Robertson, Stephens analyst Edward Hurwitz on Friday said that, based on information he gleaned from Japanese publications, Amgen Inc.'s lead in the thrombopoietin race may be tenuous.

AMGN in April became the first company in the TPO race - the others being Genentech Inc., Novo Nordisk subsidiary ZymoGenetics, and AMGN's partner Kirin - to enter the protein that stimulates platelet production into clinical trials.

However, Hurwitz said that AMGN's version of the drug is an E. coli-derived, truncated, PEGelated protein, a formulation of the drug that was faster to develop than the natural protein but that may have drawbacks. He based those conclusions on published comments by Kirin.

Awaiting data

The full implications of those changes won't be known until the first clinical data are available later this year, he noted. However, said Hurwitz, the modifications to the protein are substantial, raising the risks of development