Takeda ups bet on Mersana's armed antibodies to $1B-plus, snags lead drug rights

Whatever Takeda learned about Cambridge, MA-based Mersana Therapeutics over the course of its two-year collaboration, the experience left them eager for much, much more. The biotech announced today that the Japanese pharma company snagged ex-U.S. commercial rights to its lead preclinical antibody drug conjugate while expanding the realm of their partnership to include a range of new targets.

The key to the deal is XMT-1522, an armed antibody program now just months from the clinic. While antibody drug conjugates are nothing new in the biotech world, Mersana has been building a reputation for original technology that promises to create ADCs that fairly bristle with anticancer warheads, and XMT-1522 is the prototype.

Takeda is paying $40 million in the upfront, adding $20 million as a bonus for an IND expected to clear soon, another $20 million in upcoming equity investments and a further $750 million in potential milestones. Added with Takeda's two earlier collaborations, says Mersana CEO Anna Protopapas, and Takeda is on board for a package of deals that now easily surpasses $1 billion.

In exchange, Takeda gets ex-U.S. and Canadian rights to a HER-2 targeting cancer drug.

What's the attraction?

Mersana's drug uses a unique linker technology to connect an antibody--developed by Tillman Gerngross's antibody engineering shop Adimab in New Hampshire--with up to 15 drugs. Current ADC tech, says Mersana CEO Anna Protopapas, is typically limited to three or four drugs in the payload. And Mersana has added proprietary treatments to the mix.

That added firepower should make this drug more efficacious than the drugs currently on the market, says Protopapas, while greatly expanding its range.

"We are efficacious in tumors that express HER-2, but at very low levels," says the CEO, which gives this drug the potential to treat a much larger patient population. Investigators say the treatment has promise for breast, gastric and non-small cell lung cancers.

For Protopapas, the deal also means continued work with some old, and new, colleagues at Millennium, the cancer company she recently helmed for Takeda as it went through a top-to-bottom reorganization. It's also a chance to continue to build a biotech that now has 44 staffers, with plans for new hiring as well.

This year marks a major transition point for the biotech. Mersana is moving from a research company to a development company, with its first drug headed into the clinic. Another program, still under wraps, is slated to enter the clinic next year, with a third being readied for 2018. And it's hanging on to U.S. commercialization rights to the lead drug.

In the meantime, Mersana has raised $62 million in venture capital and has another collaboration with Merck Serono that takes their total amount of biobucks on the table to more than $2 billion.

"As the pipeline evolves, a partner like Takeda and partnerships like this allow us to accelerate moving these programs forward," says Protopapas. "They have resources that complement ours, they know antibody drug conjugates and oncology and they're very excited about the platform."

- here's the release

Special Reports: FierceBiotech's 2012 Fierce 15 - Mersana Therapeutics | FierceBiotech's 2011 Women in Biotech - Anna Protopapas