Study did not meet the primary or key secondary endpoint

45% reduction in hypoglycemia events observed at top ersodetug dose (10 mg/kg) compared to 40% improvement in placebo arm

Management to host conference call today at 8:30am ET

REDWOOD CITY, Calif., Dec. 11, 2025 (GLOBE NEWSWIRE) -- Rezolute, Inc. (NASDAQ:RZLT) ("Rezolute" or the "Company"), a late-stage rare disease company focused on treating hypoglycemia caused by hyperinsulinism, today announced topline results from its Phase 3 sunRIZE study evaluating ersodetug in patients with congenital hyperinsulinism (HI).

The study did not meet its primary endpoint, which assessed change in the average weekly hypoglycemia events by self monitored blood glucose. There was an approximate 45% reduction in hypoglycemia events observed at the top ersodetug dose (10 mg/kg), which was not statistically significant compared to the placebo group, which experienced a 40% improvement. Furthermore, the study did not meet its key secondary endpoint, which assessed change in average daily percent time in hypoglycemia by continuous glucose monitoring (CGM). At the 10 mg/kg dose of ersodetug, an approximate 25% reduction in time in hypoglycemia was observed, which was not statistically significant compared to the placebo, which increased by approximately 5%.

At the study dose regimens of 5 and 10 mg/kg administered every other week for 3 doses, followed by every 4 weeks over the remainder of the 24-week treatment duration, ersodetug target drug concentrations were achieved, across all age groups studied.

Safety observations from the study were generally favorable and, in the opinion of the Company, support safe use of ersodetug in pediatric and adult patients. Two of the study participants experienced serious hypersensitivity reactions which led to early discontinuation of study drug. The incidence of serious allergic reactions across the program is relatively low compared to biologic or monoclonal antibody treatments. The most commonly reported study adverse event in ersodetug treated participants compared to placebo was hypertrichosis, which was generally mild and self-limiting.

"We are disappointed that the study did not demonstrate significant improvements in glucose-related endpoints relative to placebo as well as for the patients and families living with congenital HI who urgently need new treatment options," said Brian Roberts, M.D., Chief Medical Officer of Rezolute. "At the same time, there are aspects of the results that merit additional investigation, and we are conducting a thorough evaluation to gain a better understanding of the study outcomes, which will inform our path forward. We intend to meet with FDA under our Breakthrough Therapy Designation to consider next steps for the program. We are deeply grateful to the patients and families, the majority of whom have continued into the open label extension part of the study, as well as to the investigators and site teams who participated in this important study."

The Phase 3 upLIFT study for tumor HI is ongoing with topline results expected in the second half of 2026.

Conference Call Information

To access the event by phone, please dial 1-877-317-6789 from the U.S. and Canada or 1-412-317-6789 internationally and ask to be joined into the Rezolute call. The live webcast can be accessed on the investor page of Rezolute's website at https://ir.rezolutebio.com.

About sunRIZE

The Phase 3 sunRIZE study (RZ358-301) is a multi-center, randomized, double-blind, placebo-controlled, parallel arm study designed to evaluate the efficacy and safety of ersodetug in patients with congenital hyperinsulinism (HI), ages 3 months to 45 years old, who are experiencing continued hypoglycemia on currently available standard of care (SOC). Eligible participants are randomized to one of three treatment arms to receive either ersodetug (5 or 10 mg/kg) or matched placebo-control as add on to existing SOC. Study drug is administered every other week during an initial loading phase, and then every 4 weeks during the 6-month controlled pivotal treatment period. Following the pivotal treatment phase of the study, participants may roll-over into an optional open-label extension phase to continue to receive ersodetug.

The study enrolled 63 participants in more than a dozen countries around the world, inclusive of U.S. patients. The primary and key secondary efficacy endpoints in the study are the change from baseline in the average number of hypoglycemia events per week and the average percent time in hypoglycemia, respectively, over six months of treatment.

About Ersodetug

Ersodetug is a fully human monoclonal antibody that binds allosterically to the insulin receptor to decrease receptor over-activation by insulin and related substances (such as IGF-2) in the setting of hyperinsulinism (HI), thereby improving hypoglycemia. Because ersodetug acts downstream from the pancreas, it has the potential to be universally effective at treating hypoglycemia due to any congenital or acquired form of HI.

About Rezolute, Inc.

Rezolute is a late-stage rare disease company focused on treating hypoglycemia caused by hyperinsulinism (HI). The Company's antibody therapy, ersodetug, is designed to treat all forms of HI and has shown meaningful benefit in clinical trials and real-world use. For more information, visit www.rezolutebio.com.

Forward-Looking Statements

This release, like many written and oral communications presented by Rezolute and our authorized officers, may contain certain forward-looking statements regarding our prospective performance and strategies within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended. We intend such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995 and are including this statement for purposes of said safe harbor provisions. Forward-looking statements, which are based on certain assumptions and describe future plans, strategies, and expectations of Rezolute, are generally identified by use of words such as "anticipate," "believe," "estimate," "expect," "intend," "plan," "project," "seek," "strive," "try," or future or conditional verbs such as "could," "may," "should," "will," "would," or similar expressions. These forward-looking statements include, but are not limited to the timing of future actions that we could take following the release of topline data, or the timing of the release of topline results from the upLIFT study. Our ability to predict results or the actual effects of our plans or strategies is inherently uncertain. Accordingly, actual results may differ materially from anticipated results. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release. Except as required by applicable law or regulation, Rezolute undertakes no obligation to update these forward-looking statements to reflect events or circumstances that occur after the date on which such statements were made. Important factors that may cause such a difference include any other factors discussed in our filings with the SEC, including the Risk Factors contained in the Rezolute's Annual Report on Form 10-K and Quarterly Reports on Form 10-Q, which are available at the SEC's website at www.sec.gov. You are urged to consider these factors carefully in evaluating the forward-looking statements in this release and are cautioned not to place undue reliance on such forward-looking statements, which are qualified in their entirety by this cautionary statement.

Rezolute Contacts:

Christen Baglaneas

cbaglaneas@rezolutebio.com

508-272-6717

Carrie McKim

cmckim@rezolutebio.com

336-608-9706

Rezolute Announces Phase 3 sunRIZE Study Results in Congenital Hyperinsulinism