If eventually approved, TDM-1 is expected to become a new standard of care for second-line treatment of metastatic, HER2-positive breast cancer, largely supplanting Glaxo's Tykerb, which posted 2011 sales of $372 million. ImmunoGen will receive single-digit royalties pegged to the TDM-1 sales by Genentech in the U.S. and Roche in the rest of the world. Roche continues to study TDM-1 in breast cancer patients with less advanced disease, which may help the company extend the life of its Herceptin franchise, which brought in $5 billion in sales last year. Another Roche drug, pertuzumab, is already filed with FDA, which is expected to issue an approval decision on June 8, just days after oncologists leave the ASCO meeting here. Pertuzumab, which will be sold under the brand name Perjeta, is similar to Herceptin in that it is designed for use in patients with breast cancer that contains an overexpression of HER2 receptors. Perjeta targets HER2 receptors but in a different way than Herceptin. This allows Perjeta to be used in combination with Herceptin or TDM-1. In a pivotal study, the combination of Perjeta, Herceptin and chemotherapy prolonged progression-free survival by six months compared to Herceptin and chemotherapy alone. This study enrolled women with previously untreated HER2-positive metastatic breast cancer. --Written by Adam Feuerstein in Boston. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: firstname.lastname@example.org. Follow TheStreet on Twitter and become a fan on Facebook.