Pharmacia downplays Zyvox resistance

Pharmacia has responded to the publication of a letter in The Lancet(April 14), reporting on five suspected cases of vancomycin-resistant Enterococcus faecium that were also resistant to the firm's new antibiotic Zyvox (linezolid injection and tablets), by noting that the findings were not surprising. The company pointed out that the cases are "consistent with conditions that Pharmacia researchers have already reported to regulatory authorities and physicians around the globe."

In the letter, researchers from the University of Illinois in the USA describe five patients with VRE, a serious infection that has lost susceptibility to what is still considered a last-line antibiotic. Pharmacia notes that all the cases involved a raised susceptibility to developing resistant strains, including infections associated with prostheses or which could not be treated surgically due to their location. The firm also notes that two of the patients actually improved while receiving Zyvox.

Indeed, the emergence of resistance is not an unusual occurrence in antibiotic drug development, even before a new agent reaches the market. For example, cases of resistance to Synercid (quinupristin/dalfopristin), the much-touted new antibacterial from Aventis, were highlighted at scientific meetings in the build-up to its introduction in the USA. Despite this, sales of the antibiotic are ramping up, reaching 44 million euros ($39 million) in 2000, a 196% increase over the previous year (Marketletter March 12, 2001).