‘Reverse mergers are increasingly popular’: Caldera hops on Synlogic’s Nasdaq listing

Biotech ‘Reverse mergers are increasingly popular’: Caldera hops on Synlogic’s Nasdaq listing By Nick Paul Taylor Jul 29, 2026 8:56am Synlogic reverse merger inflammatory bowel disease ulcerative colitis Caldera Therapeutics has struck a reverse merger with the Nasdaq-listed Synlogic and inked a $278 million financing deal, continuing the meteoric rise of the inflammatory bowel disease (IBD) startup. Massachusetts-based Caldera, which began operations last year, exited stealth in January with $112.5 million and a bispecific antibody licensed from China’s Qyuns Therapeutics. By then, the biotech had already taken the bispecific, CLD-423, into a phase 1 trial.

The drug candidate hits the IL-23p19 and TL1A pathways, targets that are respectively engaged by AbbVie’s Skyrizi and Merck & Co.’s tulisokibart. “We always had a view that, while the currently approved monotherapies met a good unmet need, there was still a lot more left on the table from an efficacy perspective,” Aaron Pelta, chief business officer at Caldera, told Fierce this morning. “In recent years, there’s been clinical trials that have shown combining complementary mechanisms through a combination approach has really given a step up in efficacy.” Caldera is one of several companies to recognize the potential of hitting both targets with one molecule.

Operating in a competitive space, the biotech is moving quickly, building on its early progress with deals to secure a public listing and enough cash to fund operations into 2029. The deal values Synlogic at $18 million, assuming it has $6 million in net cash when the merger closes, and Caldera at $500 million. Synlogic shareholders will own 2.3% of the combined biotech, and Caldera’s existing investors will hold a 62.8% stake.

Investors in a $278 million private placement, which Caldera has lined up alongside the reverse merger, will own the other 34.9%. Bain Capital Life Sciences, TCGX and Atlas Venture are among the backers to commit cash to the private placement. The decision to fund the company through a private investment in public equity (PIPE) reflects a desire to “strike while the iron's hot,” Pelta said.

“We thought we would be doing a series B at the end of this year to fund our phase 2 program. But the markets have really turned in a positive way in the last few months and these PIPE reverse mergers are becoming increasingly popular,” Pelta said. “We decided to go for the public markets where we can get much broader investor exposure [and] get more appreciation from a value perspective.” Caldera will use the money to run phase 2 trials of CLD-423 in ulcerative colitis and Crohn’s disease.

A phase 1 trial in healthy volunteers has completed dosing, giving Caldera evidence that the bispecific is well tolerated, has about 80% subcutaneous bioavailability and could support maintenance dosing once every eight or 12 weeks. Caldera plans to share more data from the trial later this year. As a clinical-phase candidate, CLD-423 is at the front of the TL1AxIL23p19 race, which includes assets in development at Boehringer Ingelheim, Elpiscience, Novamab Biopharmaceuticals and Xencor.

Boehringer joined the race in January by betting up to 1.05 billion euros ($1.2 billion) on Simcere’s SIM0709. The level of competition is informing Caldera’s clinical development strategy. “The goal is to optimize for time to market.

It’s a competitive space. We’re first, we want to stay first,” Pelta said. “We’re also wanting to optimize for time to clinical proof-of-concept.

We want to be the first out there with a robust clinical dataset in IBD patients.” Caldera plans to run a global, placebo-controlled phase 2b trial in ulcerative colitis. In parallel, the team is working with its Chinese partner to start an open-label phase 2 Crohn’s trial early next year. Running an open-label trial in China is “probably the best way to quickly and effectively enroll Crohn’s patients,” Pelta said.

The Caldera deal marks the end of the road for Synlogic, a synthetic biology startup that went public in 2017 via a reverse merger with Mirna Therapeutics. The biotech has been in stasis since February 2024, when the failure of a phase 3 trial triggered deep layoffs and a hunt for strategic alternatives. The layoffs left the company with one full-time employee.

Synlogic reverse merger inflammatory bowel disease ulcerative colitis Crohn's disease Emerging Biopharma bispecific antibodies Biotech Deals