Plus Therapeutics (NASDAQ: PSTV) is a pharmaceutical company engaged in the development of targeted therapies for difficult-to-treat cancers. Currently, it is moving forward with a pipeline of product candidates with lead programs for periolar metastasis and recurrent glioblastoma. Email conversation with Alpha StreetDr. Marc Hedrick, CEO of Plus Therapeutics, provided insights into the company’s strategic vision and the possibilities of transforming oncological treatments.
Can you provide a brief overview of Plus Therapeutics and its clinical programs?
In addition to being described in the NASDAQ under the ticker symbol PSTV, Therapeutics is a clinical stage pharmaceutical company that develops targeted radiation therapy designed to deliver safe and effective radiation directly to the tumor for adults and children with rare and difficult to treat cancers. We are based in the US, headquartered in Houston. Our lead radiation therapy, Reyobiq, is specifically prescribed to treat central nervous system (CNS) cancer. There are three Leyovik clinical trial programs: periocranial metastasis (LM), recurrent glioblastoma (GBM), and pediatric brain cancer (PBC).
The company’s three trials are supported by grants from NIH, DOD and CPRIT. The first trial, Respect-GBM, is due to a recurring GBM and is expected to close Phase 2 registration soon. GBM is a fatal, treatment-resistant malignant brain tumor that affects approximately 10,000 people each year. The second exam, respect lm, is for LM. Our Phase 2 exam is currently registered. LM is a late-stage cancer complication in which cancer cells spread from many primary cancers such as the breast, lung, melanoma, and gastrointestinal cells spread to the CNS, affecting about 150,000 people each year, but recent studies have shown that the actual instances are much higher. Our PBC trial, Respect-PBC, is looking forward to registering soon. PBCs such as high-grade gliomas and exomatous are malignant tumors of the brain or spinal cord, which account for approximately 26% of all childhood cancers.
Phase 1 clinical trials in GBM and LM show strong signs of safety and efficacy of Reyobiq. Data show that high radiation doses are locally delivered normally to the tumor, with no significant safety issues and are well tolerated. The findings provided evidence of improved long-term survival and patient outcomes. Additionally, the US FDA allows Reyobiq’s high-speed truck and orphan drug designation, highlighting the regulatory support we have.
Additionally, Therapeutics also has CNSide Diagnostics, a direct subsidiary that provides the CNSide CSF assay platform. CN Side is a highly sensitive cerebrospinal fluid-based assay platform used for detection, quantification and characterization of tumor cells in cancer and melanoma LM patients. It is the first and only diagnostic platform commercially available in the US
What are the unique benefits of Plus Therapeutics’ targeted radiation therapy program over existing or emerging treatments in this field?
Radiation therapy is an important treatment for cancer and serves as the gold standard for fighting CNS cancer. However, traditional external beam radiation therapy (EBRT) is limited by low doses to minimize potential damage to healthy tissues and organs and the need for frequent treatment sessions over several weeks. These are inconvenient and time-consuming for patients. EBRT is associated with a variety of complications, including loss of taste, hair loss, skin changes, and other adverse effects caused by toxic radiation levels within the body.
What makes Plus Plus Therapeutics different is that they developed targeted radiation therapy to address these limitations with EBRT. Additionally, targeted radiation therapy for therapeutic agents is internal radiation therapy that locally delivers radiation to the tumor via catheter injection or injection into the tumor space. This approach reduces the risk of radiation damage to surrounding healthy tissues and organs, resulting in radiation near or to the tumor.
Compared to EBRT, our Reyobiq product candidates allow us to deliver 15-20 times more accurate radiation doses directly to the tumor in one patient visit.
What are the main challenges when bringing Reyobiq to the market? And how do you see the evolution of your own radiation therapy platform over the next five years?
One of the challenges is that we are focusing on rarer and more difficult to treat cancers. This means it can be difficult to find a patient to participate in clinical trials. We are overcoming this challenge by establishing new clinical trial sites in more major U.S. cities, thereby improving patient access. Another challenge is to ensure that radiation therapy can be guided to the right patients at the right time. However, this problem is alleviated by establishing a robust supply chain for drug production and transportation.
While passing the FDA approval process is a challenge, we are on track to generate compelling clinical data for GBM and LM, leveraging FDA designations, and seeking accelerated approval to bring radiation therapy to patients with few treatment options. Over the next five years, we plan to expand our Reyobiq portfolio to non-CNS cancers.
Beyond GBM, LM, and PBC, what other pipeline candidates are you actively exploring?
In the case of Reyobiq, we are conducting preclinical studies evaluating the combination of targeted therapies and immune checkpoint inhibitors. Additionally, preclinical data have been published for several other indications, including peritoneal carcinoma, head and neck cancer, and breast cancer. This will serve as the basis for future FDA Ind approvals. In addition to Reyobiq, there is also rhenium-based radioembolic therapy in preclinical development for the treatment of primary and secondary liver cancers.
Primary liver cancer, or hepatocellular carcinoma (HCC), occurs most frequently in people with chronic liver disease, including fatty liver disease and cirrhosis as the optimal risk factor, affecting approximately 42K individuals each year. Secondary liver cancer, or metastatic colorectal cancer (MCRC), is a progressive IV cancer that spreads from the colon or rectum to the liver and affects approximately 75K people each year. Our next-generation radiation embolism therapy is designed for injections of biodegradable microspheres and direct high-dose radiation into the hepatic artery, blocking tumor blood flow and reducing tumors. Therapy is expected to minimize radiation exposure to normal tissues and improve patient survival expectations and quality of life.
Given the positive data from Reyobiq clinical trials, what milestones do the therapeutics and drugs achieve in the short term?
Reyobiq’s Respect GBM Phase 2 Clinical Trials will be completed soon. LM’s Respectful LM Multidose Clinical Trials will begin in 2025. We hope for positive results from both exams and hope to bring Reyobiq to the market in the next few years, taking into account the FDA’s designation of high-speed trucks and orphans. We also hope to begin enrolling for the 2025 Respect for Pediatric Brain Tumors – PBC Phase 1 Clinical Trial and launch CNSIDE in the third quarter of 2025.
