On April 27, 2025 Nona Biosciences, a global biotechnology company providing integrated solutions from "Idea to IND" (I to ITM), reported that its partner, Pfizer, has presented preclinical data on PF-08052666 (HBM9033; SGN-MesoC2), a first-in-class topoisomerase 1 inhibitor (TOP1i)-based antibody-drug conjugate (ADC) targeting mesothelin (MSLN), at the AACR (Free AACR Whitepaper) Annual Meeting 2025 (Press release, Nona Biosciences, APR 27, 2025, View Source [SID1234652190]). This ADC was originally developed using Nona Biosciences’ proprietary Harbour Mice and integrated ADC platforms. Pfizer acquired its global clinical development and commercialization rights on December 14, 2023.

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Poster Presentation at AACR (Free AACR Whitepaper) Annual Meeting 2025

Title: PF-08052666 (HBM9033), a first-in-class topoisomerase 1 inhibitor-based ADC targeting MSLN, demonstrates potent antitumor activity in preclinical models of ovarian, lung, and colorectal cancers

Abstract Number: 324

Poster Board Number: 16

Session Title: Antireceptors and Other Biological Therapeutic Agents

Session Date: April 27, 2025

PF-08052666 was designed to address the limitations of earlier anti-MSLN ADCs through a novel antibody, differentiated linker-payload, and a higher drug-to-antibody ratio (DAR). It consists of a human IgG1 monoclonal antibody conjugated to a potent camptothecin-based TOP1i payload with a protease-cleavable linker, achieving an average DAR of 8.

Key Preclinical Findings Presented at AACR (Free AACR Whitepaper) Annual Meeting 2025

In vitro, PF-08052666 demonstrated direct cytotoxicity through delivery of payload to MSLN-positive cells, bystander killing activity on co-cultured MSLN-negative cells, and maintained cytotoxicity even in the presence of physiologically relevant concentrations of soluble MSLN.
In vivo, PF-08052666 outperformed a DM4-based anti-MSLN benchmark ADC in both cell-line and patient-derived xenograft models across multiple tumor types, including ovarian, lung, and colorectal cancers.
PF-08052666 also outperformed the DM4-based anti-MSLN benchmark ADC in heterogeneous xenograft models consisting of ad-mixed MSLN-positive and MSLN-negative cells, demonstrating the increased bystander activity of the novel linker-payload of MesoC2.
These promising preclinical results support the ongoing first-in-human phase 1 clinical trial of PF-08052666 in patients with advanced solid tumors (NCT06466187), which is currently enrolling participants.

"The preclinical data on PF-08052666 presented by Pfizer at AACR (Free AACR Whitepaper) 2025 reflects the strength of our technology platforms and our dedication to advancing transformative therapies," said Jingsong Wang, MD, PhD, Chairman of Nona Biosciences. "By leveraging our industry-leading technology platforms, we continue to drive innovation that enables the development of next-generation biotherapeutics. We look forward to further collaboration with Pfizer to accelerate breakthroughs that address critical medical needs."

About PF-08052666 (HBM9033)

PF-08052666 is an ADC drug that targets human MSLN, a tumor-associated antigen (TAA) upregulated in various solid tumors. The fully human monoclonal antibody (mAb) in PF-08052666 is derived from the Harbour Mice platform and possesses well-tuned properties, exhibiting reduced binding to soluble MSLN while maintaining strong binding and internalization to membrane-bound MSLN. The unique design of the mAb was created to enhance potency in various preclinical tumor models with differing MSLN expression levels, positioning PF-08052666 as a potential globally best-in-class therapeutic option.

On April 27, 2025 Merck (NYSE: MRK), known as MSD outside of the United States and Canada, reported results from the Phase 3 KEYNOTE-689 trial evaluating KEYTRUDA (pembrolizumab), Merck’s anti-PD-1 therapy, as a perioperative treatment regimen for patients with stage III or IVA, resected, locally advanced head and neck squamous cell carcinoma (LA-HNSCC) (Press release, Merck & Co, APR 27, 2025, View Source [SID1234652189]). Results at the first interim analysis of the trial showed KEYTRUDA significantly improved event-free survival (EFS) as part of a perioperative treatment regimen with adjuvant standard of care (SOC) radiotherapy with or without cisplatin compared to adjuvant standard of care (SOC) radiotherapy with or without cisplatin alone in patients with resectable LA-HNSCC. These data are being presented for the first time today during a Plenary Session at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting 2025 (Abstract #CT001) and were selected for the AACR (Free AACR Whitepaper) press program.

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After a median follow-up of 38.3 months (range, 9.0-66.5), treatment with KEYTRUDA before surgery (neoadjuvant), then continued in combination with standard of care radiotherapy (with or without cisplatin) after surgery followed by KEYTRUDA alone (adjuvant), reduced the risk of EFS events by 34% (HR=0.66 [95% CI, 0.49-0.88]; p=.0022) in the combined positive score (CPS) ≥10 population, by 30% (HR=0.70 [95% CI, 0.55-0.89; p=.0014) in the CPS ≥1 population and by 27% (HR=0.73 [95% CI 0.58-0.92]; p=.0041) in the intent-to-treat (ITT) population, compared to adjuvant radiotherapy (with or without cisplatin) alone in the ITT population. Among the CPS ≥10 population, median EFS was 59.7 months in the KEYTRUDA plus SOC group (95% CI, 41.1-not reached) versus 26.9 months (95% CI, 18.3-51.5) in the SOC group. Among the CPS ≥1 population, median EFS was 59.7 months (95% CI, 37.9-not reached) in the KEYTRUDA plus SOC group versus 29.6 months (95% CI, 19.5-41.9) in the SOC group. In the ITT population, median EFS was 51.8 months (95% CI, 37.5-not reached) in the KEYTRUDA plus SOC group versus 30.4 months (95% CI, 21.8-50.1) in the SOC group. The safety profile of KEYTRUDA was consistent with that observed in previously reported studies; no new safety signals were identified.

"As the first positive trial in over two decades for patients with resectable, locally advanced head and neck squamous cell carcinoma, the presentation of these landmark results marks an important moment for these patients and those who care for them," said Dr. Ravindra Uppaluri, the study’s co-principal investigator, director of Head and Neck Surgical Oncology, Brigham and Women’s Hospital and Dana-Farber Cancer Institute. "KEYNOTE-689 represents a meaningful development with a potential to provide an option that helps certain patients with LA-HNSCC reduce the risk of recurrence and disease progression earlier in their treatment journey."

"The addition of immunotherapy using KEYTRUDA to standard of care surgery and adjuvant (chemo)radiotherapy resulted in a significant reduction in the risk of event-free survival events by 27%, compared with standard of care therapy alone," said study co-principal investigator Dr. Douglas Adkins, Professor, Division of Oncology, Washington University School of Medicine in St. Louis. "These results are notable as they mark the first time an anti-PD-1 therapy has demonstrated a statistically significant and clinically meaningful improvement in event-free survival in the neoadjuvant and adjuvant setting in earlier stages of head and neck squamous cell carcinoma."

The study also showed a statistically significant improvement in major pathological response (mPR) rate, a key secondary endpoint, in patients with CPS ≥10 (difference in mPR rates: 13.7% [95% CI, 9.7-18.7]; p<0.00001), CPS ≥1 (9.8% [95% CI, 7.0-13.3]; p<0.00001) and in the ITT population (9.3% [95% CI, 6.7–12.8, P<.00001), compared to adjuvant radiotherapy alone.

A trend toward improvement in overall survival (OS), another key secondary endpoint, was observed in patients with CPS ≥10 (HR=0.72 [95% CI, 0.52-0.98]) at the time of this interim analysis for the KEYTRUDA plus standard of care regimen versus standard of care alone. The OS results did not reach statistical significance at the time of this interim analysis. Due to the statistical testing hierarchy, formal testing was not performed in the CPS ≥1 and ITT populations. OS will be evaluated at the next interim analysis.

"As the 12th positive pivotal trial for a KEYTRUDA-based regimen in earlier-stage cancers, the results from KEYNOTE-689 are a testament to our commitment to address an unmet need in this important area of research," said Dr. Marjorie Green, senior vice president and head of oncology, global clinical development, Merck Research Laboratories. "These compelling results illustrate the potential of this regimen to change the landscape of care for certain patients facing this challenging disease. We are working with the FDA and other global authorities to bring this new option to patients as quickly as possible."

A supplemental Biologics License Application (sBLA) for KEYTRUDA based on data from KEYNOTE-689 is under priority review with the U.S. Food and Drug Administration (FDA), with a Prescription Drug User Fee Act (PDUFA), or target action, date of June 23, 2025.

KEYTRUDA is currently approved as monotherapy and in combination regimens for appropriate patients with metastatic or unresectable, recurrent HNSCC in the U.S., Europe, China, Japan and other countries around the world. For more information, please see the "Selected KEYTRUDA (pembrolizumab) Indications in the U.S." section below.

Study design and additional data from KEYNOTE-689

KEYNOTE-689 is a randomized, active-controlled, open-label Phase 3 trial (ClinicalTrials.gov, NCT03765918) evaluating KEYTRUDA as neoadjuvant treatment and KEYTRUDA in combination with standard of care radiotherapy (with or without cisplatin) as adjuvant treatment in treatment-naïve patients with newly diagnosed, stage III or IVA resectable, locally advanced head and neck squamous cell carcinoma (LA-HNSCC). Efficacy outcomes are classified by programmed cell death ligand 1 (PD-L1) combined positive score (CPS) status. The primary endpoint is EFS, which is defined as the time from randomization to the first occurrence of radiographic disease progression; local or distant progression or recurrence; or death due to any cause. The secondary endpoints include OS, mPR, pathological complete response and safety. The study enrolled 714 patients who were randomized 1:1 to receive:

KEYTRUDA (200 mg intravenously [IV] every three weeks [Q3W] for two cycles) as neoadjuvant therapy prior to surgery, followed by either KEYTRUDA (200 mg IV Q3W for 15 cycles) plus standard of care radiotherapy with cisplatin (100 mg/m2 IV Q3W for three cycles) as adjuvant therapy following surgery for high-risk patients or KEYTRUDA (200 mg IV Q3W for 15 cycles) plus standard of care radiotherapy without cisplatin as adjuvant therapy following surgery for low-risk patients; or
No neoadjuvant therapy prior to surgery, followed by adjuvant standard of care radiotherapy with cisplatin (100 mg/m2 IV Q3W for three cycles) as adjuvant therapy following surgery for high-risk patients or standard of care radiotherapy without cisplatin as adjuvant therapy following surgery for low-risk patients.
The safety profile of KEYTRUDA was consistent with that observed in previously reported studies. Grade ≥3 treatment-related adverse events (TRAEs) occurred in 44.6% of patients receiving KEYTRUDA plus standard of care radiotherapy versus 42.9% of patients receiving standard of care radiotherapy alone. TRAEs led to death in 1.1% of patients receiving the KEYTRUDA regimen (n=4) and 0.3% of patients receiving standard of care radiotherapy (n=1). No new safety concerns were identified. Immune-mediated adverse events (AEs) of any grade occurred in 43.2% of patients receiving the KEYTRUDA regimen, most commonly hypothyroidism (24.7%).

About head and neck cancer

Head and neck cancer describes a number of different tumors that develop in or around the throat, larynx, nose, sinuses and mouth. Most head and neck cancers are squamous cell carcinomas that begin in the flat, squamous cells that make up the thin surface layer of the structures in the head and neck. Locally advanced head and neck squamous cell carcinoma (LA-HNSCC) is cancer that has grown outside the original location, but has not yet spread to distant parts of the body. There are several factors that greatly increase the risk of developing head and neck cancer, including tobacco and alcohol use and human papillomavirus (HPV). It is estimated there were more than 947,200 new cases of head and neck cancer diagnosed and over 482,400 deaths from the disease in 2022 globally. In the U.S., it is estimated there will be approximately 72,680 new cases of head and neck cancer diagnosed and more than 16,680 deaths from the disease in 2025.

On April 26, 2025 Pfizer Inc. (NYSE: PFE) reported results from the pivotal Phase 3 CREST trial of sasanlimab, an investigational anti-PD-1 monoclonal antibody (mAb), in combination with standard of care (SOC) Bacillus Calmette-Guérin (BCG) as induction therapy with or without maintenance in patients with BCG-naïve, high-risk non-muscle invasive bladder cancer (NMIBC) (Press release, Pfizer, APR 26, 2025, View Source [SID1234652209]). The trial met its primary endpoint of event-free survival (EFS) by investigator assessment, demonstrating a clinically meaningful and statistically significant improvement with sasanlimab in combination with BCG (induction and maintenance) as compared to BCG alone (induction and maintenance): Hazard Ratio (HR) of 0.68; 95% Confidence Interval (CI), 0.49-0.94; 2-sided p=0.019; median EFS not yet reached. These findings show a 32% reduction in risk of disease-related events, including high-grade disease recurrence or progression, with the sasanlimab combination regimen as compared with SOC treatment alone. Pre-specified subgroup analyses for patients harboring higher risk disease showed consistent benefit with EFS HR of 0.63 (0.41, 0.96) for T1 disease, and EFS HR 0.53 (0.29, 0.98) for those with CIS disease.

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EFS was a composite endpoint defined as the time from randomization to the earliest of recurrence of high-grade disease, progression of disease, persistence of carcinoma in situ (CIS), or death due to any cause. The probability of being event-free at 36 months was 82.1% (95% CI, 77.4-85.9) with sasanlimab in combination with BCG (induction and maintenance), and 74.8% (95% CI, 69.7-79.2) with BCG alone (induction and maintenance). Results from the CREST trial are being presented today in a plenary oral presentation at the 2025 American Urological Association (AUA) Annual Meeting.

"New bladder cancer treatment options that help reduce rates of disease recurrence or progression are long overdue. Up to 50% of patients with high-risk non-muscle invasive bladder cancer may experience failure of BCG intravesical immunotherapy, yet it has been the standard of care after tumor resection for decades," said Neal Shore, M.D., FACS, Medical Director for START Carolina Research Center, and lead investigator for the CREST trial. "These Phase 3 results show that combining sasanlimab with BCG induction and maintenance therapy earlier in the course of the disease significantly prolonged event-free survival, highlighting the value and potential of sasanlimab in combination with BCG to redefine the treatment paradigm and reduce the burden for patients."

As the ninth most common cancer worldwide, bladder cancer accounts for up to 220,000 deaths annually.1,2 NMIBC, in particular, represents approximately 75% of all bladder cancer cases.3 In the U.S., it is estimated that about 38,000 people have high-risk NMIBC.4 While BCG treatment has been shown to reduce the risk of tumor recurrence, approximately 40-50% of patients with high-risk NMIBC receiving BCG will eventually have disease recurrence or progression despite therapy.5-7

"Today’s pivotal Phase 3 CREST results offer a much-needed therapeutic breakthrough and spotlight sasanlimab as the first immunotherapy combination with BCG to significantly improve outcomes for patients with BCG-naïve, high-risk NMIBC in over three decades," said Megan O’Meara, M.D., Interim Chief Development Officer, Pfizer Oncology. "The CREST findings are especially impactful for these patients with early-stage cancer who may benefit the most from innovative treatment regimens, including a subcutaneous immune checkpoint inhibitor, that delay disease recurrence or progression. These results underscore our long-standing commitment to patients with bladder cancer across all stages of the disease. We look forward to working with global regulatory authorities to potentially bring sasanlimab as an important new treatment option to patients with high-risk NMIBC."

Sasanlimab in combination with BCG (induction only) did not result in prolongation of EFS when compared to BCG alone (induction and maintenance), a key secondary endpoint: HR of 1.16; 95% CI, 0.87-1.55; 2-sided p=0.312, underscoring the need for BCG maintenance not only as a component of SOC treatment but also in combination with sasanlimab. Early interim analysis for the key secondary overall survival (OS) endpoint suggested no difference between treatment arms, with a median follow-up of 40.9 months. The study continues for survival follow-up until the final analysis. Complete response (CR) and duration of CR were additional secondary endpoints for patients with CIS at randomization. The CR rate achieved at any time was 89.8% with sasanlimab in combination with BCG (induction and maintenance) and 85.2% with BCG alone (induction and maintenance). Notably, for those patients with CIS at randomization who achieved a CR, the probability of remaining in CR at 36 months was 91.7% with sasanlimab in combination with BCG (induction and maintenance) compared to 67.7% with BCG alone (induction and maintenance).

The overall safety profile of sasanlimab in combination with BCG was generally consistent with the known profile of BCG and data reported from clinical trials with sasanlimab. The profile of sasanlimab was also generally consistent with the reported safety profile of PD-1 inhibitors. Pfizer has shared these data with global health authorities to support potential regulatory filings.

About CREST

The CREST trial is a Phase 3, multinational, randomized, open-label, three parallel-arm study of sasanlimab, an anti-PD-1 mAb, in combination with BCG (BCG induction with or without BCG maintenance) versus BCG (induction and maintenance) in participants with BCG-naïve, high-risk NMIBC. Patients were randomized to receive sasanlimab 300 mg by subcutaneous (SC) injection every four weeks up to cycle 25 (cycle = four weeks), in combination with BCG once weekly for six consecutive weeks (induction period) followed (Arm A; n=352) or not (Arm B; n=352) by maintenance with BCG, or BCG induction and maintenance up to cycle 25 (Arm C; n=351). The primary endpoint is EFS as assessed by the investigator, between Arm A and C, defined as a composite endpoint that combines time from randomization to the earliest of recurrence of high-grade disease, progression of disease, persistence of CIS, or death. Key secondary endpoints include EFS as assessed by the investigator between Arm B and Arm C, between Arms A/B and Arm C. In patients with CIS, CR and duration of CR were secondary endpoints. For more information on the CREST trial (NCT04165317), go to www.clinicaltrials.gov.

About Sasanlimab

Sasanlimab is a humanized immunoglobulin G4 (IgG4) mAb that binds to human PD-1 to block its interaction with PD-1 and PD-L1/PD-L2. PD-1 is a protein expressed on T cells, dendritic cells, natural killer cells, macrophages, and B cells, that functions as an immune checkpoint that negatively regulates T-cell activation and effector function when activated by its ligands and may play an important role in tumor evasion from host immunity. It can be administered through a once every four weeks SC injection by prefilled syringe (2mL).

In early-stage clinical studies, sasanlimab administered at 300 mg SC every four weeks showed clinical efficacy in advanced solid tumors and advanced urothelial cancer. In addition to NMIBC, sasanlimab is being evaluated in several ongoing clinical trials in combination with Pfizer’s antibody drug conjugate (ADC) portfolio.

On April 26, 2025 UroGen Pharma Ltd. (Nasdaq: URGN), a biotech company dedicated to developing and commercializing innovative solutions that treat urothelial and specialty cancers, reported an updated 18-month DOR of 80.6% (95% CI: 74.0, 85.7), by Kaplan-Meier estimate, from the Phase 3 ENVISION trial of UGN-102 (mitomycin) for intravesical solution, an investigational treatment for recurrent LG-IR-NMIBC (Press release, UroGen Pharma, APR 26, 2025, View Source [SID1234652195]). These data were featured today in an Oral Presentation Session (Abstract ID: PD12) at the AUA 2025 Annual Meeting in Las Vegas, Nevada.

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"This new update from the pivotal ENVISION trial of UGN-102 demonstrated a compelling probability of remaining in complete response of 80.6% at 18 months in patients who achieved a complete response (CR) at three months (79.6%)," said Sandip Prasad M.D., M.Phil., Director of Genitourinary Surgical Oncology, Vice Chair of Urology at Morristown Medical Center/Atlantic Health System, NJ, and Principal Investigator of the ENVISION trial. "Low-grade bladder cancer is a persistent cancer that frequently recurs and comes with its own risks. There is a significant unmet need in finding treatment options for patients with recurrent low-grade bladder cancer."

The existing standard of care for LG-IR-NMIBC is an invasive surgical procedure requiring anesthesia called transurethral resection of bladder tumor (TURBT). Repeated TURBT procedures can impact patients’ physical health and quality of life and are even associated with an increased risk in mortality. Due to high recurrence rates, LG-IR-NMIBC patients, who are typically elderly with comorbidities, will likely need multiple TURBTs under general anesthesia over the course of their lifetime. An estimated 59,000 patients with LG-IR-NMIBC recur annually and face the burden and risks of repeat surgeries that often provide limited value.

Mark Schoenberg, M.D., Chief Medical Officer of UroGen, stated, "The duration of response data from the ENVISION trial further underscores UGN-102’s potential to positively impact the treatment landscape for patients with recurrent LG-IR-NMIBC. Many of these patients are elderly and face the burden of repeated surgeries under general anesthesia, highlighting the urgent need for innovative treatment options. If approved, we believe UGN-102’s potential to deliver durable complete responses, reduce recurrence rates, and extend treatment-free intervals would represent a significant advancement in the management of recurrent LG-IR-NMIBC."

The most common treatment-emergent adverse events (TEAEs) in the ENVISION trial were dysuria, hematuria, urinary tract infection, pollakiuria, fatigue, and urinary retention. The TEAEs were typically mild-to-moderate in severity and either resolved or were resolving. The ENVISION trial demonstrated a similar safety profile to that observed in other studies of UGN‑102. Median follow-up time at 18 months was 18.7 months after the three-month CR.

UroGen completed the submission of a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for UGN-102 as a treatment for LG-IR-NMIBC ahead of schedule, and the FDA accepted the NDA for UGN-102 with a Prescription Drug User Free Act (PDUFA) goal date of June 13, 2025.

About UGN-102

UGN-102 (mitomycin) for intravesical solution is an innovative drug formulation of mitomycin, currently in Phase 3 development for the treatment of recurrent LG-IR-NMIBC. Utilizing UroGen’s proprietary RTGel technology, a sustained release, hydrogel-based formulation, UGN-102 is designed to enable longer exposure of bladder tissue to mitomycin, thereby enabling the treatment of tumors by non-surgical means. UGN-102 is delivered to patients using a standard urinary catheter in an outpatient setting by a trained healthcare professional. UroGen completed the submission of the rolling NDA for UGN-102 in August 2024, ahead of schedule. The FDA accepted the NDA for UGN-102 and assigned a PDUFA goal date of June 13, 2025.

About Non-Muscle Invasive Bladder Cancer (NMIBC)

LG-IR-NMIBC affects around 82,000 people in the U.S. every year and of those, an estimated 59,000 are recurrent. Bladder cancer primarily affects older populations with increased risk of comorbidities, with the median age of diagnosis being 73 years. Guideline recommendations for the management of NMIBC include TURBT as the standard of care. Up to 70 percent of NMIBC patients experience at least one recurrence and LG-IR-NMIBC patients are even more likely to recur and face repeated TURBT procedures.

About ENVISION

The Phase 3 ENVISION trial is a single-arm, multinational, multicenter pivotal study evaluating the efficacy and safety of UGN-102 (mitomycin) for intravesical solution as a chemoablative therapy in patients with LG-IR-NMIBC. The Phase 3 ENVISION trial completed target enrollment with 240 patients across 56 sites. Study participants received six once-weekly intravesical instillations of UGN-102. The primary endpoint evaluated the CR rate at the three-month assessment after the first instillation, and the key secondary endpoint evaluated durability over time in patients who achieved a CR at the three-month assessment. Learn more about the Phase 3 ENVISION trial at www.clinicaltrials.gov (NCT05243550).

On April 26, 2025 UroGen Pharma Ltd. (Nasdaq: URGN), a biotech company dedicated to developing and commercializing innovative solutions that treat urothelial and specialty cancers, reported encouraging safety data from the Phase 1 dose-escalation study for UGN-301 (zalifrelimab) intravesical solution, an investigational drug in development for the treatment of recurrent non-muscle invasive bladder cancer (NMIBC) (Press release, UroGen Pharma, APR 26, 2025, View Source [SID1234652194]).

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"The early safety profile and clinical activity results from this study are encouraging," said Jay Raman, M.D., Professor and Chair of Urology, and Professor of Surgery, Penn State Cancer Institute, PA. "This innovative approach of localized drug delivery combined with immune modulation merits additional investigation in the treatment of non-muscle invasive bladder cancer."

The multi-part clinical study included up to 30 patients per arm, aimed to assess safety and determine the recommended Phase 2 dose of UGN-301 as monotherapy and in combination with other agents. In the monotherapy arm, dose escalation continued to the maximum feasible dose. No dose-limiting toxicities and no treatment-emergent adverse events leading to treatment discontinuation were observed. This study also demonstrated that local delivery of UGN-301 formulated in our proprietary reverse thermal gel (RTGel) allowed sustained exposure of zalifrelimab in the bladder with limited systemic exposure, which mitigated the risk of systemic immune-related toxicities associated with CTLA-4 inhibition.

With respect to clinical activity observed in the trial, among evaluable patients who received UGN-301, 46% (6 of 13) of those with Ta/T1 disease and 33% (2 of 6) of those with carcinoma in situ (CIS) ± Ta/T1 disease were recurrence-free or had achieved a complete response at week 12. Notably, 60% (3 of 5) of patients with Ta/T1 disease treated with 300 mg continued to remain recurrence-free at the 15-month disease assessment, including one patient with high-grade T1 disease. In the 500 mg cohort, 25% (1 of 4) of patients with CIS disease and 33% (1 of 3) of patients with Ta/T1 disease remained disease-free at six months, both of whom are still active participants in the study.

These findings highlight the potential of UGN-301 as a targeted treatment for NMIBC with an acceptable safety profile. Presentation of data from the combination arms is planned for later this year.

"Our hypothesis is that UGN-301’s unique formulation could potentially offer the dual benefits of maximizing therapeutic activity while minimizing systemic side effects, a key challenge in cancer immunotherapy," said Mark Schoenberg, Chief Medical Officer, UroGen. "Although this requires additional clinical investigation, we are encouraged by the potential of UGN-301 as an investigational treatment for patients with recurrent NMIBC."

About Non-Muscle Invasive Bladder Cancer and High-Grade Disease

In the U.S., bladder cancer is the second most common urologic cancer in men. Bladder cancer primarily affects older populations with increased risk of comorbidities, with the median age of diagnosis being 73 years. High-grade non-muscle invasive bladder cancer (HG-NMIBC) is a serious and potentially life-threatening form of bladder cancer that remains confined to the inner layers of the bladder wall but exhibits aggressive behavior and a higher risk of progression. In the U.S., HG-NMIBC accounts for approximately 30–40% of all newly diagnosed NMIBC cases. Patients with HG-NMIBC face a significantly elevated risk of recurrence and progression to muscle-invasive disease, necessitating close surveillance and aggressive treatment. The standard of care includes complete transurethral resection of bladder tumor, often followed by intravesical therapy such as Bacillus Calmette-Guérin (BCG). However, BCG has a treatment failure rate of approximately 40-50%, leaving patients with limited treatment options short of radical cystectomy. Given the high recurrence and progression rates, HG-NMIBC presents a substantial clinical and quality-of-life burden. Upon recurrence, which occurs in approximately 70% of patients, the patients undergo another round of BCG therapy with a response rate of approximately 30%.

About UGN-301

UGN-301 is an anti-CTLA-4 monoclonal antibody (zalifrelimab), originally licensed from Agenus Inc. in 2019. It is formulated with RTGel, our proprietary reverse-thermal hydrogel, for intravesical administration into the bladder. Intravesical administration of UGN-301 is designed to increase drug concentrations in the bladder without significant systemic exposure, potentially diminishing the systemic toxicity associated with CTLA-4 blockade. UroGen is evaluating UGN-301 in a multi-arm Phase 1 study of UGN-301 as monotherapy and in combination with other agents. The safety of UGN-301 is being evaluated in the monotherapy arm of the study as combination therapy for HG-NMIBC.