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BiJ591 solution composition before spray-drying

Prostate-specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase that is highly expressed in nearly all prostate cancers with the highest expression in metastatic castration-resistant prostate cancer (mCRPC). The prevalence of increased surface expression and constitutive internalization of PSMA make it an attractive target for an antibody–drug conjugate (ADC) approach to treating patients with mCRPC. MEDI3726 (previously known as ADCT-401) is an ADC consisting of an engineered version of the anti-PSMA antibody J591 site specifically conjugated to the pyrrolobenzodiazepine (PBD) dimer tesirine. MEDI3726 specifically binds the extracellular domain of PSMA and, once internalized, releases the PBD dimer to crosslink DNA and trigger cell death. In vitro, MEDI3726 demonstrated potent and specific cytotoxicity in a panel of PSMA-positive prostate cancer cell lines, consistent with internalization and DNA interstrand crosslinking. In vivo, MEDI3726 showed robust antitumor activity against the LNCaP and the castration-resistant CWR22Rv1 prostate cancer cell line xenografts. MEDI3726 also demonstrated durable antitumor activity in the PSMA-positive human prostate cancer patient–derived xenograft (PDX) LuCaP models. This activity correlated with increased phosphorylated Histone H2AX in tumor xenografts treated with MEDI3726. MEDI3726 is being evaluated in a phase I clinical trial as a treatment for patients with metastatic castrate-resistant prostate cancer (NCT02991911). Mol Cancer Ther; 17(10); 2176–86. ©2018 AACR.

PDF file - 110K, Supplemental Tables. (S1) Clinical characteristics and CTC data for metastatic prostate cancer patients treated with hormonal therapy. (S2) Time course data for metastatic prostate cancer patients treated with hormonal therapy and analyzed for AR signaling in CTCs.

Small therapeutic proteins represent a promising novel approach to treat cancer. Nevertheless, their clinical application is often adversely impacted by their short plasma half-life. Controlled long-term delivery of small biologicals has become a challenge because of their hydrophilic properties and in some cases their limited stability. Here, an in situ forming depot-injectable polymeric system was used to deliver BiJ591, a bispecific T-cell engager (BiTE) targeting both prostate-specific membrane antigen (PSMA) and the CD3 T-cell receptor in prostate cancer. BiJ591 induced T-cell activation, prostate cancer–directed cell lysis, and tumor growth inhibition. The use of diblock (DB) and triblock (TB) biodegradable polyethylene glycol–poly(lactic acid; PEG-PLA) copolymers solubilized in tripropionin, a small-chain triglyceride, allowed maintenance of BiJ591 stability and functionality in the formed depot and controlled its release. In mice, after a single subcutaneous injection, one of the polymeric candidates, TB1/DB4, provided the most sustained release of BiJ591 for up to 21 days. Moreover, the use of BiJ591-TB1/DB4 formulation in prostate cancer xenograft models showed significant therapeutic activity in both low and high PSMA–expressing tumors, whereas daily intravenous administration of BiJ591 was less efficient. Collectively, these data provide new insights into the development of controlled delivery of small therapeutic proteins in cancer. Mol Cancer Ther; 17(9); 1927–40. ©2018 AACR.

Supplementary Figure S1. Retention of MEDI3726 activity in human, cynomolgus monkey plasma or PBS for up to 7 days. Supplementary Figure S2. Kaplan-Meier analysis of the Time-to-Endpoint Survival in the (A) LNCaP, (B) CWR22Rv1, and (C) PC-3 Xenograft Studies. Supplementary Figure S3. In Vivo Activity of Isotype Control in CWR22Rv1 the Xenograft Model. Supplementary Figure S4. Cytotoxicity of the Warheads and Their Associated ADCs. Supplementary Figure S5. gamma-H2AX IHC Results. Supplementary Figure S6. Body weight measurements from a representative cell line xenograft and a LuCaP PDX in vivo activity studies. Supplementary Figure S7. Hematology Parameters (Males) following MEDI3726 Administration at 0 (control) & 0.6 mg/kg.

Table S1. P values of comparing time to endpoint survival among all treatment groups in the LNCaP xenograft study Table S2. Summary of PSMA IHC in xenograft tumors Table S3. P values of comparing time to endpoint survival among all treatment groups in the CWR22Rv1 xenograft study Table S4. P values of comparing time to endpoint survival among all treatment groups in PC-3 xenograft study

Supplementary Methods

PDF file - 49K, Supplemental Methods for (a) single molecule sequencing and AR transcriptional signature, (b) HB CTC-chip fabrication, (c) HB CTC-chip blood processing, and (d) automated fluorescence microscopy.

PSMA and CD3 expression of targeted cells

Purpose: Standard imaging for assessing osseous metastases in advanced prostate cancer remains focused on altered bone metabolism and is inadequate for diagnostic, prognostic, or predictive purposes. We performed a first-in-human phase I/II study of 89Zr-DFO-huJ591 (89Zr-J591) PET/CT immunoscintigraphy to assess performance characteristics for detecting metastases compared with conventional imaging modalities (CIM) and pathology.Experimental Design: Fifty patients with progressive metastatic castration-resistant prostate cancers were injected with 5 mCi of 89Zr-J591. Whole-body PET/CT scans were obtained, and images were analyzed for tumor visualization. Comparison was made to contemporaneously obtained bone scintigraphy and cross-sectional imaging on a lesion-by-lesion basis and with biopsies of metastatic sites.Results: Median standardized uptake value for 89Zr-J591–positive bone lesions (n = 491) was 8.9 and for soft-tissue lesions (n = 90), it was 4.8 (P < 0.00003). 89Zr-J591 detected 491 osseous sites compared with 339 by MDP and 90 soft-tissue lesions compared with 124 by computed tomography (CT). Compared with all CIMs combined, 89Zr-J591 detected an additional 99 osseous sites. Forty-six lesions (21 bone and 25 soft tissue) were biopsied in 34 patients; 18 of 19 89Zr-J591–positive osseous sites and 14 of 16 89Zr-J591–positive soft tissue sites were positive for prostate cancer. The overall accuracy of 89Zr-J591 was 95.2% (20 of 21) for osseous lesions and 60% (15 of 25) for soft-tissue lesions.Conclusions: 89Zr-J591 imaging demonstrated superior targeting of bone lesions relative to CIMs. Targeting soft-tissue lesions was less optimal, although 89Zr-J591 had similar accuracy as individual CIMs. This study will provide benchmark data for comparing performance of proposed prostate-specific membrane antigen (PSMA) targeting agents for prostate cancer. Clin Cancer Res; 21(23); 5277–85. ©2015 AACR.

Supplementary Table S1. Patient demographics

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Supplementary Figures S1-4. Figure S1. 89Zr-J591 versus bone scan comparison of lesion positivity. Figure S2. Patient with metastatic prostate cancer (PSA of 10.1) with 89Zr-J591+ lesions that were not seen on MDP. Figure S3. Patient with metastatic prostate cancer (PSA of 0.62). Figure S4. Uniform prior distribution.

PDF file - 117K, Supplemental Figure 1A: PSA waterfall plots by dose received. Each individual subjects best PSA response on study. The top figure depicts those subjects who received 65 mCi/m2 and the bottom figure depicts those who received 70 mCi/m2 (the phase I maximum tolerated dose). Supplemental Figure 1B: Circulating Tumor Cell Count waterfall plot Each individual subjects % change in CTC count from baseline to 4-6 weeks following therapy with 70 mCi/m2 of 177Lu-J591. Using the 5 CTC/7.5 mL cutoff, 6 began and remained favorable, 3 converted from unfavorable to favorable (7-->3, 18-->0, 34-->0), and 3 had decline in counts, but remained unfavorable (161-->118, 228-->110, 60-->16). Three subjects had 0 CTCs per 7.5 mL blood at baseline and remained with 0 at follow up. Supplemental Figure 1C: Change in measurable disease Each individual subject with measurable disease is depicted with % change in sum of unidimensional measurements (RECIST). Dose of 177Lu-J591 received is indicted by color.

CCR Translation for This Article from Phase II Study of Lutetium-177–Labeled Anti-Prostate-Specific Membrane Antigen Monoclonal Antibody J591 for Metastatic Castration-Resistant Prostate Cancer

Purpose: To assess the efficacy of a single infusion of radiolabeled anti-prostate-specific membrane antigen (PSMA) monoclonal antibody J591 (lutetium-177; 177Lu) by prostate-specific antigen (PSA) decline, measurable disease response, and survival.Experimental Design: In this dual-center phase II study, two cohorts with progressive metastatic castration-resistant prostate cancer received one dose of 177Lu-J591 (15 patients at 65 mCi/m2, 17 at 70 mCi/m2) with radionuclide imaging. Expansion cohort (n = 15) received 70 mCi/m2 to verify response rate and examine biomarkers.Results: Forty-seven patients who progressed after hormonal therapies (55.3% also received prior chemotherapy) received 177Lu-J591. A total of 10.6% experienced ≥50% decline in PSA, 36.2% experienced ≥30% decline, and 59.6% experienced any PSA decline following their single treatment. One of 12 with measurable disease experienced a partial radiographic response (8 with stable disease). Sites of prostate cancer metastases were targeted in 44 of 47 (93.6%) as determined by planar imaging. All experienced reversible hematologic toxicity, with grade 4 thrombocytopenia occurring in 46.8% (29.8% received platelet transfusions) without significant hemorrhage. A total of 25.5% experienced grade 4 neutropenia, with one episode of febrile neutropenia. The phase I maximum tolerated dose (70 mCi/m2) resulted in more 30% PSA declines (46.9% vs. 13.3%, P = 0.048) and longer survival (21.8 vs. 11.9 months, P = 0.03), but also more grade 4 hematologic toxicity and platelet transfusions. No serious nonhematologic toxicity occurred. Those with poor PSMA imaging were less likely to respond.Conclusion: A single dose of 177Lu-J591 was well tolerated with reversible myelosuppression. Accurate tumor targeting and PSA responses were seen with evidence of dose response. Imaging biomarkers seem promising. Clin Cancer Res; 19(18); 5182–91. ©2013 AACR.

Supplementary Appendix

MOV file - 877K, Ligand-induced AR accumulation in control DMSO-treated PC3-mCherry-�-tubulin cells transfected with GFP-AR.

MOV file - 1.03 MB, Ligand-induced AR accumulation in Docetaxel-treated PC3-mCherry-�-tubulin cells transfected with GFP-AR.

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Prostate-specific membrane antigen (PSMA) is a clinically validated target for prostate cancer. A variety of PSMA-based therapies, including radionuclide- and cytotoxic drug-conjugated and cellular immune products, are in development, each with variable advantages and disadvantages. Here we briefly describe the landscape of PSMA-based therapies beyond 177Lu-PSMA-617, which is covered elsewhere. PATIENT SUMMARY: Prostate-specific membrane antigen (PSMA) is a protein expressed on most prostate cancer tumors and on limited other areas in the body. It can be targeted to treat prostate cancer using radioactive particles, drugs, or immune agents.

Peptide-based prostate-specific membrane antigen (PSMA) targeted radionuclide therapy (TRT) agent [177Lu]-PSMA-617 has emerged as leading TRT candidate for treatment of castration-resistant prostate cancer (mCRPC). [177Lu]-PSMA-617 and other small molecule–based PSMA ligands have shown efficacy in reducing the tumor burden in mCRPC patients but irradiation to the salivary gland and kidneys is a concern and dose-limiting factor. Therefore, methods to reduce non-target organ toxicity are needed to safely treat patients and preserve their quality of life. Herein, we report that addition of cold PSMA ligand PSMA-11 can aid in reducing the uptake of [177Lu]-PSMA-617 in the salivary glands and kidneys. Groups of athymic nude mice (n = 4) bearing PC3-PIP (PSMA+) tumor xenografts were administered with [177Lu]-PSMA-617 along with 0, 5, 100, 500, 1000, and 2000 pmoles of PSMA-11 and biodistribution studies were performed at 1 h. Biodistribution studies at 1 h post-administration revealed that [177Lu]-PSMA-617 uptake in PC3-PIP tumors was 21.71 ± 6.13, 18.7 ± 2.03, 26.44 ± 2.94, 16.21 ± 3.5, 13.52 ± 3.68, and 12.03 ± 1.96 %ID/g when 0, 5, 100, 500, 1000, and 2000 pmoles of PSMA-11 were added, respectively. Corresponding uptake values in kidney were 123.14 ± 52.52, 132.31 ± 47.4, 84.29 ± 78.25, 2.12 ± 1.88, 1.16 ± 0.36, and 0.64 ± 0.23 %ID/g, respectively. Corresponding salivary gland uptake values were 0.48 ± 0.11, 0.45 ± 0.15, 0.38 ± 0.3, 0.08 ± 0.03, 0.09 ± 0.07, and 0.05 ± 0.02 % ID/g, respectively. The uptake of [177Lu]-PSMA-617 in the salivary gland and kidney can be substantially reduced without significantly impacting tumor uptake by adding cold PSMA-11.

Background: PSMA-based targeted radionuclide therapy is now a standard of care for mCRPC since approval of 177Lu-PSMA-617. Use of antibodies (e.g., J591) to target PSMA with higher potency radionuclides (e.g., 225Ac) impacts kinetics, biodistribution, clinical efficacy, and toxicities. In our first-in-human ph I dose-escalation study of single dose 225Ac-J591 in patients with mCRPC, no MTD was reached (max dose 93.3 KBq/kg). Following this, we developed ph I/II parallel dose-escalation studies of fractionated (D1, D15) single cycle and multiple (q6w) dose regimens. Here we present safety data from the initial fractionated study in predominantly 177Lu-naive. Methods: Eligible patients had adequate organ function, ECOG performance status 0-2, and progressive mCRPC following potent AR pathway inhibitor (ARPI) and chemo (or unfit/refusing). Prior 177Lu-PSMA was allowed until an amendment developed a separate study for post-177Lu-PSMA. Baseline 68Ga-PSMA PET scans were performed, but not used to determine eligibility. A 3+3 dose-escalation design was used. Phase I primary objective: determination of dose-limiting toxicity (DLT) and recommended phase II dose (RP2D). DLT was defined as within 8 weeks of first dose: neutropenia (Gr 4 or febrile neutropenia), thrombocytopenia (TCP) (Gr 4, or Gr 3 with clinically significant bleeding), any Gr >2 non-hematologic toxicity deemed to be at least possibly related to 225Ac-J591, or any attributable toxicity precluding or delaying the second dose by >2 weeks. Secondary/exploratory objectives: efficacy measures (e.g., PSA decline, radiographic RR, biochemical/radiographic PFS, OS, CTCs, patient reported outcomes), safety (CTCAE v5), and correlatives (plasma and tissue genomics, PSMA imaging). Results: 24 patients were enrolled in phase I. Median age 73.5 (57-91), PSA 25.78 (3.39-2133.41); 53% (n=13) >1 prior ARPI, 58% (n=14) taxane chemo, 8% (n=2) anti-PSMA therapy, 12.5% (n=3) prior 223Ra. CALGB prognostic groups: Good 4 (16%), Intermediate 8 (33%), Poor 12 (50%). No DLTs were observed in Cohort 1 (n=3) or 2 (n=6). In C3, 2/6 subjects experienced DLTs (Gr 3 weakness, Gr 2 TCP with >2 week delay in second fraction). 8 patients were enrolled in an intermediate dose cohort (2.5) with 1 DLT (Gr 4 TCP). Two patients withdrew before the second dose (intercurrent illness; interruption of 225Ac supply). Most common low gr non-hematologic treatment emergent AEs: fatigue (95%), xerostomia (69%), and nausea (57%). Among evaluable patients for PSA change (n=22), 21 (95%) experienced PSA decline with 14 (67%) with decline of 50% and 6 (37%) with decline of 90%. 13/21 patients had CTCs samples collected at baseline and 12 wks; 5 were unfavorable at baseline (≥5/7.5 mL); 10/13 (77%) remained favorable or converted from unfavorable to favorable; 6/12 (50%) had 50% decline in CTC count; and 5/13 (38%) converted from detectable to undetectable. Conclusions: A single fractionated cycle of 225Ac-J591 was delivered with few high grade AEs and with evidence of preliminary efficacy by PSA and CTC changes across all dose levels. Citation Format: Jones T. Nauseef, Michael Sun, Charlene Thomas, Mahelia Bissassar, Escarleth Fernandez, Zachary Davidson, Amie Patel, Angela Tan, Tessa A. Chamberlain, Kara Earle, Rebecca Wunder, Sabrina Guervil, Sandra H. Castellanos, Judith Stangl-Kremser, Peter S. Gregos, Joseph R. Osborne, Karla V. Ballman, Ana M. Molina, Cora N. Sternberg, David M. Nanus, Neil H. Bander, Scott T. Tagawa. Phase I dose-escalation study of fractionated dose 225Ac J591 for metastatic castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT014.

Accurate diagnosis of localized prostate cancer (PCa) is limited by inadequacy of multiparametric (mp) MRI to fully identify and differentiate localized malignant tissue from benign pathologies. Prostate-specific membrane antigen (PSMA) represents an excellent target for molecular imaging. IAB2M, an 85-kD minibody derived from a de-immunized monoclonal antibody directed at the extracellular domain of human PSMA (huJ591), and PSMA-11, a small molecule ligand have been previously tested as probes for visualization of recurrent/metastatic PCa with PET/CT. This pilot, non-randomized trial studied their diagnostic utility in patients (pts) with localized PCa.Pts planned for radical prostatectomy (RP) were enrolled and underwent mpMRI and PET/CT imaging with20 pts with median age of 64.5 (46-79) years and PSA level of 7.5 (1.6-36.56) ng/ml were enrolled. 19 pts underwent RP and were imaged pre-operatively withIn this pilot study, the performance of

Background Prostate cancer is radiosensitive. Prostate-specific membrane antigen (PSMA) is selectively overexpressed on advanced, castration-resistant tumors. Lutetium-177-labeled anti-PSMA monoclonal antibody J591 (177 Lu-J591) targets prostate cancer with efficacy and dose-response/toxicity data when delivered as a single dose. Dose fractionation may allow higher doses to be administered safely. Method Men with metastatic castration-resistant prostate cancer refractory to or refusing standard treatment options with normal neutrophil and platelet counts were enrolled in initial phase 1b dose-escalation cohorts followed by phase 2a cohorts treated at recommended phase 2 doses (RP2Ds) comprising 2 fractionated doses of 177 Lu-J591 2 weeks apart. 177 Lu-J591 imaging was performed after treatment, but no selection for PSMA expression was performed before enrollment. Phase 2 patients had circulating tumor cell (CTC) counts assessed before and after treatment. Results Forty-nine men received fractionated doses of 177 Lu-J591 ranging from 20 to 45 mCi/m2 ×2 two weeks apart. The dose-limiting toxicity in phase 1 was neutropenia. The RP2Ds were 40 mCi/m2 and 45 mCi/m2 ×2. At the highest RP2D (45 mCi/m2 ×2), 35.3% of patients had reversible grade 4 neutropenia, and 58.8% of patients had thrombocytopenia. This dose showed a greater decrease in prostate-specific antigen (PSA) levels and longer survival (87.5% with any PSA decrease, 58.8% with >30% decrease, 29.4% with >50% decrease; median survival, 42.3 months [95% confidence interval, 19.9-64.7]). Fourteen of 17 (82%) patients with detectable CTCs experienced a decrease in CTC count. Overall, 79.6% of patients had positive PSMA imaging; those with less intense PSMA imaging tended to have poorer responses. Conclusion Fractionated administration of 177 Lu-J591 allowed higher cumulative radiation dosing. The frequency and depth of PSA decrease, overall survival, and toxicity (dose-limiting myelosuppression) increased with higher doses.

INTRODUCTION AND OBJECTIVE:177Lu-PSMA is a promising investigational treatment for men with mCRPC. Optimal selection and biomarkers remain to be defined. Here, we report a combined analysis of men ...

Backgrounds Folate Hydrolase‐1 (FOLH1; PSMA) is a type II transmembrane protein, luminally expressed by solid tumour neo‐vasculature. Monoclonal antibody (mAb), J591, is a vehicle for mAb‐based brachytherapy in FOLH1+ cancers. Brachytherapy is a form of radiotherapy that involves placing a radioactive material a short distance from the target tissue (e.g., on the skin or internally); brachytherapy is commonly accomplished with the use of catheters, needles, metal seeds and antibody or small peptide conjugates. Herein, FOLH1 expression in primary (p) and metastatic (m) Merkel cell carcinoma (MCC) is characterized to determine its targeting potential for J591‐brachytherapy. Materials & Methods Paraffin sections from pMCC and mMCC were evaluated by immunohistochemistry for FOLH1. Monte Carlo simulation was performed using the physical properties of conjugated radioisotope lutetium‐177. Kaplan–Meier survival curves were calculated based on patient outcome data and FOLH1 expression. Results Eighty‐one MCC tumours were evaluated. 67% (54/81) of all cases, 77% (24/31) pMCC and 60% (30/50) mMCC tumours were FOLH1+. Monte Carlo simulation showed highly localized ionizing tracks of electrons emitted from the targeted neo‐vessel. 42% (34/81) of patients with FOLH1+/− MCC had available survival data for analysis. No significant differences in our limited data set were detected based on FOLH1 status (p = 0.4718; p = 0.6470), staining intensity score (p = 0.6966; p = 0.9841) or by grouping staining intensity scores (− and + vs. ++, +++, +++) (p = 0.8022; p = 0.8496) for MCC‐specific survival or recurrence free survival, respectively. Conclusions We report the first evidence of prevalent FOLH1 expression within MCC‐associated neo‐vessels, in 60‐77% of patients in a large MCC cohort. Given this data, and the need for alternatives to immune therapies it is appropriate to explore the safety and efficacy of FOLH1‐targeted brachytherapy for MCC. What's already known about this topic? We report the first evidence of prevalent folate hydrolase‐1 (FOLH1; also known as prostate‐specific membrane antigen) expression within MCC‐associated neovessels. What does this study add? Herein, FOLH1 expression in Merkel cell carcinoma neovasculature is validated, and the therapeutic mechanism of specific, systemic targeting of disseminated disease with antibody‐based brachytherapy, is defined.

Background Prostate-specific membrane antigen (PSMA)-targeted radionuclide therapy (TRT) has demonstrated efficacy and tolerability with a dose-response effect in phase I/II trials in men with metastatic castration-resistant prostate cancer (mCRPC). The need for positive PSMA imaging before PSMA-TRT to select patients is largely practiced, but its utility is not proven. Given target heterogeneity, developing a biomarker to identify the optimal patient population remains an unmet need. The aim of this study was to assess PSMA uptake by imaging and response to PSMA-TRT. Methods We performed an analysis of men with mCRPC enrolled in sequential prospective phase I/II trials of PSMA-TRT. Each patient had baseline PSMA imaging by planar 111 In and/or 177 Lu SPECT (N = 171) or 68 Ga-PSMA-11 PET/CT (N = 44), but the results were not used to include/exclude treatment. Semiquantitative imaging scores (IS) on a 0-4 scale were assigned based on PSMA uptake in tumors compared to liver uptake. We compared the ≥50% PSA decline response proportions between low (0-1) and high (2-4) PSMA IS using the χ2 -test. We used multivariable logistic regression analysis to understand the relationship between independent and dependent variables, including IS, radionuclide activity (dose) administered, CALGB (Halabi) prognostic risk score, prior taxane use. Results 215 men with progressive mCRPC received PSMA-TRT as follows: 177 Lu-J591 (n = 137), 177 Lu-PSMA-617 (n = 44), 90 Y-J591 (n = 28), 177 Lu-J591 + 177 Lu-PSMA-617 (n = 6). High PSMA expression (IS 2-4) was found in 160 (74.4%) patients and was significantly associated with more frequent ≥ 50% PSA reduction (26.2 vs. 7.3%, p = .006). On multivariate logistic regression analysis, higher IS was associated with a ≥50% decrease in PSA, even after accounting for CALGB (Halabi) prognostic score, the dose administered, and previous taxane use (OR, 4.72; 95% CI, 1.71-16.85; p = .006). Patients with low PSMA expression (N = 55, 24.7%) were less likely to respond. Thirteen of 26 (50%) with no PSMA uptake (IS = 0) had post-PSMA-TRT PSA decline with 2 (7.7%) having ≥ 50% PSA declines. Conclusion Collectively, the data provide evidence in favor of the hypothesis that patients with high PSMA uptake and high administered radionuclide dose correlate with a higher chance of response.

The past five years have seen an increasing acceptance of peptide-based prostate-specific membrane antigen (PSMA)-targeted radionuclide therapy (TRT) agents for treatment of metastatic castration-resistant prostate cancer (mCRPC), with [177Lu]-DKFZ-PSMA-617 ([177Lu]-PSMA-617) emerging as the leading candidate. [177Lu]-PSMA-617 and other PSMA ligands have shown efficacy in reducing the tumor burden in mCRPC patients but irradiation to salivary gland and kidneys is a concern and dose limiting factor. Therefore, methods to reduce non-target organ toxicity are needed to safely treat patients and preserve their quality of life. Here, we report the effects of the addition of the cold PSMA ligand DKFZ-PSMA-11 (PSMA-11) on the uptake of [177Lu]-PSMA-617 in tumor, salivary glands and kidneys. Groups of athymic nude mice (n = 4) bearing PC3-PIP (PSMA+) tumor xenografts were administered with [177Lu]-PSMA-617 along with 0, 5, 100, 500, 1000 and 2000 pmoles of PSMA-11. Biodistribution studies 1 h post-administration revealed that [177Lu]-PSMA-617 uptake in PSMA-expressing PC3-PIP tumors was 21.71±6.13, 18.7±2.03, 26.44±2.94, 16.21±3.5, 13.52±3.68, and 12.03±1.96 %ID/g when 0, 5, 100, 500, 1000 and 2000 pmoles of PSMA-11 were added, respectively. Corresponding kidney uptake values were 123.14±52.52, 132.31±47.4, 84.29±78.25, 2.12±1.88, 1.16±0.36, 0.64±0.23 %ID/g, respectively. Corresponding salivary gland uptake values were 0.48±0.11, 0.45±0.15, 0.38±0.3, 0.08±0.03, 0.09±0.07, 0.05±0.02 % ID/g, respectively. Thus, uptake of PSMA TRT agents in salivary gland and kidney can be substantially reduced without impact on tumor uptake by adding cold PSMA-11. Our data provides proof-of-concept and we propose that similar strategy be pursued in future clinical trials to prevent xerostomia and renal toxicity arising from [177Lu]-PSMA-617.

Introduction The Prostate Cancer Foundation (PCF) convened a PCF prostate-specific membrane antigen (PSMA) Theranostics State of the Science Meeting on 18 November 2019, at Weill Cornell Medicine, New York, NY. Methods The meeting was attended by 22 basic, translational, and clinical researchers from around the globe, with expertise in PSMA biology, development and use of PSMA theranostics agents, and clinical trials. The goal of this meeting was to discuss the current state of knowledge, the most important biological and clinical questions, and critical next steps for the clinical development of PSMA positron emission tomography (PET) imaging agents and PSMA-targeted radionuclide agents for patients with prostate cancer. Results Several major topic areas were discussed including the biology of PSMA, the role of PSMA-targeted PET imaging in prostate cancer, the physics and performance of different PSMA-targeted PET imaging agents, the current state of clinical development of PSMA-targeted radionuclide therapy (RNT) agents, the role of dosimetry in PSMA RNT treatment planning, barriers and challenges in PSMA RNT clinical development, optimization of patient selection for PSMA RNT trials, and promising combination treatment approaches with PSMA RNT. Discussion This article summarizes the presentations from the meeting for the purpose of globally disseminating this knowledge to advance the use of PSMA-targeted theranostic agents for imaging and treatment of patients with prostate cancer.

INTRODUCTION AND OBJECTIVE:PSMA is established for TRT with either monoclonal antibodies (mAb) or small molecule ligands. The molecular weight, pharmacokinetics, and biodistribution of mAb vs ligan...

Background: PSMA is overexpressed by the majority of PC and may be targeted by both antibodies (mAb) and small molecule ligands (SML), each with differing PSMA binding sites, kinetics, and biodistributions. mAbs have long circulating times (exposing organs such a bone marrow) but are too large to target normal tissue luminal PSMA expression in salivary glands, small bowel, and kidney; SMLs rapidly diffuse to all PSMA+ sites and are excreted by the kidneys within hours. Alpha emitters have high potency over a short range whereas beta emitters have lower energy over a significantly longer range. We hypothesized that combining mAb and SML targeting plus combining alpha and beta emitters offered complementary benefits and would be safe and effective. Methods: A series of cell line and xenograft studies were performed to test mAb vs SML vs combo binding, uptake, and efficacy. A phase I/II clinical trial was initiated, enrolling patients with progressive, PSMA+ (by PSMA PET) mCRPC following potent AR pathway inhibition and chemotherapy (or chemo ineligible/refused)[NCT04886986]. The primary endpoint of phase I is assessment of dose-limiting toxicity (DLT) with secondary endpoints of response, progression-free and overall survival, genomic and imaging correlatives, and patient-reported outcomes. Results: Binding studies demonstrated that mAb plus SML binding was additive rather than competitive in LNCaP and CWR22Rv1 cell lines. Uptake of 177Lu-mAb plus -SML in LNCaP, CWR22rv1, and PC3/PSMA xenograft models demonstrated synergism, with 44-65% greater tumor radioactivity in combination than the sum of the individual agents. Intracellular tracking studies indicate that the mAb re-directs SML to lysosomes from recycling endosomes, maintains retention of SML in tumor cells, and, therefore, prolongs intra-tumoral radioactivity exposure. Survival was prolonged in animals receiving 225Ac-mAb plus 177Lu-SML vs either drug alone (or control). Nine men with median age 68 (range 55-87), PSA 140 (2.4-9614) have been enrolled in both of 2 planned dose-escalation cohorts. 89% with bone, 44% lymph node, 22% liver, 22% lung metastases; 88% with detectable CTC count (75% unfavorable). All had at least 1 metastatic lesion with PSMA PET SUVmax > liver SUVmean, with SUVmax of the single hottest lesion ranging from 11.6-69.9. For the primary endpoint, 0 of 3 with DLT in cohort 1, and with follow up ongoing, no DLT has occurred to date in 6 patients in cohort 2. Of evaluable patients, 5 of 6 with PSA decline (8-97% decline). Conclusions: Targeting PSMA with the combination of mAb and SML leads to synergistic radioactivity in preclinical studies. The combination on mAb and SML radiolabeled with alpha and beta emitters appears safe with short-term follow up with phase 2 enrollment planned. Citation Format: Scott T. Tagawa, Edward Fung, Muhammad O. Niaz, Mahelia Bissassar, Sharon Singh, Amie Patel, Angela Tan, Juana Martinez Zuloaga, Sandra Huicochea Castellanos, Jones T. Nauseef, Ana Molina, Cora Sternberg, David M. Nanus, Joseph Osborne, Neil H. Bander. Results of combined targeting of prostate-specific membrane antigen (PSMA) with alpha-radiolabeled antibody 225Ac-J591 and beta-radiolabeled ligand 177Lu-PSMA I&T: preclinical and initial phase 1 clinical data in patients with metastatic castration-resistant prostate cancer (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT143.

Prostate specific membrane antigen (PSMA)-targeted radionuclide therapies (PSMA-TRTs) is one of the most promising treatments for metastatic castration-resistant prostate cancer (mCRPC) upon progression on androgen receptor signaling inhibitors (ARPi). However, recent studies show that only about half of patients respond to PSMA-TRTs. Expression of PSMA on cancer cells via PET-imaging is of some use as a predictive biomarker of response to PSMA-TRTs, but there are patients with strong PSMA imaging who do not respond and some with poor PSMA imaging that do respond. PSMA imaging does not fully capture response predictability. Currently, the lack of predictive biomarkers of response limits optimal selection of the patient population most likely to benefit from to PSMA-TRTs. PSMA-TRTs radionuclides emit α or β radiations, which induce DNA damage in targeted cells, followed by immunogenic cell death (ICD), evidenced by calreticulin (CRT) plasma membrane accumulation. To investigate the role of PSMA expression and CRT membrane localization as a biomarker of response to PSMA-TRT, we isolated circulating tumor cells (CTCs) from patients with mCRPC, enrolled in a phase I dose escalation trial of 225Ac-J591 (NCT03276572). Thirty-two (32) patients were enrolled (median age 69. 5, range 52-89; PSA 149.1, range 4.8-7168); 78% and 68% of patients received ≥ 2 prior ARPi treatments or chemotherapy, respectively. 69% and 44% of patients experienced any or >50% PSA decline, respectively, with a median PFS of 5.1 months and median OS of 11.1 months. CTCs were isolated before treatment (baseline) from 30/32 of enrolled patients, and 12 weeks after treatment initiation (on-treatment) from 21/32 patients. Enriched CTCs via CD45 depletion were subsequently immunostained for cytokeratin (CK, standard epithelial marker), CD45 (standard marker to identify contaminating leukocytes), PSMA, calreticulin (CRT) and DAPI. CTCs were subjected to multiplex confocal microscopy and identified as CK+/CD45-/DAPI+ cells. For each patient, at each time point, the following parameters are scored: i) total number of CTCs, ii) number of PSMA+ CTCs, iii) number of CRT+ CTCs, iv) number of CTCs with plasma membrane CRT decoration. Percent of PSMA+ CTC at baseline and changes in percentage of CRT+ CTCs and CTCs with plasma membrane CRT decoration between baseline and on treatment timepoints are correlated with clinical response and time to progression upon 225Ac-J591 treatment. Our preliminary results indicate higher expression of plasma membranous CRT in on-treatment CTCs in responders (PFS>12 months; n= 39 CTCs from 3 patients) than in non-responders (PFS Citation Format: Giuseppe Galletti, Prerna Vatsa, Joseph R. Osborne, Neil H. Bander, David M. Nanus, Scott T. Tagawa, Paraskevi Giannakakou. CTC-based biomarker analysis and correlation with clinical response to PSMA-TRT in mCRPC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1264.

Small therapeutic proteins represent a promising novel approach to treat cancer. Nevertheless, their clinical application is often adversely impacted by their short plasma half-life. Controlled long-term delivery of small biologicals has become a challenge because of their hydrophilic properties and in some cases their limited stability. Here, an in situ forming depot-injectable polymeric system was used to deliver BiJ591, a bispecific T-cell engager (BiTE) targeting both prostate-specific membrane antigen (PSMA) and the CD3 T-cell receptor in prostate cancer. BiJ591 induced T-cell activation, prostate cancer–directed cell lysis, and tumor growth inhibition. The use of diblock (DB) and triblock (TB) biodegradable polyethylene glycol–poly(lactic acid; PEG-PLA) copolymers solubilized in tripropionin, a small-chain triglyceride, allowed maintenance of BiJ591 stability and functionality in the formed depot and controlled its release. In mice, after a single subcutaneous injection, one of the polymeric candidates, TB1/DB4, provided the most sustained release of BiJ591 for up to 21 days. Moreover, the use of BiJ591-TB1/DB4 formulation in prostate cancer xenograft models showed significant therapeutic activity in both low and high PSMA–expressing tumors, whereas daily intravenous administration of BiJ591 was less efficient. Collectively, these data provide new insights into the development of controlled delivery of small therapeutic proteins in cancer. Mol Cancer Ther; 17(9); 1927–40. ©2018 AACR.

The goal of the study was to examine expression of prostate-specific membrane antigen (PSMA) in neovasculature of gynecologic cancers, as PSMA-targeted therapy has showed a promise in treatment of advanced carcinomas. The study included cervical carcinoma (n=28), vulvar carcinoma (n=20), endometrial carcinoma (n=23), primary ovarian carcinoma (n=21), metastatic ovarian carcinoma (n=25), and normal cervix (n=12) as negative control. All cases were immunostained using anti-CD31 antibody to delineate capillary endothelial cells. In parallel, all cases were immunostained using anti-PSMA antibody. The PSMA staining was assessed in tumor capillaries and in normal tissues and scored as a percentage of CD31 staining. PSMA expression was found in the tumor neovasculature, and no significant expression was identified in vasculature of normal tissues. The extent of PSMA staining in tumor capillaries varied from high expression in ovarian and endometrial cancers, to medium expression in cervical squamous cell carcinomas, and low expression in cervical adenocarcinomas and vulvar cancers. All (100%) cases of primary ovarian carcinoma, ovarian carcinoma metastases, and primary endometrial carcinoma showed PSMA expression in tumor vasculature, which was diffuse in majority of cases. The expression of PSMA in ovarian cancer metastases was similar among different metastatic foci of the same tumor. Fifteen percent of cervical squamous cell carcinoma, 50% of cervical adenocarcinoma, and 75% of vulvar carcinomas showed no capillary expression of PSMA. In conclusion, PSMA is highly and specifically expressed in the neovasculature of ovarian, endometrial, and cervical squamous carcinoma, rendering it a potential therapeutic vascular target.

Docetaxel remains a standard of care for metatsatic castration resistant porstate cancer (mCRPC) and has radiosensitizing properties. The dose limiting toxicity (DLT) of radioimmunotherapy is myelosuppression; dose fractionation ofMen with progressive mCRPC received docetaxel 75 mg/mFifteen men with progressive mCRPC received dose-escalated targeted radionuclide therapy in 4 cohorts up to the highest planned dose (2.96 GBq/mThe combination of

Prostate cancer is the most common malignancy and the second leading cause of cancer-related death in men. Radiotherapy is a curative option that is administered via external beam radiation, brachytherapy, or in combination. Erectile, ejaculatory and orgasm dysfunction(s) is/are known potential and common toxicities associated with prostate radiotherapy. Our multidisciplinary team of physicians and/or scientists have written a three (3) part comprehensive review of the pathogenesis and management radiation-induced sexual dysfunction. Part I reviews pertinent anatomy associated with normal sexual function and then considers the pathogenesis of prostate radiation-induced sexual toxicities. Next, our team considers the associated radiobiological (including the effects of time, dose and fractionation) and physical (treatment planning and defining a novel Organ at Risk (OAR)) components that should be minded in the context of safe radiation treatment planning. The authors identify an OAR (i.e., the prostatic plexus) and provide suggestions on how to minimize injury to said OAR during the radiation treatment planning process.

Prostate cancer is the most common malignancy in men and the second leading cause of cancer-related death in men. Radiotherapy is a curative option that is administered via external beam radiation, brachytherapy, or in combination. Sexual dysfunction is a common toxicity following radiotherapy, similar to men undergoing radical prostatectomy, but the etiology is different. The pathophysiology of radiation-induced sexual dysfunction is multi-factorial, and the toxicity is a major cause of impaired quality of life among long-term prostate cancer survivors. Management of a patient's sexual function during and after radiotherapy requires multidisciplinary coordination of care between radiation oncology, urology, psychiatry, pharmacy, and dermatology. This review provides a framework for clinicians to better understand prostatic radiotherapy-induced sexual dysfunction diagnosis, evaluation, and a patient-centered approach to toxicity preventive strategies and management.

LESSONS LEARNED: Hyperfractionation of lutetium‐177 ((177)Lu)‐J591 for patients with metastatic castration‐resistant prostate cancer did not appear to have any additional advantage over the single dose (177)Lu‐J591 or fractionated two‐dose (177)Lu‐J591 therapy. Definite conclusions were challenging because of the small sample size of this study, and so further studies are needed to evaluate the viability of the hypothesis. On the basis of available data, a registration study of (177)Lu‐J591 (also known as TLX591) is planned and will use the two‐dose fractionation schedule (Telix Pharma Q3 2019 update https://telixpharma.com/news-media/). BACKGROUND: Phase I and II single‐dose studies of lutetium‐177 ((177)Lu)‐J591, a radio‐labeled antibody binding prostate‐specific membrane antigen (PSMA), demonstrated safety and efficacy with dose response. Modest dose fractionation of (177)Lu‐J591 (2 doses) has less myelosuppression per similar cumulative dose, allowing higher doses to be administered safely. We hypothesized that additional dose fractionation would allow a higher cumulative dose, potentially with less toxicity and more efficacy. METHODS: Men with progressive metastatic castration‐resistant prostate cancer and adequate organ function were enrolled. (177)Lu‐J591 was administered at 25 mCi/m(2) every 2 weeks until the emergence of related grade 2 toxicity. (177)Lu‐J591 imaging was performed and circulating tumor cell (CTC) counts were measured before and after treatment along with standard monitoring. RESULTS: Six subjects in a single cohort, with a median age of 68.6 years, were enrolled. Patients received three to six doses (cumulative 75−150 mCi/m(2)). Two (33%) patients had >30% prostate‐specific antigen (PSA) decline and three (50%) had CTC count decline. Two (33%) experienced grade (Gr) 4 neutropenia (without fever), three (50%) had Gr 4 thrombocytopenia (without hemorrhage), and two (33%) required platelet transfusions. Following hematological improvement, two patients developed worsening cytopenia during prostate cancer progression; bone marrow biopsies revealed infiltrative tumor replacing normal marrow elements without myelodysplasia. Targeting of known disease sites was seen on planar imaging in all. CONCLUSION: Hyperfractionation of (177)Lu‐J591 is feasible but does not seem to have significant advantages over the two‐dose fractionation regimen.