PlateletBio, a company developing a new class of cell therapies based on the biology of platelets, has raised $75.5 million to advance its drug pipeline, including a lead candidate for a rare bleeding disorder on track to reach the clinic next year.

Platelets are components of blood best known for their role forming clots that stop bleeding. But Watertown, Massachusetts-based PlateletBio notes that platelets have other properties, including a role delivering growth factors and proteins throughout the body. PlateletBio is developing therapies that take advantage of these properties, but rather than using platelets from a patient or healthy donors, the startup makes them.

In the body, platelets are formed in bone marrow. PlateletBio produces its platelet-like cells, or PLCs, inside a bioreactor that mimics bone marrow conditions. The source material for its PLCs are stem cells, which have the ability to become almost any cell or tissue in the body.

Platelets are technically not cells. They dont have a nucleus, but thats an advantage for therapeutic applications. Since a PlateletBio therapy wont introduce DNA into a patients body, the potential risks that come from introducing foreign genetic material are avoided. PlateletBio says it can produce PLCs with new features and therapeutic payloads that include antibodies, signaling proteins, therapeutic proteins, and nucleic acids.

PlateletBios lead cell therapy candidate is being developed to treat immune thrombocytopenia, a blood disorder in which the immune system mistakenly sees a patients platelets as foreign and destroys them. Immune thrombocytopenia patients have dangerously low platelet counts that make them susceptible to bleeding.

There is no FDA-approved treatment for the underlying cause of immune thrombocytopenia, but corticosteroids are used to try to dampen the immune systems attack on platelets. Platelet transfusions are another option, but the National Organization for Rare Disorders notes that these treatments are usually reserved for emergencies because the platelets are likely to be destroyed by antibodies produced by the patient.

Patients who have not responded to earlier treatments have two FDA-approved small molecule options: Tavalisse, from Rigel Pharmaceuticals, and the Swedish Orphan Biovitrum drug Doptelet. Sanofi aims to treat the disease with a small molecule called rilzabrutinib. That drug is designed to block Brutons tyrosine kinase, a protein that plays a role in the development of a B cells, a type of immune cell. Sanofi acquired the molecule last year via its $3.7 billion acquisition of Principia Biopharma.

The lead disease target for the Principia drug was multiple sclerosis. In September, Sanofi reported that rilzabrutinib failed that Phase 3 study. A separate Phase 3 test in immune thrombocytopenia is ongoing, as is a mid-stage clinical trial in another autoimmune condition called IgG4-related disease.

PlateletBio isnt the only company trying to turn a component of the blood into a new type of cell therapy. Cambridge, Massachusetts-based Rubius Therapeutics is developing cell therapies based on red blood cells. After disappointing early clinical trial results in the rare disease phenylketonuria last year, Rubius shifted its focus to cancer and immune system disorders. PlateletBios PLCs would represent an entirely new approach to treating immune thrombocytopenia. According to PlateletBios website, the company plans to file an investigational new drug application for its therapeutic candidate in the first half of next year.

PlateletBio is based on the research of Harvard University scientist Joseph Italiano, who co-founded the company under the name Platelet BioGenesis. When the startup emerged in 2017, it was developing platelets that could address the platelet shortage problem facing blood donation centers. Two years ago, the startup expanded its Series A round with $26 million in additional financing and plans to make its platelets into cell therapies. Besides immune thrombocytopenia, other diseases the biotech aims to treat include osteoarthritis and liver fibrosis.

PlateletBios latest financing, a Series B round, adds new investors SymBiosis, K2 HealthVentures, and Oxford Finance. Earlier investors Ziff Capital Partners and Qiming Venture Partners also participated in the new round.

This is a major milestone for PlateletBio, adding capital and resources needed to advance our innovative platelet-like cell therapy science and manufacturing platform and support key corporate initiatives over the next 18 to 24 months, Sam Rasty, the startups president and CEO, said in a prepared statement.

Photo by Flickr user Marco Verch via a Creative Commons license

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Cell therapy biotech PlateletBio reels in $75M as it looks ahead to first clinical test - MedCity News