A day after Micromet Inc. received a $10 million milestone payment from partner Serono SA, the companies agreed to amend their collaboration to delay for a year Micromet's option to co-promote adecatumumab, a monoclonal antibody aimed at cancer.

The companies signed the original deal two years ago, with a provision calling for Carlsbad, Calif.-based Micromet to decide whether to co-invest in the program following completion of a Phase II program. At that time, Micromet could opt to co-develop and co-promote adecatumumab (MT201) in the U.S., Europe or both, in which case it would receive a share of the profits. (See BioWorld Today, Dec. 8, 2004.)

Results from two Phase II trials - both of which missed their primary endpoints - were reported in October. Around that same time, Geneva-based Serono announced its merger with Merck KGaA, in which Merck agreed to purchase a controlling stake in the company this year, with plans to gain full ownership in the first half of 2007.

"Because of everything that's caught up in the Serono/Merck KGaA merger right now," said Chris Schnittker, senior vice president and chief financial officer of Micromet, "they're looking for an extension" on the adecatumumab deal.

"This is essentially adding one year to the program," he told BioWorld Today, during which time Micromet will continue running an ongoing Phase Ib trial to test adecatumumab in combination with docetaxel in metastatic breast cancer patients and will move to start a Phase I monotherapy study next year in patients with solid tumors.

Serono will continue funding the program, and will reimburse Micromet for costs related to the development of adecatumumab.

Overall financial terms of the potential $148 million deal remain unchanged, though Schnittker said the "revenue recognition model will change a little bit for us."

According to the 2004 agreement, Micromet received an initial license fee of $10 million, and is entitled to milestone payments of up to $138 million if adecatumumab is approved worldwide in three or more indications. So far, the antibody has been tested in breast and prostate cancers, though it might have potential in other cancers, such as lung, colon, stomach, bladder, pancreatic, head and neck, and ovarian.

Completion of the two Phase II studies resulted in a $10 million milestone payment from Serono Monday, which pushed Micromet's stock (NASDAQ:MITI) up more than 48 percent to close at $3.

The company's shares jumped another 8.3 percent on news of the collaboration amendment, gaining 25 cents Tuesday to close at $3.25.

Adecatumumab, a recombinant human monoclonal antibody of the IgG1 subclass, is designed to target the epithelial cell-adhesion molecule (EpCAM), a cell-surface protein that's often overexpressed on solid tumors. While two Phase II studies, one in metastatic breast cancer and the other in prostate cancer, failed to reach the primary endpoints, both demonstrated a positive trend.

In the breast cancer trial, adecatumumab failed to show a 25 percent clinical benefit at week 24, but data showed a significant prolongation of time to progression in patients treated with the higher dose vs. the lower dose. Progression-free survival was 336 days, 128 days and 49 days for the 10 percent, 25 percent and 50 percent (median) of patients in the high/high group compared to 112 days, 59 days and 42 days in the low/low group.

Results from the prostate cancer study demonstrated that the drug missed the endpoint of a mean change in prostate-specific antigen at week 24 over baseline, but results indicated that adecatumumab had a beneficial trend over placebo.

The next step for Micromet and Serono will be to move forward on planned or ongoing studies, as well as to explore additional clinical activities to identify the optimal dosing regimen and additional indications.

"There was some expectation that we would launch registration trials after Phase II," Schnittker said, "so [the amended collaboration] is sort of setting that new path."

Beyond adecatumumab, Micromet is developing MT103, a recombinant bispecific T-cell engager (BiTE) molecule. That product is partnered with Gaithersburg, Md.-based MedImmune Inc., which filed an investigational new drug application in August to begin a U.S. Phase I trial in non-Hodgkin's lymphoma.

Micromet is conducting a separate Phase I trial of MT103 in Germany.

Micromet, which gained a Nasdaq listing and U.S. headquarters through its merger with CancerVax Corp. earlier this year, reported a net loss of $5.8 million, or 19 cents per share, for the third quarter. As of Sept. 30, the company had cash totaling $23.1 million, which does not include the recently received $10 million milestone or any capital from a $25 million financing facility the company entered in August with Kingsbridge Capital Ltd. (See BioWorld Today, Sept. 1, 2006.)

Serono reported in September that Darmstadt, Germany-based Merck agreed to acquire the Bertarelli family's stake in the company, representing about 64.5 percent of its equity, in an all-cash deal valued at CHF16.6 billion (US$13.3 billion) and plans to pick up the remaining shares in a public tender offer next year. The combined firm will be called Merck-Serono Biopharmaceuticals. (See BioWorld Today, Sept. 22, 2006.)

Shares of Serono (NYSE:SRA) closed at $22.76 Tuesday, up 9 cents.