Modulation of Premetastatic Niche by the Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitor Pazopanib in Localized High-Risk Prostate Cancer Followed by Radical Prostatectomy: A Phase II Randomized Trial.

LESSONS LEARNED: Pazopanib was not effective in altering the premetastatic niche in the neoadjuvant setting.Pazopanib was safe and well tolerated without any new safety signals. BACKGROUND: Vascular endothelial growth factor receptor 1 (VEGFR1) expressing myeloid-derived suppressor cells (VEGFR1+ MDSCs) potentially foster metastases by establishing a premetastatic niche. In a preclinical study, VEGFR1+ clustering in lymph nodes (LNs) independently predicted time to biochemical recurrence (TTBR) in localized prostate cancer [1]. The hypothesis was that neoadjuvant pazopanib therapy will decrease VEGFR1+ clusters in pelvic lymph nodes and improve outcomes. METHODS: This is a phase II trial (NCT01832259) of neoadjuvant pazopanib 800 mg versus placebo daily for 4 weeks in high-risk localized prostate cancer. The primary endpoint was a decrease in VEGFR1+ MDSC clustering assessed by immunohistochemistry (IHC) analysis. Secondary endpoints were safety, feasibility, and TTBR. RESULTS: Thirty patients were randomized to pazopanib versus placebo, with 15 patients randomized to each arm. Demographic and disease characteristics were similar in both arms. There was no difference in the VEGFR1+ clustering between the treatment arms (p = .345). Neoadjuvant therapy with pazopanib was well tolerated, and surgical complications were similar in both arms. CONCLUSION: Neoadjuvant pazopanib therapy did not alter the premetastatic niche; however, treatment targeting vascular endothelial growth factor (VEGF) in the preoperative period was safe and feasible, which may open up the avenue to investigate novel combinatorial regimens, including a VEGF inhibitor in combination with immune checkpoint inhibitor in this setting.

Prospective Evaluation of Bone Metabolic Markers as Surrogate Markers of Response to Radium-223 Therapy in Metastatic Castration-resistant Prostate Cancer.

PURPOSE: Radium-223 is approved for metastatic castration-resistant prostate cancer (mCRPC) based on improved overall survival, and delay in skeletal related events. However, it is not associated with PSA or radiographic response, which poses a challenge in real-time assessment of its efficacy. Surrogate markers of treatment outcomes may facilitate tailoring treatment duration with radium-223, by limiting the duration of therapy with radium-223 in these patients. Here, we sought to investigate the utility of bone metabolic markers (BMMs) as surrogate markers of response to radium-223 in mCRPC. PATIENTS AND METHODS: A prospective phase II trial of radium-223 plus enzalutamide (RE) versus enzalutamide alone was designed to assess surrogacy of BMMs with respect to response to radium-223. Enzalutamide was used as a comparator in lieu of placebo due to the progressive disease. Co-primary endpoints were relative change in serum BMM N-telopeptide (NTP) levels from baseline to 6 months between the two arms and safety and feasibility of the combination. RESULTS: Thirty-nine men were randomized to RE (n = 27) or enzalutamide (n = 12). Combination was safe and feasible. Primary endpoint was met. A statistically significant relative change to NTP ratios between arms (0.64, 95% confidence interval, 0.51-0.81; P = 0.00048) favored RE versus enzalutamide. Overall, BMMs decreased with the RE therapy compared with enzalutamide. Improved PSA response rate in RE versus enzalutamide (P = 0.024), correlated with decline in BMMs. CONCLUSIONS: BMMs declined significantly with combination therapy, and were associated with improved outcomes. Upon external validation, BMMs may emerge as surrogate markers to monitor treatment with radium-223 in real-time.

Randomized phase II trial of sipuleucel-T immunotherapy preceded by sensitizing radiation therapy and sipuleucel-T alone in patients with metastatic castrate resistant prostate cancer.

BACKGROUND: Sipuleucel-T is an autologous cellular immunotherapy indicated for patients with asymptomatic or minimally symptomatic metastatic castration resistant prostate cancer (mCRPC). Since radiation therapy (RT) can suppress bone marrow function and immune responses, previous studies evaluating sipuleucel-T excluded patients who received RT less than or equal to 28 days prior to sipuleucel-T therapy. Recent evidence suggests that RT may act synergistically with immunotherapy to enhance and broaden antitumor immune response. METHODS: Patients who met standard criteria for sipuleucel-T were randomized to receive sipuleucel-T alone (Arm A) or sipuleucel-T initiated 1 week after completing sensitizing RT to single metastatic site (Arm B). RT was delivered at 300cGy/day to 3000 cGy total. The primary endpoint was the ability to safely combine sipuleucel-T preceded by RT and generate sipuleucel-T with adequate product immune activation parameters. Secondary endpoints included the measurement of systemic immune responses to prostatic acid phosphatase (PAP), a target for sipuleucel-T immune therapy and PA20204 (recombinant fusion protein utilized in the generation of sipuleucel-T). RESULTS: 51 pts were enrolled, 2 did not receive any sipuleucel-T because of vascular access problems and were excluded. 24 were treated on Arm A, 25 on Arm B. 47/49 patients received all 3 sipuleucel-T infusions. Median age was 66 yrs (range 45-90). Sipuleucel-T product parameters including: total nucleated cell (TNC) count, antigen presenting cell (APC) count were similar in both groups. Cumulative APC upregulation was higher in Arm A. 1 patient in Arm A demonstrated PSA response. Median progression free survival (PFS) was 2.46 months on Arm A and 3.65 months on Arm B (p = 0.06). Both arms showed similar increases in humoral responses to PA2024 and PAP. IFN-ƴ ELISPOT T-cell activation responses to PA20204 were observed in both arms, but were more robust in the Arm A (p = 0.028). Both arms were well-tolerated, with fatigue as the most common grade 2 adverse event (1 patient in Arm A and 3 patients in Arm B). CONCLUSIONS: Sensitizing RT completed 1 week before generation of sipuleucel-T did not affect the majority of product parameters and the ability to deliver sipuleucel-T therapy. RT did not enhance the humoral and cellular responses associated with sipuleucel-T therapy.