Kairos Pharma and Bayer Partner to Advance Combination Therapy for Metastatic Prostate Cancer
Kairos Pharma, Ltd., a clinical-stage biopharmaceutical company focused on developing therapies that overcome cancer drug resistance, has announced a strategic research collaboration with Bayer to evaluate its lead investigational antibody, ENV-105 (carotuximab), in combination with XOFIGO® (radium-223 dichloride) for the treatment of metastatic castration-resistant prostate cancer (mCRPC) with bone involvement. The collaboration reflects a shared commitment to exploring innovative therapeutic strategies that may improve outcomes for patients whose disease continues to progress despite currently available treatment options.
The partnership brings together Kairos Pharma’s expertise in targeting mechanisms of therapeutic resistance with Bayer’s established radiopharmaceutical therapy, creating an opportunity to investigate whether combining these two approaches can provide deeper, more durable responses for patients with advanced prostate cancer.
Addressing One of the Biggest Challenges in Advanced Prostate Cancer
Metastatic castration-resistant prostate cancer represents one of the most difficult stages of prostate cancer to treat. Although advances in hormonal therapy, chemotherapy, targeted agents, immunotherapy, and radiopharmaceuticals have significantly improved patient care over the past decade, many patients eventually develop resistance to treatment. As tumors adapt to therapeutic pressure, cancer cells activate alternative biological pathways that allow continued growth and spread.
Bone metastases are particularly common in advanced prostate cancer and are associated with severe complications, including chronic pain, fractures, spinal cord compression, reduced mobility, and diminished quality of life. Managing both disease progression and skeletal complications remains a major clinical priority.
The collaboration between Kairos Pharma and Bayer is designed to investigate whether targeting resistance mechanisms while simultaneously delivering targeted radiation to bone metastases can improve disease control compared with existing therapeutic approaches.
ENV-105: A Novel First-in-Class Approach
ENV-105, also known as carotuximab, is Kairos Pharma’s lead investigational antibody therapy. The treatment targets CD105, a protein involved in tumor angiogenesis and cellular signaling pathways that contribute to cancer progression and treatment resistance.
Unlike conventional therapies that primarily focus on eliminating cancer cells directly, ENV-105 aims to interfere with biological mechanisms that enable tumors to survive therapeutic interventions.
The antibody inhibits CD105/BMP signaling, a pathway increasingly recognized as playing a central role in the development of resistance to multiple classes of cancer therapies. By disrupting these signaling mechanisms, researchers believe ENV-105 may restore tumor sensitivity to existing treatments and extend their clinical effectiveness.
Because this mechanism differs from many currently available therapies, ENV-105 has attracted considerable interest as a potential first-in-class therapeutic candidate.
Clinical Development Progress
Kairos Pharma has already advanced ENV-105 into multiple clinical programs across different cancer indications.
The company is currently evaluating the antibody in:
- A Phase 1 clinical trial in patients with EGFR-driven non-small cell lung cancer.
- A Phase 2 clinical trial in patients with metastatic castration-resistant prostate cancer.
The prostate cancer program has already generated encouraging interim clinical findings.
Last year, Kairos Pharma reported positive interim efficacy data showing that patients receiving ENV-105 achieved a median progression-free survival exceeding 13 months, representing a meaningful improvement compared with historical expectations under standard treatment approaches.
These results were presented during the 2025 European Society for Medical Oncology (ESMO) Congress in Berlin, highlighting growing scientific interest in the therapy’s potential role in addressing drug resistance.
While additional studies are necessary to confirm these findings, the early data have supported continued clinical development and the initiation of new combination studies.
XOFIGO: An Established Radiopharmaceutical Therapy
Bayer’s XOFIGO (radium-223 dichloride) is a well-established targeted radiopharmaceutical approved by the U.S. Food and Drug Administration for patients with metastatic castration-resistant prostate cancer involving symptomatic bone metastases.
Unlike external beam radiation, XOFIGO delivers highly localized alpha-particle radiation directly to areas of increased bone turnover associated with metastatic lesions.
This targeted approach enables the therapy to selectively damage cancer cells in bone while minimizing exposure to surrounding healthy tissues.
Since its introduction, XOFIGO has become an important treatment option for patients with advanced prostate cancer, particularly those experiencing symptomatic skeletal disease.
Bayer continues to expand the clinical utility of XOFIGO through multiple combination studies aimed at improving efficacy and extending patient benefit.
Building on Recent Phase III Momentum
The collaboration also builds upon encouraging evidence generated from Bayer’s ongoing development program.
Among the most notable advances is the Phase III PEACE-3 trial, which evaluated XOFIGO in combination with enzalutamide.
According to reported study findings, the combination demonstrated a 24% reduction in mortality risk, achieving a hazard ratio of 0.76 with statistical significance.
These encouraging results reinforce growing interest in combining XOFIGO with complementary therapies capable of enhancing treatment response through different biological mechanisms.
Kairos Pharma believes ENV-105 may represent another promising partner for XOFIGO due to its distinct mechanism targeting therapy resistance.
Scientific Rationale for the Combination
The biological foundation supporting this collaboration centers on CD105.
Previous preclinical research has demonstrated that CD105 expression increases following androgen receptor inhibition as well as exposure to ionizing radiation.
This increased expression activates BMP-SMAD signaling pathways, which promote tumor survival and contribute to resistance against multiple treatment modalities.
By inhibiting CD105, ENV-105 may interrupt these adaptive survival mechanisms.
Researchers believe this could make tumor cells more vulnerable to the cytotoxic effects of XOFIGO’s targeted alpha radiation.
Earlier laboratory studies have already demonstrated that ENV-105 can function as a radiation sensitizer in prostate cancer models, providing additional scientific support for evaluating the combination in clinical settings.
If validated in human studies, the approach could potentially improve both the depth and duration of therapeutic responses.
Leadership Highlights Potential Clinical Impact
Dr. John Yu, Chief Executive Officer of Kairos Pharma, emphasized that overcoming therapeutic resistance remains one of the company’s central goals.
He noted that while therapies such as XOFIGO have significantly improved patient care, many tumors eventually develop resistance, limiting long-term effectiveness.
According to Dr. Yu, ENV-105 has already demonstrated the ability to restore tumor sensitivity to existing therapies while maintaining a favorable safety profile.
He described the collaboration with Bayer as an important milestone that could support the development of longer-lasting and more effective treatment regimens for patients with metastatic prostate cancer.
Expanding Evidence Around CD105
Dr. Neil Bhowmick, Chief Scientific Officer and Principal Investigator at Kairos Pharma, highlighted the growing body of scientific evidence supporting CD105 as a key therapeutic target.
He explained that CD105 has now been implicated as a common mechanism underlying resistance across several different treatment classes.
This growing understanding makes combining ENV-105 with XOFIGO both scientifically compelling and clinically relevant, particularly in light of the recent positive momentum surrounding Bayer’s radiopharmaceutical development program.
According to Dr. Bhowmick, targeting resistance pathways while preserving the benefits of established therapies could represent an important advancement in prostate cancer treatment.
Potential Benefits for Patients
If the combination ultimately proves successful during clinical evaluation, it may offer several potential advantages for patients with advanced metastatic prostate cancer.
Potential benefits under investigation include:
- Improved progression-free survival.
- Longer duration of response to therapy.
- Enhanced sensitivity to radiopharmaceutical treatment.
- Reduced development of treatment resistance.
- Better management of metastatic bone disease.
- Potential improvements in overall survival.
These outcomes remain investigational and will require confirmation through carefully designed clinical trials before any regulatory conclusions can be drawn.
Importance of Combination Therapy in Oncology
The collaboration reflects a broader trend across oncology toward rational combination therapies that attack cancer through multiple complementary mechanisms.
Rather than relying on a single therapeutic approach, researchers increasingly recognize that combining targeted therapies with immunotherapies, radiopharmaceuticals, chemotherapy, or hormone therapy may produce stronger and more durable clinical responses.
Understanding the biological pathways responsible for resistance has become one of the most active areas of cancer research.
As scientists identify molecular drivers such as CD105, new opportunities emerge to combine targeted agents with established therapies in ways that could significantly improve long-term disease control.
The strategic partnership between Kairos Pharma and Bayer represents an important step in advancing innovative treatment strategies for metastatic castration-resistant prostate cancer. By combining ENV-105’s novel CD105/BMP signaling inhibition with the targeted alpha-emitting radiopharmaceutical XOFIGO, the companies aim to explore a scientifically grounded approach to overcoming one of the greatest obstacles in cancer treatment—therapeutic resistance.
As clinical evaluation progresses, investigators will assess whether this combination can deliver meaningful improvements in efficacy while maintaining an acceptable safety profile. Positive results could not only strengthen the role of ENV-105 in prostate cancer but also provide broader insights into targeting resistance mechanisms across multiple oncology indications.
With encouraging early clinical data, expanding scientific evidence, and growing interest in combination therapies, the collaboration underscores the continued commitment of both companies to advancing innovative cancer treatments that have the potential to improve outcomes for patients facing advanced metastatic disease.
About Kairos Pharma Ltd.
Based in Los Angeles, California, Kairos Pharma Ltd. (NYSE American: KAPA) is at the forefront of oncology therapeutics, utilizing structural biology to overcome drug resistance and immune suppression in cancer. Kairos Pharma’s lead candidate, ENV-105, is an antibody that targets CD105—a protein identified as a key driver of resistance and disease relapse in response to standard therapy. ENV-105 aims to reverse drug resistance by targeting CD105 and restore the effectiveness of standard therapies across multiple cancer types. For more information, visit kairospharma.com.