(Updated with more details)

BOSTON (

TheStreet

) --

ImmunoGen

(IMGN) - Get Report

just disclosed partial results from the pivotal study of T-DM1 in third-line breast cancer patients that's to be presented at a medical meeting on Saturday.

The objective response rate in the study was 32.7%, assessed by independent review, for the 110 breast cancer patients enrolled in the study.

These results are better than the earlier, similar

phase II study of T-DM1

in which 25% of patients responded. A subset of patients in this earlier study with confirmed Her-2 positive status had a 32% response rate to T-DM1.

ImmunoGen made the disclosure today in an 8-k filing with the

Securities and Exchange Commission

. No other details from the study were provided.

Roche/Genentech

, which owns the rights to T-DM1, conducted the study. The company said it plans to seek regulatory approval for T-DM1 if the results from the study were positive.

T-DM1 is a second-generation version of Roche/Genentech's blockbuster breast cancer drug Herceptin. It consists of Herceptin (also known as trastuzumab) linked to a tumor-killing chemotherapy payload developed by ImmunoGen.

-- Reported by Adam Feuerstein in Boston

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