Spero Therapeutics (NASDAQ:SPRO) used its second-quarter update to outline a strategic shift toward immune-mediated diseases, supported by the FDA approval of Utebzi and a new licensing agreement for SP001, an antibody candidate the company plans to develop initially for IgG4-related disease.
President and Chief Executive Officer Esther Rajavelu said the company reached four major milestones during the past 90 days: FDA approval of Utebzi, the in-licensing of SP001, completion of a $105 million royalty financing arrangement, and the appointment of Dr. Debra Jeske Zack as chief medical officer.
Utebzi Approval and Royalty Financing
On June 17, the FDA approved Utebzi, or tebipenem HBr, for the treatment of complicated urinary tract infections, including pyelonephritis, caused by certain susceptible pathogens in patients with limited or no alternative oral treatment options. Rajavelu described Utebzi as the first and only oral carbapenem antibiotic approved in the United States.
The approval was based on the Phase III PIVOT-PO study, which was stopped early for efficacy in May 2025. GSK holds exclusive worldwide commercialization rights for the drug outside certain Asian territories retained by Meiji. GSK expects Utebzi to become available to U.S. patients during the second half of 2026, according to Rajavelu.
Spero subsequently closed a $105 million non-dilutive, non-recourse royalty financing with affiliates of HealthCare Royalty Partners, a business of KKR. A special-purpose subsidiary issued senior secured notes with a 10% annual interest rate and a nine-year maturity. Principal and interest payments will be funded solely by milestone and royalty payments that GSK owes Spero related to Utebzi.
After the notes are repaid, Spero will retain 35% of additional GSK milestone and royalty proceeds. Rajavelu said the financing is non-recourse to Spero and does not expose the company’s other assets to Utebzi launch or sales risks.
Management said its June 30 cash balance, together with proceeds from the financing, is expected to fund the $35 million non-refundable upfront payment to Innovent Biologics as well as operating expenses and capital expenditures into the second half of 2029.
SP001 License Supports Immunology Strategy
On July 8, Spero announced an exclusive license agreement with Innovent Biologics for SP001, also known as IBI355, with an estimated $1.1 billion in total contingent deal value. The agreement gives Spero worldwide development and commercialization rights outside Greater China, where Innovent retains rights.
SP001 is a third-generation, fully humanized Fc-silent IgG1 monoclonal antibody targeting CD40 ligand. The candidate has completed Phase I single-ascending-dose and multiple-ascending-dose studies in healthy volunteers, as well as a Phase Ib multiple-ascending-dose study in patients with primary Sjögren’s disease. Data from the Sjögren’s trial were presented at the EULAR Congress in June.
Zack, who joined Spero on Aug. 3, said CD40 ligand is an upstream immune activation signal involved in interactions among T cells, B cells and antigen-presenting cells. She said blocking the pathway could potentially affect several components of immune-mediated disease, including antibody production, antigen presentation and inflammatory signaling.
Spero intends to advance SP001 first in IgG4-related disease, or IgG4-RD, with a Phase II trial expected to begin in the second quarter of 2027. The company also plans to evaluate additional development opportunities for the asset.
Planned IgG4-RD Study
IgG4-RD is a chronic fibroinflammatory disease that can affect multiple organ systems, including the pancreas, kidneys, salivary and tear glands, aorta and lungs. Zack said untreated or undertreated inflammation can lead to scarring, fibrosis and potentially organ failure.
Spero estimates there are 20,000 to 40,000 diagnosed patients in the United States. Management expects diagnosis rates to increase following the implementation of a disease-specific diagnostic code in October 2023 and anticipated updates to treatment guidelines.
Zack said current treatment can include steroids, disease-modifying antirheumatic drugs, off-label rituximab and recently approved Uplizna. She said patients commonly cycle through remission and relapse as B cells repopulate over time, and that no option currently provides durable long-term disease control.
The planned Phase II trial is expected to be open label, with dosing every six months and two dose arms enrolling up to 15 patients each. Zack said the study is intended to establish proof of concept and will assess symptom control, disease control over time, safety, and potential reductions in steroid and disease-modifying drug use.
“What we are really looking for is that the molecule controls the symptoms and has a good safety profile,” Zack said, adding that the company aims to determine whether other treatments, including steroids, can be reduced.
Second-Quarter Financial Results
- Second-quarter 2026 revenue was zero, compared with $14.2 million in the second quarter of 2025.
- Research and development expense fell to $3.4 million from $10.7 million a year earlier, primarily reflecting reduced clinical activity after Utebzi’s Phase III study concluded early and lower personnel costs.
- General and administrative expense increased to $6.5 million from $5.9 million, driven by higher business development, legal and consulting costs.
- Net loss was $9.6 million, compared with a $1.7 million net loss in the prior-year period.
- Diluted net loss per share was $0.16, compared with $0.03 a year earlier.
Rajavelu said Spero is now moving forward as an immunology-focused company, with SP001 as its lead asset and funding expected to support the company through the second half of 2029.
About Spero Therapeutics (NASDAQ:SPRO)
Spero Therapeutics is a clinical‐stage biopharmaceutical company focused on the discovery and development of novel therapies to address multidrug‐resistant bacterial infections. Headquartered in Boston, Massachusetts, the company aims to advance a pipeline of oral and intravenous antibiotic candidates designed to treat serious infectious diseases that pose significant public health challenges.
The company’s lead candidate, tebipenem HBr, is an oral carbapenem antibiotic being developed for the treatment of complicated urinary tract infections caused by resistant Gram‐negative pathogens.
