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SPRO Stock Soars 245% on GSK-Partnered UTI Drug Meeting Study Goal

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Shares of Spero Therapeutics (SPRO - Free Report) more than tripled in market value yesterday after a phase III study evaluating its investigational oral antibiotic for complicated urinary tract infections (cUTIs) was stopped early due to efficacy. The drug, called tebipenem HBr, is being developed in partnership with GSK plc (GSK - Free Report) .

This late-stage study, called PIVOT-PO, enrolled hospitalized adult patients with cUTIs, including pyelonephritis (a type of kidney infection). The decision to stop the study early was made following a recommendation from an independent committee, which found that the study met its primary endpoint of non-inferiority. In other words, treatment with tebipenem was as effective as intravenously (IV) administered antibiotic imipenem-cilastatin, a commonly prescribed treatment for cUTIs. These findings are based on an interim analysis of data from 1,690 patients enrolled in the study.

Based on the positive results, Spero’s partner, GSK, plans to submit a regulatory filing seeking approval for the drug with the FDA later this year. Full data from the PIVOT-PO study will be presented at a future medical meeting.

Per Spero, around 2.9 million cases of cUTIs are treated annually in the United States alone. The current standard of care for cUTIs typically involves IV antibiotics, which require hospital administration. If approved, tebipenem HBr will be the first oral carbapenem antibiotic for cUTIs. An effective oral alternative would represent a major shift in the treatment paradigm, potentially reducing hospital stays, lowering costs and improving patient convenience.

SPRO Stock Performance

Year to date, shares of Spero have skyrocketed 128% against the industry’s 5% decline.

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More on SPRO’s Tebipenem

Tebipenem is being developed as part of a licensing agreement between Spero Therapeutics and GSK, signed in 2022. Per the terms, Spero is responsible for certain development work, including the PIVOT-PO study, while GSK holds exclusive rights to market the drug globally, except in certain Asian territories.

The drug has also been granted Qualified Infectious Disease Product (QIDP) and Fast Track designations from the FDA, which are intended to expedite development and review. QIDP status provides priority review and five additional years of market exclusivity upon approval, whereas Fast Track allows for more frequent FDA interaction and rolling submissions.

Notably, this is the second anti-infective program stopped early by GSK due to efficacy. Like tebipenem, GSK had also stopped the late-stage EAGLE 2 and 3 studies, which evaluated Blujepa (gepotidacin), an oral antibiotic for treating uncomplicated urinary tract infections (uUTIs). This drug was recently approved by the FDA for uUTIs.

SPRO’s Zacks Rank

Spero currently carries a Zacks Rank #4 (Sell).

Our Key Picks Among Biotech Stocks

A couple of better-ranked stocks from the industry are Adaptive Biotechnologies (ADPT - Free Report) and Agenus (AGEN - Free Report) , each carrying a Zacks Rank #2 (Buy) at present. You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.

In the past 60 days, estimates for Adaptive Biotechnologies’ 2025 loss per share have improved from 92 to 87 cents. During the same timeframe, estimates for 2026 loss per share have narrowed from 69 to 65 cents.

Adaptive Biotechnologies’ earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 21.38%. Shares of ADPT have surged 53% year to date.

Agenus’ loss per share estimate for 2025 has narrowed from $6.43 to $2.78 over the past 60 days, and the same for 2026 has improved from $6.57 to $5.26 during the same period.

Agenus’ earnings beat estimates in two of the trailing four quarters and missed the mark on the other two occasions, delivering an average negative surprise of 22.71%. Year to date, its shares have gained 10%.

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