Prospects for the use of ipilimumab in treating advanced prostate cancer

Antibody-mediated neutralization of soluble MIC significantly enhances CTLA4 blockade therapy

Antibody therapy targeting cytotoxic T lymphocyte-associated antigen 4 (CTLA4) elicited survival benefits in cancer patients; however, the overall response rate is limited. In addition, anti-CTLA4 antibody therapy induces a high rate of immune-related adverse events. The underlying factors that may influence anti-CTLA4 antibody therapy are not well defined. We report the impact of a cancer-derived immune modulator, the human-soluble natural killer group 2D (NKG2D) ligand sMIC (soluble major histocompatibility complex I chain-related molecule), on the therapeutic outcome of anti-CTLA4 antibody using an MIC transgenic spontaneous TRAMP (transgenic adenocarcinoma of the mouse prostate)/MIC tumor model. Unexpectedly, animals with elevated serum sMIC (sMIC^hi) responded poorly to anti-CTLA4 antibody therapy, with significantly shortened survival due to increased lung metastasis. These sMIC^hi animals also developed colitis in response to anti-CTLA4 antibody therapy. Coadministration of an sMIC-neutralizing monoclonal antibody with the anti-CTLA4 antibody alleviated treatment-induced colitis in sMIC^hi animals and generated a cooperative antitumor therapeutic effect by synergistically augmenting innate and adoptive antitumor immune responses. Our findings imply that a new combination therapy could improve the clinical response to anti-CTLA4 antibody therapy. Our findings also suggest that prescreening cancer patients for serum sMIC may help in selecting candidates who will elicit a better response to anti-CTLA4 antibody therapy.

Immunotherapy in genitourinary malignancies

PURPOSE OF REVIEW

Active investigation suggests immune checkpoint inhibitor therapy and therapeutic cancer vaccines provide clinical benefit for genitourinary malignancies including prostate cancer, renal cell carcinoma, and bladder cancer. Recent developments in the utility of immune checkpoint inhibitor and vaccine therapy for the management of genitourinary malignancies are highlighted in this review.

RECENT FINDINGS

Dramatic responses to checkpoint inhibitor therapy have been demonstrated in renal cell carcinoma and bladder cancer with recent Food and Drug Administration approvals in both indications. No benefit to checkpoint inhibitor therapy has yet been shown for the management of prostate cancer. Therapeutic cancer vaccines have also shown benefit in the treatment of genitourinary malignancies, specifically in the treatment of prostate cancer. Despite advances in these therapeutic modalities, benefit is limited to a subset of patients.

SUMMARY

Current evidence supports the use of immune checkpoint inhibitor therapy and therapeutic cancer vaccines for the management of genitourinary malignancies. Further development of biomarkers for predicting response and study of combination therapy is required to achieve optimal efficacy with these therapeutic interventions.

Immunobiology and immunotherapy in genitourinary malignancies

Immunotherapy has traditionally been a critical component of the cancer treatment armamentarium in genitourinary (GU) cancers. It has an established role in the management of carefully selected patients with metastatic renal cell carcinoma (RCC) [e.g., high dose interleukin-2 (IL-2)] and non-muscle invasive bladder cancer (NMIBC) [e.g., intravesical Bacillus Calmette-Guérin (BCG)]. In 2010, the sipuleucel-T vaccine was approved by the FDA for the management of metastatic castration-resistant prostate cancer (mCRPC), based on a phase III trial showing overall survival (OS) benefit compared to placebo. The immune checkpoint inhibitor nivolumab (anti-PD-1) recently received FDA approval for the management of patients with advanced RCC patients previously treated with anti-angiogenic therapy, based on OS benefit compared to everolimus. Recently, large clinical trials demonstrated meaningful clinical benefit, including durable responses, as well as a good tolerability/safety profile with the use of immune checkpoint inhibitors in advanced RCC and chemotherapy-resistant advanced urothelial carcinoma (UC), while FDA just approved atezolizumab for platinum-treated advanced UC. Numerous interesting trials in different cancers are ongoing. Several combinations of immune checkpoint blockade with chemotherapeutics, vaccines, targeted tyrosine kinase inhibitors & monoclonal antibodies, epigenetic modifiers, anti-angiogenic agents, tumor microenvironment & myeloid cell targeting therapies, metabolic modification strategies, radiation, and others, are being tested in clinical trials. Comprehensive understanding of the factors underlying antitumor immune responses in physiologically relevant animal models and humans will refine further the clinical benefit of immunotherapy. Discovery and validation of appropriate molecular biomarkers via coordinated translational research efforts, rational clinical trial designs with suitable endpoints and well-defined eligibility criteria, prospective registries/databases, careful evaluation of cost-effectiveness and safety/tolerability, adequate funding and open continuous discussions among all stakeholders will support the revolutionary nature of immunotherapy in GU cancers.