City Therapeutics has raised $200 million in its public market debut, reinforcing its focus on RNA interference for diseases beyond liver treatments. The biotech’s initial public offering, priced at $18 per share, sold over 11.1 million shares, exceeding the 9.7 million originally planned. The company began trading Friday under the ticker CTY on Nasdaq.
City Therapeutics’ RNAi Platform Explained
The Cambridge, Massachusetts-based firm specializes in drugs that use small interfering RNA (siRNA) to silence disease-causing genes. While existing RNAi therapies remain limited to liver-targeted applications, City’s platform includes delivery systems capable of reaching other tissues. Its lead program, CITY-FXI, aims to treat blood clot disorders by reducing Factor FXI, a protein in the coagulation pathway. Early Phase 1 results showed a single injection lowered FXI levels by 60% at the lowest dose and 85% at the highest in healthy volunteers.
RNA interference has gained traction as a therapeutic approach. Alnylam Pharmaceuticals, which pioneered the field, now has four FDA-approved RNAi drugs—all for rare liver diseases. City’s co-founder and executive chair, John Maraganore, previously led Alnylam. The company’s IPO filing highlighted the field’s growth, noting roughly 100 programs in clinical development—a trajectory comparable to monoclonal antibodies, which expanded from first approval in the mid-1990s to over 150 approved medicines today.
Expanding Pipeline Beyond Blood Clotting
City’s pipeline includes three clinical-stage programs. Beyond CITY-FXI, the company is developing CITY-RBP4 for Stargardt disease, a rare inherited form of vision loss, and CITY-TFR2 for anemia linked to myelofibrosis. Both are expected to enter Phase 1 trials this year, with data anticipated in early 2028. The company also plans to explore CITY-RBP4 in geographic atrophy, a late-stage dry eye condition.
Strategic partnerships are expanding City’s reach. Bausch + Lomb is collaborating on RNAi therapies for eye diseases. In the first half of this year, the company reported $6.3 million in collaboration revenue. Before its IPO, City had raised nearly $239 million in private funding, including a $99.5 million Series B round last July. Arch Venture Partners holds a 26.7% stake as its largest shareholder.
With IPO proceeds, City estimates its cash runway extends into late 2028. The company has allocated $30 million for CITY-FXI’s Phase 1 trial and a Phase 2 study in total knee arthroplasty patients, who face raised clot risks after surgery. An additional $20 million is budgeted for CITY-RBP4’s Phase 1 work, while $40 million will support CITY-TFR2 studies in China and anemia indications. Roughly $70 million is reserved for advancing its platform and preclinical candidates.
Investor Confidence and Competitive market
The IPO’s success shows growing investor confidence in RNAi as a therapeutic modality. ADARx Pharmaceuticals, another siRNA-focused biotech, raised $535 million in May for programs targeting tissues beyond the liver. City’s focus on delivery systems that overcome liver restrictions positions it to compete in areas like cardiovascular disease, where anticoagulants remain the standard. The company’s Phase 2 test for CITY-FXI in knee surgery patients is scheduled to begin in mid-2027, with results expected in early 2028.
City’s competitive edge lies in its ability to refine tissue-specific delivery. Unlike Alnylam’s liver-focused therapies, its ligands, such as the LRP1-targeting ligand in CITY-FXI, are designed to direct siRNA to non-liver tissues. This approach could unlock treatments for more common diseases, though competition is intensifying. ADARx is advancing an FXI-targeting siRNA for stroke prevention, set to enter mid-stage testing in 2025. City’s Phase 1 data, due later this year, will be critical in assessing whether its delivery strategy can match or surpass rivals.
The Phase 1 trial for CITY-FXI is examining multiple dosing regimens to determine optimal duration and frequency. The study includes healthy volunteers to evaluate safety, tolerability, and FXI knockdown across doses, with an emphasis on identifying the lowest effective dose that maintains therapeutic levels. While dosing intervals remain undisclosed, the trial will explore both single and repeated administrations to guide future studies in patients with raised clot risk. The Phase 2 trial, beginning in mid-2027, will enroll total knee arthroplasty patients to assess whether CITY-FXI reduces venous thromboembolism compared to standard anticoagulants. The primary endpoint will measure clot-related complications within 30 days post-surgery, a period of heightened risk for patients.
Targeting Vision Loss with CITY-RBP4
The CITY-RBP4 program targets RBP4, a protein linked to retinal degeneration in Stargardt disease. The Phase 1 trial, expected to start later this year, will include both healthy volunteers and patients to assess safety and knockdown efficiency. Unlike CITY-FXI, which uses an LRP1 ligand, CITY-RBP4 employs a different tissue-targeting approach designed to penetrate the retina. Early preclinical data suggested the ligand could achieve sustained RBP4 knockdown in retinal cells, though human trial results will determine clinical benefit. If successful, the program could expand into geographic atrophy, where raised RBP4 levels contribute to disease progression. A Phase 2 trial for this indication is planned to start late next year.
City’s delivery platform sets it apart from competitors like ADARx, which is also developing an FXI-targeting siRNA for stroke prevention. While ADARx’s program focuses on secondary stroke prophylaxis, City’s CITY-FXI is exploring broader cardiovascular applications, including atrial fibrillation in patients ineligible for oral blood thinners, extended secondary prophylaxis following venous thromboembolism, and cancer-associated thrombosis.
The Phase 1 data due later this year will reveal whether City’s LRP1 ligand achieves durable FXI knockdown without systemic side effects. ADARx’s mid-stage stroke trial, expected to begin in 2025, will provide a direct comparison for efficacy and safety in high-risk patients. City’s Phase 2 knee surgery study in 2027 will further clarify whether its approach can reduce clot complications in a setting where anticoagulants pose bleeding risks.
