Zombie biotech Sesen Bio's resurrection plans limping again as FDA rejects bladder cancer drug

The stroke of 4 p.m. on a Friday is witching hour for biotechs, and it proved to be a scary night for Sesen Bio.

The once zombie, now resurrected biotech was hoping for an approval for bladder cancer asset Vicineum (oportuzumab monatox-qqrs), but data and manufacturing issues have scuppered those plans.

The FDA handed down a complete response letter for the next-generation antibody-drug conjugate, which is being developed as an alternative to losing the bladder.

Sesen had submitted its med for BCG-unresponsive non-muscle invasive bladder cancer (NMIBC), a condition that primarily affects men and is typically treated with surgery. But this isn't always effective; about 60% of patients diagnosed with NMIBC will also undergo BCG immunotherapy.

Vicineum comprises a recombinant fusion protein that targets epithelial cell adhesion molecule (EpCAM) antigens to deliver Pseudomonas exotoxin A. EpCAM is overexpressed in NMIBC but not in healthy bladder cells, the company says, so Sesen thinks zeroing in on it will decrease toxic effects in healthy tissues.

RELATED: New year, new name, new bladder cancer data for Sesen Bio

Sesen was hoping to get in on this target and open up a corner in the market, but it will have to wait: The FDA told the Cambridge, Massachusetts-based company that the application for Vicineum cannot be approved as submitted. The agency provided recommendations on additional clinical/statistical data and analyses that will be needed as well as flagged chemistry, manufacturing and control issues related to a recent preapproval inspection and product quality.

In a short statement, Sesen said it is planning a talk with the FDA about the drug “as soon as possible” in order to discuss the next steps that are needed for an approval. No timeline was provided for this discussion nor when a resubmission might be possible.

“We are deeply disappointed by this unexpected result, and it is an unfortunate day for patients suffering from BCG-unresponsive NMIBC,” said Thomas Cannell, president and chief of Sesen.

“We remain dedicated to our mission to save and improve the lives of patients by bringing new treatment options to patients, and we intend to work closely with the FDA to understand next steps.”

Formed in 2007 by Third Rock and Flagship, Eleven Biotherapeutics built on a foundation of several discovery-stage programs by drawing in private and public money to take an IL-1 receptor inhibitor EBI-005 (isunakinra) into the clinic.

After a promising start, the plan unraveled in 2015 and 2016 when two phase 3 trial flops in dry eye disease and allergic conjunctivitis consigned the candidate to the trash. That pretty much left Eleven as a "zombie" biotech, with a preclinical-stage IL-6-targeting antibody for diabetic macular edema (EBI-031) as its lead program, a limited pot of cash to bring it forward and a share price in the penny-stock range.

Cue massive job cuts and a quick marriage with privately held Viventia later in 2016—which was essentially a takeover by the Canadian biotech, even though the combined company retained the Eleven name. The "new" biotech refocused on oncology, but then rebranded as Sesen Bio in 2018. It appears the new name isn’t bringing any better luck.

Shares in the company fell 57% after-hours on Friday. As the markets opened Monday, the stock was trading down 36% at $1.34, compared to the previous close of $2.11.