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Upstream Bio raises $200 million to develop treatment for severe asthma

The Waltham startup acquired the experimental antibody therapy from Japanese drug maker Astellas.

Samantha Truex is chief executive of Waltham-based Upstream Bio.Upstream Bio

Upstream Bio emerged from stealth mode Thursday with $200 million to develop an experimental drug for severe asthma that it purchased from the Japanese drug maker Astellas. The money will fuel clinical trials of the drug and allow the Waltham company to purchase an additional clinical-stage drug candidate for other immune diseases, said Upstream chief executive Samantha Truex.

The small biotech — with a workforce of about 15 people — was forged last year by a syndicate of life science venture capital firms that joined forces to bid on the Astellas drug when it was auctioned off. The investment was led by OrbiMed and the Japanese pharmaceutical firm Maruho Co.


The Astellas drug is an antibody designed to curtail a common source of inflammation and irritation in asthma: a molecule called thymic stromal lymphopoietin, or TSLP, which is released in the airways in response to allergens, infections, and smoke. When the molecule pairs with the TSLP receptor, it triggers a cascade of inflammation.

Cutting off TSLP signaling by blocking its receptor should help stop inflammation where it starts, Truex said. There are about 25 million people with asthma in the US, and Upstream estimates that around 2 million of them have a severe form of it that could potentially be treated with its drug.

The firm is emboldened by the recent success of a similar antibody therapy. Tezepelumab, sold as Tezspire by Amgen and AstraZeneca, was approved by the US Food and Drug Administration in December, based on its ability to reduce asthma attacks when taken every four weeks as an injection — not through an inhaler. That therapy targets the TSLP molecule itself, while Upstream’s antibody targets the TSLP receptor.

Blocking the receptor might be a more efficient way of curtailing inflammation, since there can be many more TSLP molecules than receptors, making it hard for a drug to mop them all up, said Dr. Aaron Deykin, Upstream’s chief medical officer and head of research and development. “That is really a hypothesized potential advantage,” he said.


Deykin joined Upstream in April after a 15-year career at Biogen, where he was most recently the Cambridge company’s senior vice president of clinical sciences. Prior to joining Biogen, Deykin was a leader of the asthma research center at Brigham and Women’s Hospital. He planned to work on respiratory diseases at Biogen, but those programs never became a big focus for the company.

When he was introduced to Upstream’s asthma program, Deykin immediately recognized that “it was very exciting,” he said. Astellas has already tested the antibody’s safety in a small clinical trial, and Upstream will start assessing its efficacy in asthma patients this year. The company ultimately plans to test the drug in other immune diseases driven by TSLP, too.

Upstream isn’t disclosing how much it spent on the Astellas drug or how far into clinical development its existing funds will carry the company. But the large initial financing is particularly notable now given the struggling biotech market, which some investors think is starting to slow and shrink investment in private biotech startups.

“We are fortunate to have that funding in hand, particularly given the situation of the markets now,” Truex said.

Upstream launched at a more advanced stage than many biotech startups, which often go through multiple rounds of funding from venture capital firms before having a drug ready for clinical testing. But with many preclinical stage biotech companies struggling on the public markets, private investors may view startups that have drugs ready for clinical testing as safer bets during the ongoing downturn.


For instance, Cambridge startup Third Harmonic Bio launched with $155 million in February to develop an experimental drug it licensed from Novartis. The drug is in clinical studies for a rare form of chronic hives, but the startup plans to test it in multiple severe allergy and inflammation diseases.

Ryan Cross can be reached at ryan.cross@globe.com. Follow him on Twitter @RLCscienceboss.