Nimbus Therapeutics raises $125m to test drug in psoriasis, lupus, and other diseases

Nimbus Therapeutics chief executive Jeb Keiper.Nimbus Therapeutics

Nimbus Therapeutics said Monday that it raised $125 million in private financing to test its experimental therapies in autoimmune diseases and cancer. The Cambridge biotech’s most advanced program is a pill that it believes could become a treatment for psoriasis, lupus, inflammatory bowel diseases, and other conditions.

The new financing for the 13-year-old private company comes on the heels of the Food and Drug Administration’s approval of Sotyktu, a once-daily pill made by Bristol Myers Squibb to treat moderate-to-severe plaque psoriasis, which affects about two million people in the US.

Bristol Myers Squibb’s Sotyktu and Nimbus’s experimental pill are both designed to inhibit an enzyme called tyrosine kinase 2, or TYK2. People with genetic mutations in these enzymes are far less likely to develop inflammatory or autoimmune diseases.

By creating medicines that mimic those mutations, drug companies and their investors are betting that TYK2 inhibitors could become a major new class of blockbuster drugs for a wide range of autoimmune and inflammatory conditions.

BMS is testing Sotyktu in Phase 3 clinical trials for psoriatic arthritis and Phase 2 clinical trials for Crohn’s disease, ulcerative colitis, and systemic lupus erythematosus. Nimbus has equally broad ambitions for its own TYK2 inhibitors.

One major challenge in the development of these drugs was finding a compound that only inhibited TYK2 and not closely related enzymes in the Janus tyrosine kinase, or JAK, family, said Nimbus chief executive Jeb Keiper.

Some existing JAK inhibitors, approved for conditions such as rheumatoid arthritis and ulcerative colitis, come with FDA-mandated black box warnings that the medicines may increase the risk of heart attack, stroke, blood clots, and cancer.

Drugs that only inhibit TYK2, and no other JAK enzymes, may be safer. In what Keiper calls a major vindication of that hypothesis, the FDA did not require Bristol Myers Squibb to include a black box warning on Sotyktu.

Keiper said that Nimbus’s compound is 13,000 times more selective for TYK2 than the Bristol Myers Squibb drug. That higher selectivity could make it safer and more effective, but it won’t necessarily eliminate all side effects. TYK2 plays a role in the immune system’s ability to fight infections, and Bristol Myers Squibb found that upper respiratory tract infections were more frequent in people taking Sotyktu in clinical trials.

Nimbus’s new financing will help his firm wrap up ongoing Phase 2 clinical trials of its TYK2 inhibitor in plaque psoriasis and psoriatic arthritis, Keiper said. A Phase 3 trial for those conditions is planned for next year, along with Phase 2 trials testing the drug in people with inflammatory bowel diseases and lupus, he added. The company has earlier stage programs of different drugs for cancer as well.

Nimbus once made a splash in Boston’s biotech industry by claiming to design its drugs entirely on computers — a proposition that’s become more common among biotech startups focused on artificial intelligence and machine learning.

To this day, Nimbus has never had its own laboratories, preferring to focus on computational work in-house and outsource any preclinical lab experiments required before the company can begin clinical trials, Keiper said. “We often get surprised looks,” he said.

The company’s big break came in 2016 when Gilead Sciences paid Nimbus $400 million for an early-stage liver disease drug program, with a potential $800 million in milestone payments.

Although Nimbus wouldn’t disclose the exact sum its raised in total, public disclosures indicate the firm has now raised more than $420 million from private financings since its inception. Nimbus has no plans to go public anytime soon. “I would never say never,” Keiper said. “But that’s certainly not the path right now.”

Keiper said the company has kept its investors happy by paying them dividends. Nimbus’s latest financing includes several returning investors, including the venture capital arm of pharma giant Pfizer, the Cambridge-based life sciences venture capital firm Atlas Ventures, and billionaire Bill Gates.

Nimbus has about 80 full-time employees at its offices by Central Square in Cambridge, although Keiper said that the company often has about 200 people working for the firm as consultants or through contract research organizations.