Kairos Pharma reports 17.7-month median PFS with ENV-105 plus apalutamide versus 2 months with apalutamide alone in a Phase 2 mCRPC trial.
Written By: Charvi Kalal (PharmD)
Reviewed By: Pharmacally Editorial Team
Kairos Pharma, a clinical-stage biopharmaceutical company focused on cancer drug resistance, announced on October 6, 2026, positive interim efficacy data from its ongoing Phase 2 trial of ENV-105 (carotuximab) combined with apalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC).
According to the company, the interim analysis showed a statistically significant difference in progression-free survival (PFS) between patients receiving ENV-105 plus apalutamide and those receiving apalutamide alone. Following the findings, Kairos amended the trial protocol to evaluate ENV-105 earlier in the course of disease progression.
What the Interim Analysis Showed
The company reported a median PFS of 17.7 months with ENV-105 plus apalutamide, compared with 2 months with apalutamide alone (P=0.0008).
PFS measures the time from treatment until disease progression or death from any cause. The reported difference indicates longer progression-free time with the combination in the interim analysis.
The October 2026 update does not disclose the number of patients in each treatment group, hazard ratio, confidence intervals or detailed safety findings. These data will be important for assessing the magnitude, precision and durability of the reported treatment effect.
Earlier ENV-105 Findings
The results follow an earlier interim analysis announced by Kairos in September 2025 involving the first 10 patients enrolled in the trial’s safety lead-in. That analysis reported median PFS of more than 13 months among patients receiving ENV-105 plus apalutamide.
The latest update provides the company’s interim comparison between the combination and apalutamide-alone groups.
About ENV-105
ENV-105, also known as carotuximab, is an investigational antibody targeting CD105 (endoglin). Kairos describes CD105 as a target associated with mechanisms of cancer treatment resistance and relapse.
ENV-105 is being developed as a potential approach to addressing resistance to standard cancer therapies and has not been approved for any indication. Apalutamide, an androgen receptor inhibitor, serves as the treatment backbone in the original Phase 2 study.
Phase 2 Trial Design
The randomized Phase 2 study (NCT05534646), is evaluating ENV-105 in combination with apalutamide in men with metastatic prostate cancer that has become resistant to standard hormone therapy.
Patients have been enrolled at Cedars-Sinai Medical Center, City of Hope and Huntsman Cancer Institute at the University of Utah. Earlier company communications described planned enrollment of up to 100 patients.
The original study compared apalutamide alone with ENV-105 plus apalutamide to assess whether adding ENV-105 could improve outcomes in advanced prostate cancer.
Protocol Amended for Earlier Treatment
Following the interim efficacy signal, Kairos modified the protocol to evaluate ENV-105 earlier in disease progression. The amendment also changes the treatment backbone for the newly defined cohort.
Under the original protocol, patients received either apalutamide alone or ENV-105 plus apalutamide. Under the amended protocol, patients who develop a PSA rise following upfront treatment with an androgen-signaling inhibitor will instead be randomized to enzalutamide alone or enzalutamide plus ENV-105.
The amendment therefore involves both an earlier treatment setting and a change in the androgen-receptor inhibitor backbone from apalutamide to enzalutamide. Kairos said the change is intended to broaden eligibility and facilitate enrollment while evaluating ENV-105 earlier in disease progression.
The company is targeting completion of the Phase 2 trial in or before the fourth quarter of 2027.
Development Strategy and Clinical Context
Kairos Pharma is based in Los Angeles, California, and focuses on developing therapies intended to address cancer drug resistance and immune suppression. ENV-105 is its lead clinical candidate and is also being evaluated in a Phase 1 lung cancer study.
In July 2026, Kairos announced a strategic collaboration with Bayer to evaluate ENV-105 in combination with Xofigo (radium Ra 223 dichloride) in patients with mCRPC involving bone.
The reported 17.7-month median PFS represents an interim company-reported efficacy signal and should be interpreted cautiously until more mature clinical data become available. The absence of treatment-group sizes, hazard ratios, confidence intervals and detailed safety findings limits assessment of the result.
The 2-month median PFS reported for the apalutamide-alone group is shorter than the 3.7-month imaging-based PFS reported for the androgen-signaling inhibitor group in the CARD trial. However, the CARD study involved a different patient population, including patients with mCRPC previously treated with docetaxel and an androgen-signaling inhibitor. The two results therefore should not be considered a direct head-to-head comparison.
ENV-105 remains investigational and has not been approved by the U.S. Food and Drug Administration or other regulatory authorities for prostate cancer.
Next Steps
The amended protocol will allow Kairos to continue evaluating ENV-105 in an earlier treatment setting while using an enzalutamide-based treatment backbone for the newly defined cohort. Further data will be needed to determine whether the interim PFS signal is sustained and translates into a clinically meaningful benefit.
For now, the October 2026 findings provide an interim company-reported efficacy signal for ENV-105 in combination with androgen-receptor pathway inhibition in mCRPC, while the ongoing Phase 2 study continues to evaluate the candidate’s potential in a broader treatment setting.
Reference
Kairos Pharma Reports Positive, Statistically Significant Interim Efficacy Data from Phase 2 Trial of ENV-105 in Metastatic Prostate Cancer, Business Wire (Kairos Pharma, Ltd.), 6 October 2026
Study of AR Suppression with Carotuximab in Metastatic, Castration-Resistant Prostate Canc, ClinicalTrials.gov ID NCT05534646
About the Writer
Charvi Kalal (LinkedIn) is a Pharm.D intern and aspiring medical writer with hands-on experience in medical writing, clinical research, pharmacovigilance, and clinical pharmacy. She has experience in medical content writing through CliMed, along with exposure to ADR monitoring, prescription analysis, patient counselling, literature review, and research documentation. Her research focuses on ADR monitoring and reporting in breast cancer patients receiving targeted therapy. With certifications in GCP, biomedical research, scientific writing, and clinical research, she is passionate about transforming scientific evidence into accurate, engaging, and accessible healthcare content.