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FDA clears Spero (NASDAQ: SPRO) oral Utebzi antibiotic for complicated UTIs

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Rhea-AI Filing Summary

Spero Therapeutics announced that the FDA has approved Utebzi (tebipenem pivoxil), an oral antibiotic for adults with complicated urinary tract infections (cUTIs), including pyelonephritis, who have limited or no alternative oral options. This is the first and only oral carbapenem antibiotic approved for these patients in the US.

The approval stems from a global development and exclusive licensing agreement with GSK and was granted ahead of the Prescription Drug User Fee Act date of June 18, 2026. Phase III PIVOT-PO data showed oral tebipenem pivoxil was non-inferior to intravenous imipenem-cilastatin, with a generally similar safety profile.

Positive

  • FDA approval of Utebzi as the first and only oral carbapenem for adults with complicated urinary tract infections in the US represents a major milestone that could unlock a large, underserved market and validates more than a decade of development work with GSK support and BARDA funding.

Negative

  • None.

Insights

FDA approval of Utebzi is a pivotal value inflection for Spero.

The FDA has approved Utebzi (tebipenem pivoxil) as the first and only oral carbapenem for adults with complicated UTIs who lack good oral options. This targets a large US burden of over 3 million cUTI cases annually and more than $6 billion in related healthcare costs.

The drug was developed under an exclusive global license with GSK (excluding select Asian territories), with GSK holding the NDA sponsorship. Phase III PIVOT-PO showed a 58.5% overall success rate for oral tebipenem pivoxil versus 60.2% for IV imipenem-cilastatin, meeting the predefined non-inferiority margin with a broadly comparable safety profile.

Utebzi carries Qualified Infectious Disease Product and Fast Track designations and is anticipated to be available to US patients by the end of 2026. The collaboration structure, and GSK’s right to determine future development and commercialization, means commercial outcomes will depend heavily on GSK’s execution and market acceptance, as highlighted in the forward-looking risk factors.

Item 7.01 Regulation FD Disclosure Disclosure
Material non-public information disclosed under Regulation Fair Disclosure, often investor presentations or guidance.
Item 8.01 Other Events Other
Voluntary disclosure of events the company deems important to shareholders but not covered by other items.
Item 9.01 Financial Statements and Exhibits Exhibits
Financial statements, pro forma financial information, and exhibit attachments filed with this report.
US cUTI cases More than 3 million cases per year Annual burden of complicated urinary tract infections in the US
Treatment failure rate Up to 34% of patients Proportion of cUTI patients experiencing treatment failure
cUTI healthcare costs Over $6 billion per year Estimated annual US healthcare costs linked to cUTIs
Tebipenem overall success 58.5% (261/446 participants) Overall response in PIVOT-PO trial at test-of-cure visit
Imipenem-cilastatin success 60.2% (291/483 participants) Comparator overall response in PIVOT-PO trial
Non-inferiority margin -10% Predefined NI margin in PIVOT-PO design
Adjusted treatment difference -1.3% (95% CI: -7.5%, 4.8%) Tebipenem vs imipenem-cilastatin overall success in PIVOT-PO
Trial enrollment 1,690 patients Total participants in the PIVOT-PO phase III trial
carbapenem medical
"This is the first and only oral carbapenem antibiotic approved for these patients."
Carbapenems are a class of powerful antibiotics used to treat severe or hard-to-treat bacterial infections, often reserved when other drugs no longer work. For investors, they matter because their clinical effectiveness, regulatory approvals, and the growing problem of bacterial resistance can strongly influence a drug’s market value, hospital demand, pricing power, and the commercial prospects of companies developing or selling new or improved versions.
Qualified Infectious Disease Product regulatory
"tebipenem pivoxil has received Qualified Infectious Disease Product and Fast Track designations"
A qualified infectious disease product is a drug or biologic given a special regulatory label because it targets serious or life‑threatening infections and meets public‑health needs. The label brings incentives such as faster regulatory review, development tax benefits, and extra time with market exclusivity—think of it as a VIP pass and an extended storefront lease that can speed approval and delay generic competition. For investors, that can raise a candidate’s commercial value, lower development risk and make partnerships or buyouts more likely.
Fast Track regulatory
"tebipenem pivoxil has received Qualified Infectious Disease Product and Fast Track designations from the US FDA."
A fast track designation is a regulatory label that speeds up the review and communication between a drug developer and regulators for treatments addressing serious illnesses or unmet medical needs. For investors, it matters because it can shorten development time and reduce regulatory delays—like getting a VIP lane at the airport—raising the chance of earlier market access and potential revenue, though it does not guarantee approval.
PIVOT-PO trial medical
"This approval is supported by positive results from the PIVOT- phase III trial"
Prescription Drug User Fee Act (PDUFA) regulatory
"FDA approval was received in advance of FDA-assigned Prescription Drug User Fee Act ("PDUFA") date of June 18, 2026."
The Prescription Drug User Fee Act (PDUFA) is a law that allows drug companies to pay fees to the government to help speed up the review process for new medicines. This funding aims to ensure that important drugs reach patients faster, which can influence a company's ability to bring products to market efficiently. For investors, PDUFA-related decisions can impact drug approval timelines and company performance.
complicated urinary tract infections (cUTIs) medical
"an oral antibiotic for the treatment of complicated urinary tract infections (cUTIs) including pyelonephritisa"
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false 0001701108 0001701108 2026-06-17 2026-06-17
 
 

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

 

 

FORM 8-K

 

 

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 17, 2026

 

 

SPERO THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

 

 

 

Delaware   001-38266   46-4590683

(State or other jurisdiction

of incorporation)

 

(Commission

File Number)

 

(I.R.S. Employer

Identification No.)

 

675 Massachusetts Avenue, 14th Floor  
Cambridge, Massachusetts   02139
(Address of principal executive offices)   (Zip Code)

Registrant’s telephone number, including area code (857) 242-1600

 

 

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

 

Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

 

Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

 

Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

 

Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

 

Title of each class

 

Trading

Symbol(s)

 

Name of each exchange

on which registered

Common Stock, $0.001 par value   SPRO   The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

 

 
 


Item 7.01

Regulation FD Disclosure

On June 17, 2026, Spero Therapeutics, Inc. (the “Company”) issued a press release announcing that the U.S. Food and Drug Administration (“FDA”) has granted approval for Utebzi (tebipenem pivoxil), an oral antibiotic for the treatment of complicated urinary tract infections (“cUTIs”), including pyelonephritis, caused by certain susceptible pathogens in adult patients who have limited or no alternative oral treatment option.

The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated into this Item 7.01 by reference.

The information in this Item 7.01 and Exhibit 99.1, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section or sections 11 and 12(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”), nor shall it be deemed incorporated by reference in any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such filing.

 

Item 8.01

Other Events.

On June 17, 2026, the Company issued a press release announcing that the FDA has granted approval for Utebzi (tebipenem pivoxil), an oral antibiotic for the treatment of cUTIs, including pyelonephritis, caused by certain susceptible pathogens in adult patients who have limited or no alternative oral treatment option. This is the first and only oral carbapenem antibiotic approved for these patients. This approval is a result of GSK’s development and exclusive global licensing agreement (excluding select Asian territories) with the Company. FDA approval was received in advance of FDA-assigned Prescription Drug User Fee Act (“PDUFA”) date of June 18, 2026.

 


Item 9.01

Financial Statements and Exhibits

 

(d)

Exhibits

 

Exhibit No.   

Description

99.1    Press release issued by Spero Therapeutics, Inc. on June 17, 2026
104    Cover Page Interactive Data File (embedded within the Inline XBRL document and incorporated as Exhibit 101)

 


SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

 

Date: June 22, 2026     SPERO THERAPEUTICS, INC.
    By:  

/s/ Esther Rajavelu

      Esther Rajavelu
      Chief Executive Officer, Chief Financial Officer and Chief Business Officer

Exhibit 99.1

Utebzi (tebipenem pivoxil) approved in the US for adults with complicated urinary tract infections (cUTIs)

 

   

First and only oral carbapenem antibiotic approved in the US

 

   

Approval based on PIVOT-PO trial demonstrating non-inferiority compared to intravenous treatment1

 

   

More than 3 million cases of cUTIs are treated annually in the US with a third of patients impacted by resistant infections2,3

CAMBRIDGE, Mass., June 17, 2026Spero Therapeutics, Inc. (Nasdaq: SPRO) and GSK plc (LSE/NYSE: GSK) today announced that the US Food and Drug Administration (FDA) has approved Utebzi, an oral antibiotic for the treatment of complicated urinary tract infections (cUTIs) including pyelonephritisa, caused by certain susceptible pathogensb in adult patients who have limited or no alternative oral treatment options. This is the first and only oral carbapenem antibiotic approved for these patients. This approval is a result of GSK’s development and exclusive global licensing agreement (excluding select Asian territories) with Spero Therapeutics.4

There are more than 3 million cases of cUTI in the US annually and treatment failure impacts up to 34% of patients.2,3 Often caused by multidrug-resistant pathogens,5 these infections account for over $6 billion per year in healthcare costs.3 Carbapenems are the standard treatment for severe or resistant infections, but until now have only been available through intravenous administration6, increasing hospital resource use and reducing patients’ quality of life.7 Tebipenem pivoxil offers the potential for an effective oral alternative taken outside of a hospital setting.

Tony Wood, Chief Scientific Officer, GSK, said: “With antibiotic resistance continuing to rise, patients and healthcare professionals need new treatment options. The approval of Utebzi provides the first and only oral carbapenem antibiotic for appropriate adults with complicated UTIs, a solution that could help reduce reliance on hospital-based intravenous care and support efforts to address resistant infections.”

Dr. Bilal Chughtai, Chief of Urology at Plainview Hospital, Northwell Health and Associate Professor of Urology at the Zucker School of Medicine at Hofstra/Northwell, said: “For patients with complicated urinary tract infections (cUTIs) and their caregivers, this approval is a major milestone as today’s standard of care places a serious burden on them and hospitals. A new effective oral treatment offering an alternative option to intravenous care has the potential to enable more treatment in the outpatient settings with the ambition to improve their experience.”

Esther Rajavelu, President and Chief Executive Officer, Spero Therapeutics added: “The FDA approval of tebipenem pivoxil marks the culmination of more than a decade of dedication from our team, partners, and, most importantly, the patients who placed their trust in this program. We are proud to reach this important milestone. Through our partnership with GSK, we look forward to this much-needed oral treatment option reaching cUTI patients to help reduce the burden of the disease.”

 
a

Pyelonephritis is a specific type of UTI that has travelled up the urinary tract to infect one or both kidneys.

b

Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae species complex, Klebsiella oxytoca, and Enterococcus faecalis.


This approval is supported by positive results from the PIVOT-PO phase III trial, which demonstrated non-inferiority of tebipenem pivoxil compared to intravenous imipenem-cilastatin in hospitalized patients with cUTI, including pyelonephritis, based on the overall response (composite of clinical cure plus microbiological eradication) at the test of cure visit. Tebipenem pivoxil (oral, 600 mg) achieved a 58.5% overall success rate (261/446 participants) compared to 60.2% overall success rate (291/483 participants) for imipenem-cilastatin (intravenous, 500 mg) (adjusted treatment difference: -1.3%; 95% CI: -7.5%, 4.8%).

The safety profile of tebipenem pivoxil was generally similar to that of imipenem-cilastatin and other carbapenem antibiotics. The most frequently reported adverse events (in ≥3% of patients) were diarrhoea and headache; these events were all mild or moderate and non-serious.8

Tebipenem pivoxil is anticipated to be made available to US patients by the end of 2026.

This approval confirms the successful and productive collaboration between GSK and Spero Therapeutics. The development of tebipenem pivoxil has been supported in part with federal funds from the US Department of Health and Human Services; Administration for Strategic Preparedness and Response; Biomedical Advanced Research and Development Authority (BARDA), under contract numbers HHSO100201800015C and HHSO100201300011C.

About tebipenem pivoxil

Tebipenem pivoxil was developed in collaboration with Spero Therapeutics9 for the treatment of cUTIs, including pyelonephritis. In September 2022, GSK entered into an exclusive license agreement with Spero Therapeutics for the development and commercialization in all markets, except certain Asian territories. Under this agreement, GSK sub-licensed back to Spero Therapeutics the rights and responsibility to conduct certain development work, including the PIVOT-PO phase III study. The sponsorship of the New Drug Application has been transferred to GSK. As part of the license agreement, tebipenem pivoxil has received Qualified Infectious Disease Product and Fast Track designations from the US FDA.

The US Prescribing Information will be available here [https://gskpro.com/content/dam/global/hcpportal/en_US/Prescribing_Information/Utebzi/pdf/UTEBZI-PI-PIL.PDF]

About the PIVOT-PO trial

The PIVOT-PO trial was a global, randomized, double-blind, pivotal, non-inferiority (NI margin: -10%) phase III trial evaluating the potential of oral tebipenem pivoxil compared to IV imipenem-cilastatin, in hospitalized adult patients with complicated urinary tract infections, including acute pyelonephritis. Patients were randomized 1:1 to receive tebipenem pivoxil (600 mg) orally every six hours, or imipenem-cilastatin (500 mg) IV every six hours, for a total of seven to ten days. Dose adjustments were made for patients with reduced renal function. Matching placebos were used to maintain


blinding. The primary efficacy endpoint was composite response (combined per-patient clinical cure and microbiological response) at the test-of-cure visit (about 17 days from first dose administration of study drug) in patients with qualifying pathogens susceptible to imipenem. The trial enrolled a total of 1,690 patients, with randomization stratified by age, baseline diagnosis (cUTI or acute pyelonephritis), and the presence or absence of urinary tract instrumentation. For further details on the trial, refer to clinicaltrials.gov identifier NCT06059846.10

About complicated urinary tract infections (cUTIs)

cUTIs are broadly described as any UTI that carries an increased risk of morbidity and mortality.5 Definitions of cUTIs are not currently uniform among international societies and regulatory agencies. cUTIs encompass a heterogeneous patient population due to the wide range of host factors, comorbidities and urological abnormalities associated with cUTIs. Risk factors for cUTIs include indwelling catheters, ureteric stents, neurogenic bladder, obstructive uropathy, urinary retention, urinary diversion, kidney stones, diabetes mellitus, immune deficiency, urinary tract modification and UTIs in renal transplant patients.11,12,13,14

About GSK

GSK is a global biopharma company with a purpose to unite science, technology and talent to get ahead of disease together. Find out more at gsk.com.

About Spero Therapeutics

Spero Therapeutics, headquartered in Cambridge, Massachusetts, is a clinical-stage biopharmaceutical company focused on identifying and developing novel treatments for rare diseases and diseases with high unmet need. For more information, visit www.sperotherapeutics.com.

Forward Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, statements regarding the potential Utebzi to meaningfully improve treatment options for cUTI patients; the potential of Utebzi to help reduce reliance on hospital-based intravenous care and support efforts to address resistant infections; the potential of Utebzi to enable more treatment options in outpatient settings with the ambition to improve patients’ experience; the potential of tebipenem HBr to set a new standard of care and decrease the disease burden. In some cases, forward-looking statements may be identified by terms such as “may,” “will,” “should,” “expect,” “plan,” “aim,” “anticipate,” “could,” “intent,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue,” the negative of these terms or other similar expressions. Any forward-looking statements in this press release are based on management’s current expectations and beliefs and are subject to a number of important risks, uncertainties and other factors that may cause actual results to differ materially from those indicated by such forward looking statements, including, but not limited to, whether Spero and GSK will successfully perform their respective obligations under the collaboration between Spero and GSK; risks and uncertainties related to the successful commercial launch of Utebzi and market acceptance; the competitive landscape for Utebzi, risks related to Spero’s expectations regarding the potential clinical benefit of Utebzi to patients; the risk that any regulatory approval may be subject to significant


limitations on use or subject to withdrawal or other adverse actions by the applicable regulatory authority; the uncertainties inherent in research and development, including clinical results; regulatory actions or delays or government regulation generally; Spero’s ability to protect its intellectual property portfolio; Spero’s reliance on third parties to manufacture, develop, and commercialize its product candidates; Spero’s reliance on GSK, pursuant to the exclusive GSK License Agreement, to advance development of tebipenem pivoxil and GSK’s right thereunder to determine, in its sole discretion, whether to further develop and commercialize tebipenem pivoxil; Spero’s need for additional funding; Spero’s ability to retain key personnel; whether Spero’s cash resources will be sufficient to fund its continuing operations for the periods anticipated; and other factors discussed in the “Risk Factors” set forth in filings that Spero periodically makes with the SEC. The forward-looking statements included in this press release represent Spero’s views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, Spero explicitly disclaims any obligation to update any forward-looking statements.

Investor Relations Contact:

Shai Biran, PhD

Spero Therapeutics

IR@Sperotherapeutics.com

Media Inquiries:

media@sperotherapeutics.com

 
1 

GSK press release, “Positive PIVOT-PO phase III data show tebipenem HBr’s potential as the first oral carbapenem antibiotic for patients with complicated urinary tract infections (cUTIs)”, October 2025. Available at: press-release-tebi-pivot-po-phase-iii-read-out.pdf (last accessed: May 2026)

2 

Carreno JJ, et al. “Longitudinal, nationwide, cohort study to assess incidence, outcomes, and costs associated with complicated urinary tract infection” in Open Forum Infect Dis. 2019;7:ofil446. doi: 10.1093/ofid/ofz446

3 

Lodise TP, et al. Hospital admission patterns of adult patients with complicated urinary tract infections who present to the hospital by disease acuity and comorbid conditions: How many admissions are potentially avoidable? Am J Infect Control. 2021;49(12):1528-1534.

4 

GSK press release, GSK and Spero Therapeutics announce exclusive licence agreement for tebipenem HBr, a late-stage antibiotic that may treat complicated urinary tract infections, 22 September 2022

5 

Sabih A, Leslie SW. “Complicated urinary tract infections” in StatPearls. 2023. StatPearls Publishing: Treasure Island, FL, USA.

6 

Eckburg PB, et al. “Oral tebipenem pivoxil hydrobromide in complicated urinary tract infection”. In New England Journal of Medicine,. 2022;386:1327-1338. doi: 10.1056/NEJMoa2105462

7 

NHS. Reducing complications with a prolonged hospital stay. 2024. Available from: https://www.plymouthhospitals.nhs.uk/display-pil/pil-reducing-complications-with-a-prolonged-hospital-stay-6686 (last accessed: May 2026)

8 

GSK press release, Positive PIVOT-PO phase III data show tebipenem HBr’s potential as the first oral carbapenem antibiotic for patients with complicated urinary tract infections (cUTIs), October 2025

9 

GSK press release, GSK and Spero Therapeutics announce exclusive licence agreement for tebipenem HBr, a late-stage antibiotic that may treat complicated urinary tract infections, 22 September 2022

10 

CT.gov, A Study of Oral Tebipenem Pivoxil Hydrobromide (TBP-PI-HBr) Compared to Intravenous Imipenem-cilastatin in Participants With Complicated Urinary Tract Infection (cUTI) or Acute Pyelonephritis (AP) (PIVOT-PO), last updated on 01 July 2025

11 

Bonkat G, et al. “Keep it Simple: A Proposal for a New Definition of Uncomplicated and Complicated Urinary Tract Infections from the EAU Urological Infections Guidelines Panel”. Eur Urol. 2024;86(3):195-197.

12 

Wagenlehner FME, et al. Epidemiology, definition and treatment of complicated urinary tract infections. Nat Rev Urol. 2020;17(10):586-600.

13 

Gomila A, et al. Predictive factors for multidrug-resistant gram-negative bacteria among hospitalized patients with complicated urinary tract infections. Antimicrob Resist Infect Control. 2018;7:111.

14 

Altunal N, et al. Ureteral stent infections: a prospective study. Braz J Infect Dis. 2017;21(3):361-364.

FAQ

What did Spero Therapeutics (SPRO) announce regarding Utebzi?

Spero Therapeutics announced that the FDA has approved Utebzi (tebipenem pivoxil), an oral antibiotic for adults with complicated urinary tract infections. The drug targets patients with limited or no alternative oral treatment options and is the first approved oral carbapenem for this population.

Why is Utebzi’s FDA approval important for complicated UTI treatment?

Utebzi is the first and only oral carbapenem approved for adults with complicated UTIs, including pyelonephritis, who lack good oral options. Previously, carbapenems were only available intravenously, increasing hospital resource use and affecting patient quality of life and healthcare costs.

How effective was tebipenem pivoxil in the PIVOT-PO phase III trial?

In the PIVOT-PO phase III trial, tebipenem pivoxil 600 mg orally achieved a 58.5% overall success rate versus 60.2% for IV imipenem-cilastatin 500 mg. The adjusted treatment difference of -1.3% (95% CI: -7.5%, 4.8%) met the predefined non-inferiority margin of -10%.

What safety profile did Utebzi show in clinical studies?

Tebipenem pivoxil showed a safety profile generally similar to imipenem-cilastatin and other carbapenems. The most frequently reported adverse events, occurring in at least 3% of patients, were diarrhoea and headache, and these events were described as mild or moderate and non-serious.

What is the market opportunity for Utebzi according to Spero Therapeutics?

The press release cites more than 3 million cUTI cases annually in the US, with treatment failure affecting up to 34% of patients and accounting for over $6 billion in yearly healthcare costs. Utebzi offers an oral option that may shift some care from inpatient IV settings to outpatient treatment.

When is Utebzi expected to be available to US patients?

Utebzi is anticipated to be available to US patients by the end of 2026. This follows FDA approval granted ahead of the Prescription Drug User Fee Act (PDUFA) date of June 18, 2026, and is tied to GSK’s commercialization efforts under its exclusive license with Spero.

What is the nature of the GSK–Spero collaboration on tebipenem pivoxil?

GSK entered an exclusive license agreement with Spero in September 2022 for development and commercialization of tebipenem pivoxil outside certain Asian territories. GSK sponsors the New Drug Application, while Spero sub-licensed rights to conduct certain development work, including the PIVOT-PO phase III study.

Filing Exhibits & Attachments

4 documents