after it received “several reports that some batches of Viracept (nelfinavir) 250mg tablets have a strange odour”. An analysis of the affected tablets showed they contain higher than normal levels of methane sulfonic acid ethylester, a known genotoxic substance which is harmful to DNA and can lead to cancer. Roche also stressed that the recall does not affect the USA (where Viracept is marketed by Pfizer), Canada or Japan (where it is sold by Japan Tobacco) but a company spokeswoman told PharmaTimes World News that the recall is pretty much global, excluding those territories.

Roche, in co-operation with the European Medicines Agency and national bodies, including the UK’s Medicines and Healthcare products Regulatory Agency, issued a health alert noting that as the contamination may have affected “all strengths and presentations of Viracept”, the company is performing a complete recall and patients must contact their doctor immediately as they will have to change to another appropriate protease inhibitor. However, the EMEA said that “the level of risk to patients resulting from this contamination is difficult to measure, and is currently under further evaluation”.

No foul play is suspected and the problem seems to have been due to a human error made at one of Roche’s manufacturing plants. The spokeswoman occurred at a plant in Switzerland, but was detected in Spain where batches of the drug were released for distribution around Europe and William Burns, the head of Roche’s pharmaceutical division, said that two chemicals used in the production process had caused a “low-level impurity here which we believe is unacceptable to be in our product”. He added that the firm is talking about “low parts per million, we are talking in extraordinarily small quantities.”

Roche also said the financial impact of recalling Viracept, which recorded sales of 164 million Swiss Francs (around $135 million) in 2006, will be negligible and the company has been selling the drug to low-income countries, many of them in Africa, at a rebate of roughly 30% in 2004.

The effect on patients in the UK is likely to be minimal. Viracept was introduced into the UK in 1998 and Roger Pebody, treatment adviser from Terrence Higgins Trust, the leading AIDS charity in Europe, said that many of the anti-HIV drugs which have been developed since then are more effective so “for that reason, the numbers of people using this drug are probably relatively small”, with some estimates putting the figure at less than 600.

He added that “we don’t have many details about the contamination, and how quickly Roche have reacted to it. We hope that Roche are putting all the necessary effort into creating an uncontaminated supply of the drug as fast as possible.”

Phase III Actemera data impresses again

On a positive note, Roche said its rheumatoid arthritis drug Actemra (tocilizumab) has successfully reached its goal in a multinational phase III study, with patients achieving a 'significant improvement' in symptoms.

The firm said a greater proportion of patients treated with Actemra in combination with traditional disease modifying drugs (DMARDS) achieved a significant improvement after 24 weeks, compared to those treated with DMARDS alone. A total of 1,216 patients with moderate to severe rheumatoid arthritis participated in the Phase III study, which is the second in a programme of five clinical trials currently running on Actemra.

In January, Roche reported that Actemra was more effective than methorexate according to data from its first Phase III trial of the drug outside Japan. Actemra was launched in June 2005 in the latter country as a therapy for Castleman's disease and in April 2006 it was filed there for the additional indications of rheumatoid arthritis and systemic-onset juvenile idiopathic arthritis.