Epizyme slides on Phase I data for EPZ-5676

Epizyme Inc. (NASDAQ:EPZM) fell $11.77 (37%) to $19.94 on Thursday after reporting data from 16 patients in the first four cohorts of an open-label Phase I trial of EPZ-5676 to treat adults with heavily pre-treated advanced hematological malignancies -- the first human data from the company. Epizyme said treatment effects "consistent with the genetically defined therapeutic mechanism of action" of EPZ-5676 were observed in four of eight acute leukemia patients with a rearrangement of the myeloid-lymphoid or mixed-lineage leukemia (MLL; HRX) gene. No treatment effects were observed in patients without MLL rearrangement. The maximum tolerated dose has not yet been reached.

Analysts said the data are too early and patient number too small to draw conclusions, but they expressed concern about EPZ-5676's lack of effect in the four of eight patients with the MLL rearrangement. Analysts also said the "dose and regimen are far from optimized." One analyst also attributed the selloff to Epizyme being overvalued prior to the data release; the company raised $88.7 million through the sale of shares at $15 in an IPO in 1H13. Before Thursday's slide, Epizyme was valued at $901.2 million. ...