RiboX Therapeutics Receives FDA RMAT Designation for RXRG001 in Radiation-Induced Xerostomia
RiboX Therapeutics, a clinical-stage biotechnology company focused on discovering and developing fully engineered circular RNA (circRNA) therapeutics, announced that the U.S. Food and Drug Administration (FDA) has granted Regenerative Medicine Advanced Therapy (RMAT) designation to RXRG001 for the treatment of radiation-induced xerostomia (RIX) and hyposalivation. The designation represents an important regulatory milestone for the company as it advances its investigational circular RNA therapy for patients whose salivary gland function has been damaged by radiation treatment.
The FDA granted the RMAT designation based on preliminary clinical evidence generated through the ongoing Phase 1/2a SPRINX-1 clinical study. The trial is evaluating RXRG001 in adults experiencing radiation-induced xerostomia and hyposalivation following treatment for head and neck cancer.
Radiation-induced damage to the salivary glands can lead to persistent reductions in saliva production. The resulting dry-mouth condition can affect eating, swallowing, speaking, oral health and overall quality of life. Current approaches are largely focused on managing symptoms rather than restoring the underlying function of salivary glands. RiboX is developing RXRG001 with the goal of addressing this underlying impairment through localized delivery of a therapeutic circular RNA designed to promote production of a protein involved in water transport.
RXRG001 Advances in Phase 1/2a Development
RXRG001 is currently being studied in a first-in-human, multicenter Phase 1/2a clinical trial in the United States. The SPRINX-1 study is designed to assess the safety and tolerability of RXRG001 while also generating preliminary evidence regarding its potential efficacy.
The ongoing dose-escalation study evaluates intraductal administration of RXRG001 directly into the parotid glands. This localized delivery approach is intended to place the investigational therapy at the site where restoration of salivary gland function is needed.
The trial is evaluating adults with radiation-induced xerostomia and hyposalivation. By studying patients whose salivary glands have been affected by previous radiation therapy, RiboX aims to determine whether RXRG001 can potentially improve the biological mechanisms associated with saliva production.
The preliminary clinical evidence generated by SPRINX-1 provided the basis for the FDA’s RMAT designation. Although the study remains ongoing, the regulatory recognition provides an opportunity for RiboX to engage with the FDA more closely as the company develops RXRG001 and plans subsequent clinical development.
RXRG001 previously received FDA Fast Track designation, giving the program an additional regulatory pathway intended to facilitate development of therapies addressing serious conditions where there is an unmet medical need.
Circular RNA Approach
At the heart of RXRG001 is RiboX’s proprietary circular RNA technology platform. Unlike conventional linear RNA molecules, circular RNA molecules form a closed-loop structure. RiboX is applying this technology to the development of engineered therapeutics intended to enable sustained or controlled production of therapeutic proteins.
RXRG001 is a proprietary circular RNA therapeutic designed to encode human aquaporin-1, or hAQP1. Aquaporin-1 is a water-channel protein that plays a role in transporting water across cell membranes and is involved in fluid movement in biological tissues.
The investigational therapy combines the circular RNA molecule with a lipid nanoparticle (LNP) delivery system. The LNP is designed to facilitate delivery of the therapeutic RNA to target cells following administration.
For RXRG001, RiboX is using local administration into the salivary glands. Once delivered, the circular RNA is designed to enable expression of functional hAQP1. The company’s therapeutic strategy is based on the potential for hAQP1 expression to support water transport within damaged salivary gland tissue and ultimately contribute to restoration of saliva production.
This approach represents a regenerative medicine strategy rather than simply treating the symptoms associated with dry mouth. By targeting a biological mechanism involved in fluid transport, RiboX is investigating whether its therapy can help restore function in salivary glands that have been compromised by radiation treatment.
Addressing an Unmet Need in Head and Neck Cancer Survivors
Radiation therapy is an important treatment option for many patients with head and neck cancers. However, radiation exposure can damage healthy tissues located near tumors, including the salivary glands. When the glands are unable to produce sufficient saliva, patients can experience chronic xerostomia and hyposalivation.
The effects can extend beyond discomfort. Saliva contributes to lubrication of the mouth, swallowing, digestion and protection of oral tissues. Reduced saliva production may therefore create challenges with eating and speaking and can contribute to oral health problems.
For patients who have completed cancer treatment, persistent radiation-induced xerostomia can become a long-term complication that affects daily life. Existing treatment approaches may include measures intended to stimulate remaining salivary function, replace moisture or alleviate symptoms. However, these approaches do not necessarily restore the damaged glandular tissue or its normal biological function.
RiboX is therefore investigating RXRG001 as a potential therapeutic approach that could address the underlying impairment.
“The FDA’s RMAT designation for RXRG001 represents an important milestone for RiboX and recognizes the promising preliminary clinical evidence generated with our circular RNA platform,” said Weiyi Zhang, Ph.D., Co-Founder and Chief Executive Officer of RiboX.
Zhang noted that radiation-induced xerostomia and hyposalivation can have a substantial impact on patients following head and neck cancer treatment. He also highlighted the limitations of current treatment options, which primarily focus on managing symptoms.
“We look forward to working closely with FDA as we advance RXRG001 and evaluate its potential to restore salivary gland function for these patients,” Zhang added.
Significance of the RMAT Designation
The RMAT designation is an FDA program intended to support the development and review of regenerative medicine therapies for serious or life-threatening diseases and conditions.
To qualify for RMAT designation, a therapy must have preliminary clinical evidence indicating its potential to address an unmet medical need. The designation can provide sponsors with opportunities for earlier and enhanced interactions with the FDA throughout the development process.
For RiboX, the designation could facilitate regulatory discussions related to RXRG001’s development program. The FDA may provide intensive guidance regarding efficient clinical development and regulatory strategies, helping sponsors address development questions as they move toward later-stage studies.
The designation may also provide opportunities to discuss potential approaches for accelerating development and review, depending on the characteristics of the program and the clinical evidence generated during development.
Importantly, RMAT designation does not represent FDA approval and does not establish that RXRG001 has been proven safe or effective. The investigational therapy must continue through clinical development and regulatory evaluation to determine whether its potential benefits outweigh its risks.
Building on Fast Track Designation
The RMAT designation adds to the regulatory recognition already received by RXRG001. The therapy previously received FDA Fast Track designation, another program intended to facilitate the development of treatments for serious conditions where existing therapies may not adequately address patient needs.
Together, the designations provide RiboX with additional opportunities for regulatory interaction as it continues to evaluate RXRG001.
The company’s immediate focus remains the ongoing SPRINX-1 Phase 1/2a study. The study is generating information on safety, tolerability and preliminary efficacy following direct administration of RXRG001 into the parotid gland ducts.
As the dose-escalation portion progresses, clinical findings will help inform the future development strategy for the program. Additional clinical research will ultimately be needed to establish the therapy’s efficacy, determine its safety profile and assess the durability of any potential improvements in salivary gland function.
Potential of Regenerative RNA Therapy
The development of RXRG001 highlights the expanding application of RNA technologies beyond traditional approaches. While RNA-based medicines have gained significant attention across multiple therapeutic areas, RiboX is applying engineered circular RNA technology to regenerative medicine.
The company’s strategy combines circRNA technology, LNP delivery and localized administration to target a specific tissue affected by radiation damage. If successful, the approach could demonstrate the potential of RNA therapeutics to support the restoration of biological functions rather than focusing solely on symptom relief.
For patients living with persistent radiation-induced xerostomia and hyposalivation, an approach capable of improving salivary gland function could represent a meaningful advance.
The RMAT designation gives RiboX an opportunity to work closely with the FDA while continuing to generate clinical evidence. As the SPRINX-1 study advances, future results will be important in determining whether RXRG001 can translate its proposed biological mechanism into meaningful clinical benefits for patients.
With RXRG001 now holding both RMAT and Fast Track designations, RiboX is positioned to continue advancing its clinical-stage program and its broader circular RNA platform. The company’s work reflects an effort to develop innovative regenerative therapies for conditions in which conventional symptom-management approaches may not adequately address the underlying tissue damage.
The ongoing clinical development of RXRG001 will ultimately determine its safety, efficacy and potential role in treating radiation-induced xerostomia and hyposalivation. For now, the FDA’s RMAT designation represents a significant milestone for RiboX and provides additional regulatory support as the company moves forward with its investigation of circular RNA-based regenerative medicine.
About Radiation-Induced Xerostomia (RIX) and Hyposalivation
RIX and hyposalivation are common and potentially debilitating complications of radiation therapy for head and neck cancers. Radiation can cause lasting damage to the salivary glands, resulting in reduced saliva production and persistent dry mouth. These conditions can significantly affect patients’ ability to eat, chew, swallow and speak, contribute to oral and dental complications, and negatively impact quality of life. Current treatment approaches are primarily focused on symptom management, highlighting the need for therapies that can restore salivary gland function.
About RXRG001
RXRG001 is an investigational circular RNA therapeutic designed to restore salivary gland function in patients with radiation-induced xerostomia and hyposalivation. RXRG001 consists of circular RNA encoding human aquaporin-1 encapsulated in lipid nanoparticles and is administered directly into the salivary glands. By enabling local expression of hAQP1, RXRG001 is designed to restore fluid transport and saliva secretion in radiation-damaged salivary glands. RXRG001 is currently being evaluated in SPRINX-1 (NCT06714253), a Phase 1/2a clinical study evaluating its safety, tolerability and preliminary efficacy in adults with RIX and hyposalivation.
About RiboX Therapeutics
RiboX is a clinical-stage biotechnology company pioneering the discovery and development of fully engineered circular RNA therapeutics to address unmet medical needs across a broad range of diseases. The company’s proprietary circular RNA technology and delivery platforms are designed to enable durable protein expression and unlock the therapeutic potential of RNA medicines. For more information, visit www.riboxtx.com.