* Stops dacetuzumab Phase IIb DLBCL clinical trial
* Says decision based on determination that trial may fail
* To continue Phase Ib trials for NHL, multiple myeloma
* Shares fall almost 18 pct (Adds analyst's comments, details, updates share movement)
By Anand Basu
BANGALORE, Oct 5 (Reuters) - Seattle Genetics Inc (SGEN.O) stopped a mid-stage trial of its experimental cancer drug dacetuzumab based on a determination that the study was unlikely to meet its main goal, knocking its shares down about 18 percent.
The biotechnology company was developing dacetuzumab with Genentech Inc, which was acquired by Roche Holding AG (ROG.VX), to treat patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL).
DLBCL is a cancer of the B-lymphocytes and represents 30 percent of non-Hodgkin's lymphomas (NHL) in adults.
"It's definitely disappointing, but the management team has done a good job by spreading out the risk by having several products in late-stage testing," Needham & Co analyst Mark Monane said by phone.
"The good thing about Seattle Genetics is that they have number of programs going on. It's not a one trick pony."
Monane was positive on the company's late-stage trial of SGN-35 to treat relapsed or refractory Hodgkin's lymphoma and a mid-stage trial of the SGN-33 to treat acute myeloid leukemia.
The company expects to report data from the late-stage trial of SGN-35 in the second half of 2010 and from the mid-stage trial of SGN-33 in the first half of 2010.
The Phase IIb trial of dacetuzumab was discontinued based on a recommendation by the Independent Data Monitoring Committee following a pre-specified interim analysis, the company said.
"We are disappointed that the interim analysis of the phase IIb clinical trial resulted in discontinuation of the study, especially given the unmet medical need for DLBCL patients," Chief Executive Clay Siegall said.
Seattle Genetics said it will conduct a detailed analysis of data from the trial in collaboration with Genentech. Seattle Genetics said it was continuing four ongoing phase Ib trials of the drug for NHL and multiple myeloma in collaboration with Genentech.
Needham's Monane, who has a "buy" rating on Seattle Genetics' shares, said: "The management team has addressed it (dacetuzumab development) well by having a partner, Genentech, that can help guide them for next step."
Shares of Bothell, Washington-based Seattle Genetics were down 16 percent at $11.04 in early trade on Nasdaq. They earlier touched a low of $10.85.
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