Sivextro

Drug Overview

Sivextro is a second-generation oxazolidinone, while tedizolid phosphate is a prodrug that is cleaved in the bloodstream to the active antibiotic tedizolid. The active moiety tedizolid inhibits bacterial protein synthesis by interacting with the bacterial 23S ribosome initiation complex. The drug has activity against a broad spectrum of bacterial strains, mainly Gram-positive strains including MRSA. It has also exhibited activity against some Gram-negative bacterial strains, including bacterium Legionella and the bacterium Chlamydia. Sivextro has demonstrated enhanced in vitro potency against most Gram-positive strains, ranging from four to 16 times that of the first-generation oxazolidinone Zyvox. The drug has also demonstrated potency against Zyvox-resistant strains.

Analyst Outlook

Sivextro (tedizolid phosphate; Cubist Pharmaceuticals/Bayer/Dong-A Pharmaceutical) is a second-generation oxazolidinone antibacterial. In June 2014, the US Food and Drug Administration (FDA) approved the drug for the treatment of acute bacterial skin and skin structure infections (ABSSSI), including cases associated with the clinically significant methicillin-resistant Staphylococcus aureus (MRSA). Sivextro demonstrated significantly higher in vitro potency than Pfizer’s first-to-market oxazolidinone, Zyvox (linezolid). Phase III development has also indicated non-inferiority of oral or intravenous Sivextro to Zyvox in ABSSSI. Datamonitor Healthcare believes that Cubist should emphasize Sivextro’s clinical superiority in the treatment of ABSSSI, as this differentiation will be critical in enhancing the drug’s uptake in this market. It will also enable the company to moderate the intense commercial competition anticipated from Zyvox, and subsequently from generic linezolid in the skin infections market.