Bonum Therapeutics is moving into new offices near Seattle’s South Lake Union neighborhood and plans to double its headcount in pursuit of immunotherapy drugs. The biotech startup will occupy the 11th floor of the Alexandria’s new life science tower at 1150 Eastlake Ave. E.
“We’re very excited about 1150,” said CEO John Mulligan. “It’s beautiful, great views. It’ll be a really fun space.”
Mulligan said Bonum discovered the vacancy during the biotech downturn in 2022. The Alexandria building is in an area of Seattle that’s home to multiple biotech startups and life science research organizations, such as Fred Hutchinson Cancer Research and The Allen Institute.
Bonum will move in August from its current offices in the nearby Access to Advanced Health Institute. Mulligan hopes to double the 31-person team within the next few years.
Mulligan launched Bonum’s predecessor, Good Therapeutics, in 2016 to design cancer drugs with fewer side effects. The startup was acquired by Roche in 2022 for $250 million. The deal gave Roche exclusive rights to Good Therapeutics’ most promising preclinical drug candidate for further development.
Mulligan spun out Bonum from Good Therapeutics about a year and a half before the Roche acquisition, retaining the rights to its other projects and the basic blueprint for the drug it sold to Roche. The entire Good Therapeutics team, including its equipment and data, moved to Bonum after the sale. Bonum raised $93 million just after launch, which is now helping finance its expansion.
Bonum researchers are developing immunotherapy treatments that activate a person’s immune system to fight cancer. While the drugs can be a powerful weapon in battling cancer, they can also have toxic side effects. To avoid causing collateral damage, the company pairs its cancer drugs with sensors that direct the therapeutic to specific cells, Mulligan said.
Bonum’s approach uses small proteins called cytokines, which are messenger molecules that tell the immune system when and where to attack. Good Therapeutics’ first successful drug paired a cytokine called Interleukin-2 with an antibody to another protein called PD1, which acts as the sensor.
Interleukin-2 has been used in people for decades, but “it’s incredibly toxic,” said Mulligan. Around 10% of the people who receive treatment get years of life back, but the other 90% “just get really, really sick,” he added. Interleukin-2 can cause a person’s blood vessels to leak, filling their lungs with fluid and causing bloating and dangerous blood pressure changes.
Given the side effects, the drug is no longer used in its original form, but Interleukin-2 is a target for several drug companies working on modifications that would decrease the toxicity without compromising the benefits.
Unleashing the immune system to fight cancer has been the “big cool thing” in oncology this decade, said Mulligan. But what makes Bonum’s platform unique is the “exquisite specificity to certain cell types,” he added. “That gives us an edge.”
Now the startup is working on a new type of Interleukin-2 drug, paired with a sensor antibody to a protein called LAG3. Mulligan said making new drugs is kind of like building with Legos. They engineer several protein candidates, then test different modifications to make something both easy to manufacture and safe for patients.
While hopeful about the new drug’s potential, the team is also exploring partnerships outside cancer immunotherapy. Its platform could be used to make drugs for treating metabolic conditions, pain and autoimmune diseases.
“The really exciting thing about working on something like this is that you get to do stuff that will, with any luck, have an impact on people,” said Mulligan. “A few years from now, we might see people who are living longer because of the stuff we’re doing right now.”
Editor’s note: This story has been updated to clarify that the Interleukin-2 drugs are each paired with a specific antibody in order to target the treatment.
