Initial clinical experience with [177Lu]Lu-PNT2002 radioligand therapy in metastatic castration-resistant prostate cancer: dosimetry, safety, and efficacy from the lead-in cohort of the SPLASH trial.

SPLASH (NCT04647526) is a multicenter phase III trial evaluating the efficacy and safety of [177Lu]Lu-PNT2002 radioligand therapy in metastatic castration-resistant prostate cancer (mCRPC). This study leveraged a lead-in phase to assess tissue dosimetry and evaluate preliminary safety and efficacy, prior to expansion into a randomized phase. Here we report those results.

Enrolled participants had mCRPC that progressed on one prior androgen receptor pathway inhibitor (ARPI), were prostate-specific membrane antigen (PSMA) PET-positive as determined by a central reader, were chemotherapy-naïve for mCRPC, and had adequate bone marrow and end-organ reserve. Participants received up to 4 cycles of [177Lu]Lu-PNT2002 at 6.8 GBq (± 10%) intravenously per cycle every 8 weeks. Dosimetry (planar + SPECT/CT [n=7]; planar only [n=20]), safety, prostate-specific antigen (PSA) response, objective response rate (ORR), and radiographic progression-free survival (rPFS) per blinded independent central review were assessed.

Of 34 individuals screened, 32 underwent PSMA-PET/CT; 27 met all eligibility criteria. Median (range) age was 72 (57-86) years; all participants were enrolled in North America; 40.7% initiated prior ARPI treatment without distant metastases (M0) and 25.9% while hormone sensitive. Nineteen of 27 (70.4%) participants completed all 4 planned cycles. Organs receiving the largest mean (median, range) specific absorbed doses were lacrimal glands at 1.2 (0.9, 0.4-6.7) Gy/GBq (planar only [n=27]), followed by kidneys at 0.73 (0.63, 0.22-1.8) Gy/GBq (planar + SPECT/CT [n=7]; planar only [n=20]). Mean (median, range) tumor specific absorbed dose was 4.3 (2.1, 0.3-33.4) Gy/GBq (approximately 29 Gy/cycle) based on planar + SPECT/CT of 21 lesions in seven participants. [177Lu]Lu-PNT2002 was associated with no treatment-related deaths, few treatment-related grade ≥3 treatment-emergent adverse events (TEAEs), and no discontinuations for unacceptable toxicity. Treatment-related TEAEs occurring in ≥10% of participants included dry mouth (22.2%; all grade 1), fatigue (18.5%; grades 1-2), nausea (18.5%; grades 1-2), and anemia (14.8%; grades 1-3). Median (95% CI) rPFS was 11.5 (9.2-19.1) months, a PSA decline of ≥50% occurred in 42.3% (11/26) of participants, and confirmed ORR for evaluable disease was 50% (5/10).

[177Lu]Lu-PNT2002, administered at 6.8 GBq/cycle for 4 cycles, demonstrated a favorable dosimetry and safety profile, as well as promising preliminary efficacy.

https://clinicaltrials.gov/, identifier NCT04647526.

Frontiers in oncology. 2025 Jan 07*** epublish ***

Aaron R Hansen, Stephan Probst, Jean-Mathieu Beauregard, Benjamin L Viglianti, Jeff M Michalski, Scott T Tagawa, Oliver Sartor, Ronald F Tutrone, Orhan K Oz, Kevin D Courtney, Ebrahim S Delpassand, Luke T Nordquist, Medhat M Osman, Kim N Chi, Richard Sparks, Noble George, Sara M Hawley, Wenting Wu, Jessica D Jensen, Neil E Fleshner

Department of Medical Oncology, Princess Margaret Cancer Centre, Toronto, ON, Canada., Department of Nuclear Medicine, Jewish General Hospital, Montreal, QC, Canada., Department of Medical Imaging, Center Hospitalier Universitaire (CHU) de Québec - Université Laval, Quebec City, QC, Canada., Department of Radiology, Nuclear Medicine Division, University of Michigan, Ann Arbor, MI, United States., Department of Radiation Oncology, Washington University School of Medicine, Saint Louis, MO, United States., Department of Medicine, Weill Cornell Medical Center, New York, NY, United States., Department of Oncology, Mayo Clinic Rochester, Rochester, MN, United States., Chesapeake Urology Associates (CUA) P.A., Towson, MD, United States., Department of Radiology, University of Texas (UT) Southwestern, Dallas, TX, United States., Department of Internal Medicine, University of Texas (UT) Southwestern, Dallas, TX, United States., Excel Diagnostics and Nuclear Oncology Center, Houston, TX, United States., Urology Cancer Center, PC, Omaha, NE, United States., Department of Radiology, Division of Nuclear Medicine, Saint Louis University Hospital and St. Louis VA Medical Center, St. Louis, MO, United States., Department of Medicine, University of British Columbia, Vancouver, BC, Canada., CDE Dosimetry Services, Knoxville, TN, United States., Department of Clinical Development, POINT Biopharma, a wholly owned subsidiary of Eli Lilly and Company, Indianapolis, IN, United States.