A Retrospective Observational Analysis of Overall Survival with Sipuleucel-T in Medicare Beneficiaries Treated for Advanced Prostate Cancer

Healthcare Costs in Men with Metastatic Castration-Resistant Prostate Cancer: An Analysis of US Medicare Fee-For-Service Claims

INTRODUCTION

To analyze healthcare resource utilization (HRU) and healthcare costs in men with metastatic castration-resistant prostate cancer (mCRPC) in the US Medicare population.

METHODS

A published claims-based algorithm was used to identify men with mCRPC in the fee-for-service Medicare population between January 1, 2014, and December 31, 2019. Unadjusted all-cause HRU (days) and healthcare costs paid by Medicare (medical and pharmacy) per patient per year (PPPY) are described for the periods before mCRPC diagnosis, after diagnosis, and from the start of first-line (1L), second-line (2L), and third-line (3L) therapy with mCRPC life-prolonging treatments to the start of subsequent therapy or end of follow-up/death.

RESULTS

A total of 14,780 men with mCRPC were identified. After mCRPC diagnosis, 11,528 men initiated 1L mCRPC therapy, 6275 initiated 2L, and 2945 initiated 3L. All-cause medical HRU (days PPPY) increased after mCRPC diagnosis and from 1L through 3L treatment, particularly for outpatient care (pre-diagnosis, 10.4; 1L, 16.2; 2L, 18.9; 3L, 22.0) and physician/other visits (pre-diagnosis, 30.1; 1L, 46.5; 2L, 50.2; 3L, 56.9). Similarly, mean all-cause healthcare costs PPPY were $27,468 in the year before mCRPC diagnosis and increased over four fold to $124,379 after mCRPC diagnosis and continued to rise from start of 1L ($148,325) to 2L ($160,118) to 3L ($165,186) therapy.

CONCLUSION

HRU and healthcare costs increased substantially following mCRPC diagnosis, and continued to increase even further through progression from 1L through 3L mCRPC therapy. These findings help to quantify the economic burden of mCRPC and to contextualize the economic value of treatments that delay disease progression.

Prostate-specific antigen response and clinical progression-free survival in Black and White men with chemotherapy-naïve metastatic castration-resistant prostate cancer treated with enzalutamide in a real-world setting

BACKGROUND

In the United States, Black men have a higher incidence of prostate cancer (PC)-related mortality than men of other races. Several real-world studies in advanced PC suggest, however, that Black men respond better to novel hormonal therapies than White men. Data on treatment responses to enzalutamide by race are limited. We assessed real-world prostate-specific antigen (PSA) response and clinical progression-free survival (cPFS) of Black vs. White men with chemotherapy-naïve PC treated with enzalutamide.

METHODS

This retrospective cohort study included patients with PC who initiated enzalutamide treatment from 2014 to 2018 in the IntrinsiQ Specialty Solutions™ database, a collection of electronic medical records from community urology practices. Index date was the date of the first prescription for enzalutamide, used as a proxy for metastatic castration-resistant PC (mCRPC). Patients who had undergone chemotherapy and/or abiraterone therapy were excluded. Kaplan-Meier and Cox models adjusted for baseline characteristics were used to estimate PSA response and cPFS by race.

RESULTS

The study included 214 Black and 1332 White men with chemotherapy-naïve PC presumed to have mCRPC based on the enzalutamide indication during the study period. Black men were younger and had higher baseline median PSA levels than White men. Enzalutamide therapy duration, follow-up time, and number of post-index PSA tests were similar between races. In multivariable analyses, the risk of patients achieving a ≥ 50% PSA decline was similar, whereas a numerically higher trend of ≥90% PSA decline was observed in Black men (HR 1.23; 95% CI 0.93-1.62 [P = 0.14]). In the multivariable analysis, Black men had significantly better cPFS (HR 0.82; 95% CI 0.68-0.98 [P = 0.03]).

CONCLUSIONS

Black and White men with presumed chemotherapy-naïve mCRPC had similar PSA responses when treated with enzalutamide, but Black men had better cPFS than White men. Further research is warranted to validate these findings.

Combination Treatment with Sipuleucel-T and Abiraterone Acetate or Enzalutamide for Metastatic Castration-Resistant Prostate Cancer: STAMP and STRIDE Trials

PURPOSE

We present long-term outcomes from 2 randomized studies [STAMP (with abiraterone, NCT01487863) and STRIDE (with enzalutamide, NCT01981122)] that were performed to study the impact of sequential or concurrent administration of androgen receptor-targeting agents (ARTAs) on sipuleucel-T immune response and overall survival (OS) in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Sipuleucel-T was administered per current prescribing information. Results from STRIDE are presented together with updated STAMP results. Survival status of patients was updated using demographic information to query the National Death Index (NDI). Kaplan-Meier methodology was used to analyze survival.

RESULTS

Updated data reduced patient censoring in each study compared with the original analyses; the 95% confidence intervals (CIs) for OS are now estimable. Updated median OS (95% CI) is 33.3 (24.1-40.7) months for STAMP and 32.5 (26.0-45.1) months for STRIDE. There was no notable impact on median OS [HR, 0.727 (0.458-1.155); P = 0.177, reference = STRIDE]. OS with sequential administration was similar to concurrent administration [NDI update: HR, 0.963 (0.639-1.453); P = 0.845, reference = concurrent arm]. Sipuleucel-T potency, measured as antigen-presenting cell (APC) activation, was higher in subsequent infusions compared with the first infusion. Humoral responses (IgG + IgM antibody titers) to PA2024 and prostatic acid phosphatase were significantly elevated versus baseline. No new safety signals were observed.

CONCLUSIONS

Median OS was consistent regardless of whether the agents were administered sequentially or concurrently, including after NDI update. Results suggest that sipuleucel-T induces an immunologic prime-boost effect after initial sipuleucel-T exposure, even when combined with ARTAs.

Tissue-Targeted Drug Delivery Strategies to Promote Antigen-Specific Immune Tolerance

During autoimmunity or organ transplant rejection, the immune system attacks host or transplanted tissue, causing debilitating inflammation for millions of patients. There is no cure for most of these diseases. Further, available therapies modulate inflammation through nonspecific pathways, reducing symptoms but also compromising patients' ability to mount healthy immune responses. Recent preclinical advances to regulate immune dysfunction with vaccine-like antigen specificity reveal exciting opportunities to address the root cause of autoimmune diseases and transplant rejection. Several of these therapies are currently undergoing clinical trials, underscoring the promise of antigen-specific tolerance. Achieving antigen-specific tolerance requires precision and often combinatorial delivery of antigen, cytokines, small molecule drugs, and other immunomodulators. This can be facilitated by biomaterial technologies, which can be engineered to orient and display immunological cues, protect against degradation, and selectively deliver signals to specific tissues or cell populations. In this review, some key immune cell populations involved in autoimmunity and healthy immune tolerance are described. Opportunities for drug delivery to immunological organs are discussed, where specialized tissue-resident immune cells can be programmed to respond in unique ways toward antigens. Finally, cell- and biomaterial-based therapies to induce antigen-specific immune tolerance that are currently undergoing clinical trials are highlighted.

Real-World Effectiveness of Sipuleucel-T on Overall Survival in Men with Advanced Prostate Cancer Treated with Androgen Receptor-Targeting Agents

Introduction

The treatment landscape for metastatic castration-resistant prostate cancer (mCRPC) continues to evolve. Sipuleucel-T was the first immunotherapy approved by the US Food and Drug Administration (FDA) to treat asymptomatic or minimally symptomatic mCRPC. The androgen receptor-targeting agents (ARTAs) abiraterone acetate and enzalutamide were initially approved to treat mCRPC. Looking at chemotherapy-naïve men with mCRPC, we compared survival outcomes between the sipuleucel-T + ARTA cohort (men who received either sipuleucel-T or an ARTA in the first line, and then the other in the second line within 6 months) and the ARTA monotherapy cohort (men who only received ARTA monotherapy).

Methods

This retrospective cohort analysis used longitudinal, adjudicated claims data from the US Medicare Fee-for-Service 100% research identifiable dataset that includes both urologic and oncologic practice settings. Eligible men started their first mCRPC treatment with either sipuleucel-T or ARTA in either 2014 or 2015 and had continuous Medicare Parts A, B, and D eligibility for the subsequent 3 years. A multivariable Cox proportional hazards regression model was used to analyze overall survival (OS), both overall and by index year, and to control for differences.

Results

The sipuleucel-T + ARTA and ARTA monotherapy cohorts comprised 773 and 4642 men, respectively, with different characteristics at treatment start. The most commonly used ARTAs were enzalutamide in the former and abiraterone in the latter cohort. Median OS was 30.4 and 14.3 months in the sipuleucel-T + ARTA and ARTA monotherapy cohorts, respectively, with the sipuleucel-T + ARTA cohort having a 28.3% lower risk of death than the ARTA monotherapy cohort (hazard ratio 0.717; 95% CI 0.648, 0.793; p < 0.01).

Conclusions

This real-world study of mCRPC treatment indicates that men receiving sipuleucel-T and ARTAs had a longer median OS than patients receiving treatment with an ARTA alone, suggesting that leveraging mechanisms of action can be beneficial in treating patients with mCRPC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-022-02085-6.

The treatment landscape for metastatic castration-resistant prostate cancer (mCRPC) continues to evolve. There are multiple treatments for mCRPC, including sipuleucel-T, the first US Food and Drug Administration (FDA)-approved immunotherapy, and the androgen receptor-targeting agents (ARTAs) abiraterone acetate and enzalutamide. Although sipuleucel-T uses a unique mechanism of action that may be useful in developing a treatment strategy for mCRPC, an optimal treatment algorithm for prostate cancer remains undefined. Therefore, survival was compared in men with mCRPC who received sipuleucel-T and an ARTA in the first 6 months of treatment with those who received only ARTA monotherapy. A retrospective longitudinal study was conducted using the US Medicare Fee-for-Service 100% research identifiable dataset linked to the National Death Index. Eligible men started their first mCRPC treatment with either sipuleucel-T or ARTA in either 2014 or 2015 and had continuous Medicare eligibility for the subsequent 3 years. Men who received treatment with both sipuleucel-T and an ARTA had a longer median survival (30.4 months) than men who received an ARTA without sipuleucel-T (14.3 months). This represents a 28% reduced risk of death with sipuleucel-T. This real-world study of mCRPC treatment indicates that men receiving sipuleucel T and an ARTA survive longer than men who only receive an ARTA, suggesting that changing the mechanism of action can be beneficial in treating patients with mCRPC.

Outcomes in men with metastatic castration-resistant prostate cancer who received sipuleucel-T and no immediate subsequent therapy: experience at Dana Farber and in the PROCEED Registry

BACKGROUND

Sipuleucel-T has demonstrated survival benefit in phase 3 trials but is utilized in few men with metastatic castration-resistant prostate cancer (mCRPC) in part due to low rates of PSA and objective response. Given the requirement to develop immune-mediated antitumor activity as vaccine-based therapy, sipuleucel-T may have delayed clinical activity. We explored this in a cohort of men from PROCEED (NCT01306890), an FDA-requested outcomes registry, and in a separate institutional cohort of mCRPC patients treated with sipuleucel-T at Dana-Farber Cancer Institute (DFCI).

METHODS

Men with mCRPC who received 3 infusions of sipuleucel-T and did not initiate a new mCRPC directed therapy for ≥6 months after completion of sipuleucel-T were included. All patients had rising PSA before starting sipuleucel-T and available post-treatment PSA measurements. Clinical outcomes of interest included: PSA₅₀ response rate, time to subsequent mCRPC directed therapy, and overall survival (OS).

RESULTS

Of 1902 men with mCRPC treated in PROCEED and 255 patients treated consecutively with sipuleucel-T between 4/2010 and 4/2017 at DFCI, 171 and 28 patients were included, respectively. In the PROCEED sample, PSA₅₀ response was observed in 34 (19.9%) of patients at a median of 5.5 months (IQR: 3.9-9.5) since the last sipuleucel-T infusion; median time to subsequent mCRPC directed therapy was 10 months (95% CI: 9-11); and median OS was 49 months (95% CI: 43-NR). In the DFCI cohort, PSA₅₀ response was observed in 4 (14.3%) of patients at a median of 6.3 months (IQR: 4.7-7.0); median time to subsequent mCRPC directed therapy was 9 months (95% CI: 9-11); and median OS was 60 months (95% CI: 51-74).

CONCLUSIONS

In this analysis of mCRPC patients treated with sipuleucel-T who did not immediately initiate subsequent therapy using two datasets, delayed PSA response was observed in a subset of patients indicating delayed clinical activity.

Phase Ib study of patients with metastatic castrate-resistant prostate cancer treated with different sequencing regimens of atezolizumab and sipuleucel-T

Background

Combining an immune checkpoint inhibitor with a tumor vaccine may modulate the immune system to leverage complementary mechanisms of action that lead to sustained T-cell activation and a potent prolonged immunotherapeutic response in metastatic castration resistant prostate cancer (mCRPC).

Methods

Subjects with asymptomatic or minimally symptomatic mCRPC were randomly assigned in a 1:1 ratio to receive either atezolizumab followed by sipuleucel-T (Arm 1) or sipuleucel-T followed by atezolizumab (Arm 2). The primary endpoint was safety, while secondary endpoints included preliminary clinical activity such as objective tumor response and systemic immune responses that could identify key molecular and immunological changes associated with sequential administration of atezolizumab and sipuleucel-T.

Results

A total of 37 subjects were enrolled. The median age was 75.0 years, median prostate specific antigen (PSA) was 21.9 ng/mL, and subjects had a median number of three prior treatments. Most subjects (83.8%) had at least one treatment-related adverse event. There were no grade 4 or 5 toxicities attributed to either study drug. Immune-related adverse events and infusion reactions occurred in 13.5% of subjects, and all of which were grade 1 or 2. Of 23 subjects with Response Evaluation Criteria in Solid Tumors measurable disease, only one subject in Arm 2 had a partial response (PR) and four subjects overall had stable disease (SD) at 6 months reflecting an objective response rate of 4.3% and a disease control rate of 21.7%. T-cell receptor diversity was higher in subjects with a response, including SD. Immune response to three novel putative antigens (SIK3, KDM1A/LSD1, and PIK3R6) appeared to increase with treatment.

Conclusions

Overall, regardless of the order in which they were administered, the combination of atezolizumab with sipuleucel-T appears to be safe and well tolerated with a comparable safety profile to each agent administered as monotherapy. Correlative immune studies may suggest the combination to be beneficial; however, further studies are needed.

Trial registration number

NCT03024216.

Regenerative medicine clinical readiness

Regenerative medicine, poised to transform 21st century healthcare, has aspired to enrich care options by bringing cures to patients in need. Science-driven responsible and regulated translation of innovative technology has enabled the launch of previously unimaginable care pathways adopted prudently for select serious diseases and disabilities. The collective resolve to advance the design, manufacture and validity of affordable regenerative solutions aims to democratize such health benefits for all. The objective of this Review is to outline the framework and prerequisites that underpin clinical readiness of regenerative care. Integrated research and development, specialized workforce education and accessible evidence-based practice implementation are at the core of realizing an equitable regenerative medicine vision.

Vaccine Therapies for Cancer: Then and Now

There are strong biologic and preclinical rationales for the development of therapeutic cancer vaccines; however, the clinical translation of this treatment strategy has been challenging. It is now understood that many previous clinical trials of cancer vaccines used target antigens or vaccine designs that inherently lacked sufficient immunogenicity to induce clinical responses. Despite the historical track record, breakthrough advances in cancer immunobiology and vaccine technologies have supported continued interest in therapeutic cancer vaccinations, with the hope that next-generation vaccine strategies will enable patients with cancer to develop long-lasting anti-tumor immunity. There has been substantial progress identifying antigens and vaccine vectors that lead to strong and broad T cell responses, tailoring vaccine designs to achieve optimal antigen presentation, and finding combination partners employing complementary mechanisms of action (e.g., checkpoint inhibitors) to overcome the diverse methods cancer cells use to evade and suppress the immune system. Results from randomized, phase 3 studies testing therapeutic cancer vaccines based on these advances are eagerly awaited. Here, we summarize the successes and failures in the clinical development of cancer vaccines, address how this historical experience and advances in science and technology have shaped efforts to improve vaccines, and offer a clinical perspective on the future role of vaccine therapies for cancer.