# Sesen Bio

Source: https://onco.cc/companies/sesen-bio/  
OnCo record `sesen-bio` (Company). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Sesen Bio developed Vicineum, a targeted protein treatment put directly into the bladder for early bladder cancer that had stopped responding to BCG. The US regulator turned down its application in 2021, and in 2023 the company merged into Carisma Therapeutics.

## Summary

Sesen Bio developed targeted fusion protein therapeutics for cancer. Its lead candidate, Vicineum (VB4-845), is a locally administered fusion protein joining an anti-EpCAM antibody fragment to a truncated Pseudomonas exotoxin A, for non-muscle invasive bladder cancer. The single-arm Phase 3 VISTA trial in BCG-unresponsive NMIBC (NCT02449239) enrolled 133 patients; the FDA accepted the Biologics Licence Application with Priority Review and issued a Complete Response Letter on 13 August 2021, and in July 2022 the company paused further US development of Vicineum (company 10-K for 2022). Sesen Bio and Carisma Therapeutics closed their merger on 7 March 2023; the combined company took the Carisma name and ticker CARM, and Sesen Bio holders received a contingent value right tied to any sale of legacy assets including Vicineum. The company was formerly called Eleven Biotherapeutics (SEC records).

## Fields

- Kind: Company
- Last checked: 2026-11-04
- Also known as: Sesen Bio, Inc.; Eleven Biotherapeutics, Inc.
- HQ: Cambridge, MA
- Type: biotech

## Notes

- Carisma Therapeutics is not a company record in OnCo, so acquiredBy is not set; this was a merger in which Carisma's business continued under Sesen Bio's listed entity.
- None of Sesen Bio's ClinicalTrials.gov studies (NCT02449239, NCT00462488, NCT00272181, NCT00412776, NCT00481936) is a trial record in OnCo yet.
- Vicineum (VB4-845, also written Vicinium) is not a drug record in OnCo.
- Founding year not stated (2010 is Third Rock's year of investment).

## Sources

- Sesen Bio annual report 2022 (SEC 10-K): https://www.sec.gov/Archives/edgar/data/1485003/000148500323000090/sesn-20221231.htm
- Carisma closes merger with Sesen Bio (SEC exhibit, 7 March 2023): https://www.sec.gov/Archives/edgar/data/1485003/000110465923029687/tm238578d1_ex99-1.htm
- Third Rock Ventures portfolio entry: https://www.thirdrockventures.com/portfolio/sesen

## Connected records

- cancers: [Non-muscle-invasive bladder cancer](https://onco.cc/cancers/non-muscle-invasive-bladder-cancer/)
- fronts: [Targeted Therapy](https://onco.cc/fronts/targeted-therapy/)
- targets: [EpCAM](https://onco.cc/targets/epcam/)
- companies: [Third Rock Ventures](https://onco.cc/companies/third-rock-ventures/)

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