Mersana Therapeutics: Antibody-drug conjugates

Platform: Fleximer platform for antibody-drug conjugates
Company: Mersana Therapeutics
Website: www.mersana.com
Partnerships: Endo Pharmaceuticals and Adimab (concerning antibody-drug conjugates)

Mersana Therapeutics has a unique new technology for connecting combining small molecule anti-cancer drugs and tumor-targeting antibodies in a single package. Called antibody-drug conjugates (ADCs), such compounds have generated significant interest from pharma giants and investors for their ability to hammer cancers with reduced toxicity in healthy tissues compared with anti-tumor treatments of the past.

The Cambridge, MA-based biotech has thus far proven the mettle of its ADCs in preclinical studies, but early this year that company had built enough of an offering in this hot area to land a partnership deal with Endo Pharmaceuticals ($ENDP), which has agreed to shell out up to $270 million to the biotech for ADCs against cancer. Mersana CEO Nicholas Bacopoulos, a Pfizer veteran and biotech entrepreneur, then led the startup to a $27 million venture round led by NEA and a partnership with Adimab this year.

Earlier ADC technologies have had limited success on the market, in part because of the linker chemistries that connect anti-cancer toxins with antibodies. Mersana offers a new way of building the compounds, using its polymer chains as a "backbone" to which a targeted antibody or other agent and multiple types of anti-cancer chemicals can be strongly linked--rather than linking the antibody directly to the cytotoxin, which presents solubility hurdles that Mersana's ADCs avoid, Bacopoulos explained in an interview.

The technology sprang from the lab of Mikhail "Misha" Papisov at Massachusetts General Hospital, and PureTech Ventures helped form the company about a decade ago. The emphasis on ADCs has come in recent years, as Seattle Genetics ($SGEN), maker of the empowered antibody Adcetris, Roche and ImmunoGen ($IMGN) have advanced the field.

Mersana Therapeutics: Antibody-drug conjugates
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