PARP Inhibitors in Prostate Cancer.

OPINION STATEMENT: The genomic landscape of metastatic prostate cancer (mPCa) reveals that up to 90% of patients harbor actionable mutations and >20% have somatic DNA repair gene defects (DRD). This provides the therapeutic rationale of PARP inhibition (PARPi) to achieve "synthetic lethality" in treating this fatal disease. Clinical trials with PARP inhibitors have shown significant response rates up to 88% for PCa patients having DRD like BRCA1/2 or ATM mutations. The FDA has awarded "breakthrough designation" to develop the PARPi olaparib in treating this subset of metastatic PCa patients. The search for predictive biomarkers has expanded the realm of DNA repair genetic defects and combination genetic platforms are being evaluated as tools to assess potential "BRCAness" of tumors. Ongoing clinical trials seek to determine the optimal timing and sequence of using these agents in current PCa treatment algorithms. Combination strategies of PARPi with chemo-, radiation, and hormonal therapies, targeted agents, and immunotherapy are promising avenues of current research. Multi-center international collaborations in well-designed biomarker-driven clinical trials will be key to harness the potential of PARPi in managing a heterogeneous disease like prostate cancer.

Practical guide to the use of enzalutamide.

INTRODUCTION: We summarize the development, definitive trials, and practical use of enzalutamide for practicing urologists and medical oncologists. The care paradigm for patients with metastatic castration resistant prostate cancer (mCRPC) is a changing landscape, with the ongoing discovery of drivers of cancer progression yielding actionable targets for drug development. Since 2010, sipuleucel-T, cabazitaxel, abiraterone with prednisone, radium 223 and enzalutamide have been Food and Drug Administration approved based upon improvement in overall survival in men with mCRPC. MATERIALS AND METHODS: A MEDLINE search for "enzalutamide or MDV3100" yielded 258 results. Prospective trials were reviewed. Abstracts from ASCO (American Society of Clinical Oncology) meetings and press release information were included where applicable. RESULTS: Enzalutamide, an oral inhibitor of the androgen receptor pathway, was approved in 2012 based upon improvement in overall survival of 4.8 months in men with mCRPC following docetaxel versus placebo. Measures of prostate-specific antigen (PSA) and radiographic response, and clinically significant endpoints such as quality of life improvement and toxicity parameters favored enzalutamide. Toxicity is modest with asthenia and fatigue being most common, with a 1% incidence of seizure reported, though patients can be selected to decrease this risk. CONCLUSION: Enzalutamide is an effective oral therapy for mCRPC, with an overall survival benefit before and following chemotherapy. Toxicity is mild, and seizure risk can be mitigated by careful patient selection. Ongoing studies will help determine the best sequence of novel agents for prostate cancer, along with safe and effective combinations of therapies. Better understanding of tumor characteristics, particularly reliance on the androgen receptor pathway, will lead to personalized approaches to prostate cancer therapy.

The rates of septicemia in older adults with prostate cancer treated with abiraterone or enzalutamide: A population-based study.

INTRODUCTION: Prostate cancer (PCa) is the most common non-cutaneous tumor among American men. Androgen receptor signaling inhibitors such as abiraterone and enzalutamide have been approved for similar disease states among patients with advanced PCa. Existing data suggest using steroids is associated with an increased risk of infection. Because abiraterone is usually prescribed with prednisone, we sought to compare the risk of septicemia in patients using abiraterone vs. enzalutamide. MATERIALS AND METHODS: We utilized the SEER-Medicare-linked data and used negative binomial regression models to compare the changes in the rates of septicemia-related hospitalizations six months pre- and post-abiraterone and enzalutamide initiation. RESULTS: We found that the incidence of septicemia-related hospitalizations increased 2.77 fold within six months of initiating abiraterone (incidence rate ratio [IRR]: 2.77, 95% confidence interval [CI]: 2.17-3.53) 1.97 fold within six months of starting enzalutamide (IRR: 1.97, 95% CI: 1.43-2.72). However, the difference in the changes did not reach statistical significance (interaction IRR: 0.71, 95% CI: 0.48-1.06). DISCUSSION: The findings suggest that both abiraterone and enzalutamide are associated with an increased risk of septicemia-related hospitalizations. However, the difference in the increase of septicemia risk following the two treatments did not reach statistical significance. Further studies are warranted to understand the mechanisms at play.

T-Cell redirecting bispecific antibodies: a review of a novel class of immuno-oncology for advanced prostate cancer.

Novel T-cell immunotherapies such as bispecific T-cell engagers (BiTEs) are emerging as promising therapeutic strategies for prostate cancer. BiTEs are engineered bispecific antibodies containing two distinct binding domains that allow for concurrent binding to tumor-associated antigens (TAAs) as well as immune effector cells, thus promoting an immune response against cancer cells. Prostate cancer is rich in tumor associated antigens such as, but not limited to, PSMA, PSCA, hK2, and STEAP1 and there is strong biologic rationale for employment of T-cell redirecting BiTEs within the prostate cancer disease space. Early generation BiTE constructs employed in clinical study have demonstrated meaningful antitumor activity, but challenges related to drug delivery, immunogenicity, and treatment-associated adverse effects limited their success. The ongoing development of novel BiTE constructs continues to address these barriers and to yield promising results in terms of efficacy and safety. This review will highlight some of most recent developments of BiTE therapies for patients with advanced prostate cancer and the evolving data surrounding BiTE constructs undergoing clinical evaluation.

Prognostic and predictive analyses of circulating plasma biomarkers in men with metastatic castration resistant prostate cancer treated with docetaxel/prednisone with or without bevacizumab.

BACKGROUND: CALGB 90401 (Alliance) was a phase III trial of 1050 patients with metastatic castration-resistant prostate cancer (mCRPC) comparing docetaxel, prednisone, bevacizumab (DP+B) versus DP alone. While this trial did not show an improvement in overall survival (OS), there were improved intermediate outcomes suggesting that subsets of men may derive benefit from this combination. The purpose of this analysis was to identify prognostic and predictive biomarkers associated with OS and progression-free survival (PFS) benefit from DP+B. METHODS: Baseline EDTA plasma samples from 650 consenting patients were analyzed for 24 biomarkers. The proportional hazards model was utilized to test for the prognostic and predictive importance of the biomarkers for OS. The statistically significant biomarkers of OS were further investigated for prognostic and predictive importance for other secondary outcomes. RESULTS: 15 markers [ICAM-1, VEGF-R3, TIMP-1, TSP-2, Ang-2, Her-3, Osteopontin (OPN), PlGF, VCAM-1, HGF, VEGF, Chromogranin A, IL-6, VEGF-R1, BMP-9] were prognostic of OS, while 9 markers (ICAM-1, VEGF-R3, Her-3, TIMP-1, Ang-2, OPN, PlGF, HGF, and VEGF) were also prognostic of PFS. All markers were statistically significant in univariate analyses after adjustment for multiplicity (FDR < 0.1). In multivariable analyses of OS adjusting for risk score, seven markers had FDR < 0.1, including ICAM-1, VEGF-R3, TIMP-1, Ang-2, VEGF, TSP-2 and HGF. In unadjusted analysis, OPN was predictive of PFS improvement with DP+B, in both univariate and multivariable analysis. However, none of the biomarkers tested were predictive of clinical outcomes after adjusting for multiple comparisons. CONCLUSIONS: Multiple biomarkers were identified in CALGB 90401 as prognostic of clinical outcomes but not predictive of OS. While OPN may have promise as a potential biomarker for anti-angiogenic therapies, further mechanistic and clinical studies are needed to determine the underlying biology and potential clinical application.

Predictors of consenting to participate in a clinical trial among urban cancer patients.

BACKGROUND: Patient participation in clinical trials is influenced by demographic and other individual level characteristics. However, there is less research on the role of geography and neighborhood-level factors on clinical trial participation. This study identifies the demographic, clinical, geographic, and neighborhood predictors of consenting to a clinical trial among cancer patients at a large, urban, NCI-designated cancer center in the Mid-Atlantic region. METHODS: We used demographic and clinical data from patients diagnosed with cancer between 2015 and 2017. We geocoded patient addresses and calculated driving distance to the cancer center. Additionally, we linked patient data to neighborhood-level educational attainment, social capital and cancer prevalence. Finally, we used generalized linear mixed-effects conditional logistic regression to identify individual and neighborhood-level predictors of consenting to a clinical trial. RESULTS: Patients with higher odds of consenting to trials were: Non-Hispanic White, aged 50-69, diagnosed with breast, GI, head/neck, hematologic, or certain solid tumor cancers, those with cancers at regional stage, never/former tobacco users, and those with the highest neighborhood social capital index. Patients who lived further from the cancer center had higher odds of consenting to a trial. With every 1-km increase in residential distance, there was a 4% increase in the odds that patients would consent to a trial. Neither of the additional neighborhood-level variables predicted consenting to a clinical trial. CONCLUSIONS: This study identifies important demographic, patient-level, and geographic factors associated with consenting to cancer clinical trials, and lays the groundwork for future research exploring the role of neighborhood-level factors in clinical trial participation.

Phase I Study of Niraparib in Combination with Radium-223 for the Treatment of Metastatic Castrate-Resistant Prostate Cancer.

PURPOSE: To identify the safety of niraparib, a PARP inhibitor, in combination with Radium-223 for the treatment of metastatic castrate-resistant prostate cancer (mCRPC) in men without known BRCA mutations. PATIENTS AND METHODS: Men with progressive mCPRC following ≥1 line of androgen receptor (AR)-targeted therapy and bone metastases but no documented BRCA-1 or BRCA-2 alterations or bulky visceral disease were included. Niraparib dose was escalated in combination with standard dosing of Radium-223 using a time-to-event continual reassessment method. The highest dose level with a DLT probability <20% was defined as MTD. Secondary endpoints included PSA change and progression-free survival. Exploratory analyses included assessing DNA mutations found in ctDNA as well as gene expression changes assessed in whole blood samples. RESULTS: Thirty patients were treated with niraparib and radium-223: 13 patients received 100 mg, 12 received 200 mg, and 5 patients received 300 mg of niraparib. There were six DLT events: two (13%) for neutropenia, two (13%) for thrombocytopenia, whereas fatigue and nausea each occurred once (3%). Anemia (2/13%) and neutropenia (2/13%) were the most common grade 3 adverse events. For patients with prior chemotherapy exposure, the MTD was 100 mg, whereas the MTD for chemotherapy naïve patients was 200 mg. Whole blood gene expression of PAX5 and CD19 was higher in responders and ARG-1, IL2R, and FLT3 expression was higher in nonresponders. CONCLUSIONS: Combining niraparib with Radium-223 in patients with mCRPC was safe; however, further studies incorporating biomarkers will better elucidate the role of combinations of PARP inhibitors with DNA damaging and other agents.

PARP inhibition and pharmacological ascorbate demonstrate synergy in castration-resistant prostate cancer.

Prostate cancer (PCa) is the second leading cause of cancer death for men in the United States. While organ-confined disease has reasonable expectation of cure, metastatic PCa is universally fatal upon recurrence during hormone therapy, a stage termed castration-resistant prostate cancer (CRPC). Until such time as molecularly defined subtypes can be identified and targeted using precision medicine, it is necessary to investigate new therapies that may apply to the CRPC population as a whole. The administration of ascorbate, more commonly known as ascorbic acid or Vitamin C, has proved lethal to and highly selective for a variety of cancer cell types. There are several mechanisms currently under investigation to explain how ascorbate exerts anti-cancer effects. A simplified model depicts ascorbate as a pro-drug for reactive oxygen species (ROS), which accumulate intracellularly and generate DNA damage. It was therefore hypothesized that poly(ADP-ribose) polymerase (PARP) inhibitors, by inhibiting DNA damage repair, would augment the toxicity of ascorbate. Results: Two distinct CRPC models were found to be sensitive to physiologically relevant doses of ascorbate. Moreover, additional studies indicate that ascorbate inhibits CRPC growth in vitro via multiple mechanisms including disruption of cellular energy dynamics and accumulation of DNA damage. Combination studies were performed in CRPC models with ascorbate in conjunction with escalating doses of three different PARP inhibitors (niraparib, olaparib, and talazoparib). The addition of ascorbate augmented the toxicity of all three PARP inhibitors and proved synergistic with olaparib in both CRPC models. Finally, the combination of olaparib and ascorbate was tested in vivo in both castrated and non-castrated models. In both cohorts, the combination treatment significantly delayed tumor growth compared to monotherapy or untreated control. Conclusions: These data indicate that pharmacological ascorbate is an effective monotherapy at physiological concentrations and kills CRPC cells. Ascorbate-induced tumor cell death was associated with disruption of cellular energy dynamics and accumulation of DNA damage. The addition of PARP inhibition increased the extent of DNA damage and proved effective at slowing CRPC growth both in vitro and in vivo. These findings nominate ascorbate and PARPi as a novel therapeutic regimen that has the potential to improve CRPC patient outcomes.

Substantial Gleason reclassification in Black men with national comprehensive cancer network low-risk prostate cancer - A propensity score analysis.

BACKGROUND: Emerging evidence suggests that a subset of Black men with National Comprehensive Cancer Network (NCCN) low-risk prostate cancer (PCa) may harbor high volume and genomically aggressive disease. However, limited, and ambiguous research exist to evaluate the risk of extreme Gleason reclassification in Black men with low-risk PCa. METHODS: This retrospective cohort study included 45,674 low-risk PCa patients who underwent prostatectomy and were not on active surveillance, from National Cancer Database (NCDB). A propensity score matched-pair design was employed, and the final cohort was limited to 1:1 matched 12,340 patients. Gleason score reclassification was used as primary endpoint. As such, any migration to pathologic Gleason score ≥7(3 + 4) was identified as overall, whereas migration to ≥7(4 + 3) was defined as extreme reclassification. A conditional Poisson regression model was used to estimate the risk of reclassification. Whereas spline model was used to estimate the impact of increasing time to treatment as a non-linear function on Gleason reclassification between race group. RESULTS: Upon matching there were no differences in the baseline characteristics between race groups. In a matched cohort, higher proportion of low-risk Black men (6.6%) reported extreme reclassification to pathologic Gleason score than White men (5.0%), p < 0.001. In a conditional Poisson regression model adjusted for time to treatment, the risk of overall (RR = 1.09, 95% CI, 1.05-1.13, p < 0.001) and extreme (RR = 1.30, 95% CI, 1.12-1.50, p = 0.004) reclassification was significantly higher in Black men as compared to their White counterpart. In spline model, the probability of Gleason reclassification in Black men was elevated with increasing time to treatment, especially after 180 days (53% vs. 43% between Black and White men). CONCLUSION: Risk of Gleason score reclassification is disparately elevated in Black men with low-risk PCa. Furthermore, time to treatment can non-linearly impact Gleason reclassification in Black men.

Screening for prostate cancer: the current evidence and guidelines controversy.

INTRODUCTION: Prostate cancer presents a global public health dilemma. While screening with prostate specific antigen (PSA) has led to more men diagnosed with prostate cancer than in previous years, the potential for negative effects from over-diagnosis and treatment cannot be ignored. MATERIALS AND METHODS: We reviewed Medline for recent articles that discuss clinical trials, evidence based recommendations and guidelines from major medical organizations in the United States and worldwide concerning prostate cancer screening. RESULTS: Results from the European Randomized Screening for Prostate Cancer (ERSPC), the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, and Göteborg Swedish trials regarding prostate screening are controversial with the ERSPC and Göteborg showing a reduction in prostate cancer mortality and the PLCO trial showing no benefit. Recommendations from the American Urological Association (AUA), Japanese Urological Association (JUA), and National Comprehensive Cancer Network (NCCN) have recommended that all men obtain a baseline PSA beginning at age 40. The American Cancer Society (ACS) stratifies screening recommendations based on age and risk, but states that screening should take place only after an informed discussion between provider and patient. The United States Preventative Health Service Task Force (USPSTF) states that evidence is insufficient to assess the risks and benefits of prostate cancer screening in men younger than 75 years. Other major international health organizations offer a similar reserved approach or recommend against screening for prostate cancer. Most groups indicate that screening to determine who should undergo prostate biopsy typically includes both a serum PSA and digital rectal examination, with the latest ACS publications noting that the rectal exam is optional. A common theme from all groups is that an informed discussion with the patients is strongly recommended and that screening does increase the number of men diagnosed with non-metastatic, early disease. CONCLUSIONS: Prostate cancer screening guidelines vary widely between countries and between different medical organizations within individual countries including the United States. Further, the evidence for and against prostate cancer screening remains highly controversial. Longitudinal follow up of completed screening trials is ongoing and may yield additional findings as the time course of prostate cancer outcomes can be protracted. The literature controversy suggests that no standard of care exists for prostate cancer screening today. Until there is agreement in guidelines between major professional organizations who have weighed in on this topic, patients and physicians should be encouraged to consider engaging in shared and informed decision process concerning screening for prostate cancer.

New and topics: enfortumab vedotin mechanisms of response and resistance in urothelial cancer - What do we understand so far?

Enfortumab vedotin (EV) was FDA approved in December 2019 for platinum- and checkpoint-refractory urothelial cancer based on an exceptional 44% response rate, and is currently approved for use after platinum and checkpoint inhibitor therapy. Enfortumab is an antibody-drug conjugate that targets Nectin-4, which is widely expressed in urothelial cancer. Despite this ample target, clinical benefit is not achieved by all patients, and mechanisms of treatment resistance are undescribed. Herein we summarize what is known to date regarding coorelative findings and subgroup analysis and EV response, including novel biopsy data in patients with tumor progression post EV.

A Randomized Phase II Study of Androgen Deprivation Therapy with or without Palbociclib in RB-positive Metastatic Hormone-Sensitive Prostate Cancer.

PURPOSE: Palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, blocks proliferation in a RB and cyclin D-dependent manner in preclinical prostate cancer models. We hypothesized that cotargeting androgen receptor and cell cycle with palbociclib would improve outcomes in patients with metastatic hormone-sensitive prostate cancer (mHSPC). PATIENTS AND METHODS: A total of 60 patients with RB-intact mHSPC were randomized (1:2) to Arm 1: androgen deprivation (AD) or Arm 2: AD + palbociclib. Primary endpoint was PSA response rate (RR) after 28 weeks of therapy. Secondary endpoints included safety, PSA, and clinical progression-free survival (PFS), as well as PSA and radiographic RR. Tumors underwent exome sequencing when available. Circulating tumor cells (CTC) were enumerated at various timepoints. RESULTS: A total of 72 patients with mHSPC underwent metastatic disease biopsy and 64 had adequate tissue for RB assessment. A total of 62 of 64 (97%) retained RB expression. A total of 60 patients initiated therapy (Arm 1: 20; Arm 2: 40). Neutropenia was the most common grade 3/4 adverse event in Arm 2. Eighty percent of patients (Arm 1: 16/20, Arm 2: 32/40; P = 0.87) met primary PSA endpoint ≤4 ng/mL at 28 weeks. PSA undetectable rate at 28 weeks was 50% and 43% in Arms 1 and 2, respectively (P = 0.5). Radiographic RR was 89% in both arms. Twelve-month biochemical PFS was 69% and 74% in Arms 1 and 2, respectively (P = 0.72). TP53 and PIK3 pathway mutations, 8q gains, and pretreatment CTCs were associated with reduced PSA PFS. CONCLUSIONS: Palbociclib did not impact outcome in RB-intact mHSPC. Pretreatment CTC, TP53 and PIK3 pathway mutations, and 8q gain were associated with poor outcome.

MAPK Reliance via Acquired CDK4/6 Inhibitor Resistance in Cancer.

Purpose: Loss of cell-cycle control is a hallmark of cancer, which can be targeted with agents, including cyclin-dependent kinase-4/6 (CDK4/6) kinase inhibitors that impinge upon the G1-S cell-cycle checkpoint via maintaining activity of the retinoblastoma tumor suppressor (RB). This class of drugs is under clinical investigation for various solid tumor types and has recently been FDA-approved for treatment of breast cancer. However, development of therapeutic resistance is not uncommon.Experimental Design: In this study, palbociclib (a CDK4/6 inhibitor) resistance was established in models of early stage, RB-positive cancer.Results: This study demonstrates that acquired palbociclib resistance renders cancer cells broadly resistant to CDK4/6 inhibitors. Acquired resistance was associated with aggressive in vitro and in vivo phenotypes, including proliferation, migration, and invasion. Integration of RNA sequencing analysis and phosphoproteomics profiling revealed rewiring of the kinome, with a strong enrichment for enhanced MAPK signaling across all resistance models, which resulted in aggressive in vitro and in vivo phenotypes and prometastatic signaling. However, CDK4/6 inhibitor-resistant models were sensitized to MEK inhibitors, revealing reliance on active MAPK signaling to promote tumor cell growth and invasion.Conclusions: In sum, these studies identify MAPK reliance in acquired CDK4/6 inhibitor resistance that promotes aggressive disease, while nominating MEK inhibition as putative novel therapeutic strategy to treat or prevent CDK4/6 inhibitor resistance in cancer. Clin Cancer Res; 24(17); 4201-14. ©2018 AACR.

PARP-1 regulates DNA repair factor availability.

PARP-1 holds major functions on chromatin, DNA damage repair and transcriptional regulation, both of which are relevant in the context of cancer. Here, unbiased transcriptional profiling revealed the downstream transcriptional profile of PARP-1 enzymatic activity. Further investigation of the PARP-1-regulated transcriptome and secondary strategies for assessing PARP-1 activity in patient tissues revealed that PARP-1 activity was unexpectedly enriched as a function of disease progression and was associated with poor outcome independent of DNA double-strand breaks, suggesting that enhanced PARP-1 activity may promote aggressive phenotypes. Mechanistic investigation revealed that active PARP-1 served to enhance E2F1 transcription factor activity, and specifically promoted E2F1-mediated induction of DNA repair factors involved in homologous recombination (HR). Conversely, PARP-1 inhibition reduced HR factor availability and thus acted to induce or enhance "BRCA-ness". These observations bring new understanding of PARP-1 function in cancer and have significant ramifications on predicting PARP-1 inhibitor function in the clinical setting.

Pharmacokinetics and toxicity of weekly docetaxel in older patients.

PURPOSE: To evaluate the pharmacokinetics of weekly docetaxel in a cohort of older patients with metastatic cancer and to explore the relationship of pharmacokinetic variables, Erythromycin Breath Test results, age, geriatric assessment variables, and toxicity to therapy. EXPERIMENTAL DESIGN: Twenty patients ages > or = 65 years with metastatic breast, prostate, or lung cancer entered an Institutional Review Board-approved protocol to evaluate the pharmacokinetics of weekly docetaxel administered at 35 mg/m2 i.v. for 3 weeks followed by a 1-week break. The Erythromycin Breath Test and geriatric assessment were done before the first dose. Blood samples were collected for pharmacokinetic analysis with the first dose of docetaxel. RESULTS: Of the 20 patients who entered the study, 19 were evaluable. There were no age-related differences in the pharmacokinetics of weekly docetaxel. Fifty-eight percent (11 of 19) experienced grade > or = 3 toxicity: 16% (3 of 19) grade > or = 3 hematologic toxicity, and 53% (10 of 19) grade > or = 3 nonhematologic toxicity. There was an association between the Erythromycin Breath Test results and docetaxel pharmacokinetic variables; however, there was no association between Erythromycin Breath Test results or docetaxel pharmacokinetics with frequency of grade > or = 3 toxicity. CONCLUSIONS: Despite no statistically significant age-related differences in weekly docetaxel pharmacokinetics, over half of these older patients experienced a grade > or = 3 toxicity at the 35 mg/m2 starting dose. We advocate a starting dose of 26 mg/m2 on this weekly schedule and dose escalating if no toxicity.

Trial Design and Objectives for Castration-Resistant Prostate Cancer: Updated Recommendations From the Prostate Cancer Clinical Trials Working Group 3.

PURPOSE: Evolving treatments, disease phenotypes, and biology, together with a changing drug development environment, have created the need to revise castration-resistant prostate cancer (CRPC) clinical trial recommendations to succeed those from prior Prostate Cancer Clinical Trials Working Groups. METHODS: An international expert committee of prostate cancer clinical investigators (the Prostate Cancer Clinical Trials Working Group 3 [PCWG3]) was reconvened and expanded and met in 2012-2015 to formulate updated criteria on the basis of emerging trial data and validation studies of the Prostate Cancer Clinical Trials Working Group 2 recommendations. RESULTS: PCWG3 recommends that baseline patient assessment include tumor histology, detailed records of prior systemic treatments and responses, and a detailed reporting of disease subtypes based on an anatomic pattern of metastatic spread. New recommendations for trial outcome measures include the time to event end point of symptomatic skeletal events, as well as time to first metastasis and time to progression for trials in the nonmetastatic CRPC state. PCWG3 introduces the concept of no longer clinically benefiting to underscore the distinction between first evidence of progression and the clinical need to terminate or change treatment, and the importance of documenting progression in existing lesions as distinct from the development of new lesions. Serial biologic profiling using tumor samples from biopsies, blood-based diagnostics, and/or imaging is also recommended to gain insight into mechanisms of resistance and to identify predictive biomarkers of sensitivity for use in prospective trials. CONCLUSION: PCWG3 moves drug development closer to unmet needs in clinical practice by focusing on disease manifestations most likely to affect prognosis adversely for therapeutics tested in both nonmetastatic and metastatic CRPC populations. Consultation with regulatory authorities is recommended if a trial is intended to seek support for drug approval.

Phase I clinical trial of histone deacetylase inhibitor: suberoylanilide hydroxamic acid administered intravenously.

PURPOSE: To evaluate the safety, pharmacokinetics, and biological activity of suberoylanilide hydroxamic acid (SAHA) administered by 2-h i.v. infusion in patients with advanced cancer. EXPERIMENTAL DESIGN: SAHA was administered for 3 days every 21 days in part A and 5 days for 1-3 weeks in part B. Dose escalation proceeded independently in patients with solid tumor and hematological malignancies (part B only). Pharmacokinetic studies were performed along with assessment of acetylated histones in peripheral blood mononuclear cells and tumor tissues. RESULTS: No dose-limiting toxicities were observed in 8 patients enrolled in part A (75, 150, 300, 600, and 900 mg/m(2)/day). Among 12 hematological and 17 solid tumor patients enrolled in part B (300, 600, and 900 mg/m(2)/day), therapy was delayed > or = 1 week for grade 3/4 leukopenia and/or thrombocytopenia in 2 of 5 hematological patients at 600 mg/m(2)/day x 5 days for 3 weeks. The maximal-tolerated dose was 300 mg/m(2)/day x 5 days for 3 weeks for hematological patients. One solid patient on 900 mg/m(2)/day x 5 days for 3 weeks developed acute respiratory distress and grade 3 hypotension. The cohort was expanded to 6 patients, and no additional dose-limiting toxicities were observed. Mean terminal half-life ranged from 21 to 58 min, and there was dose-proportional increase in area under the curve. An accumulation of acetylated histones in peripheral blood mononuclear cells up to 4 h postinfusion was observed at higher dose levels. Posttherapy tumor biopsies showed an accumulation of acetylated histones by immunohistochemistry. Four (2 lymphoma and 2 bladder) patients had objective tumor regression with clinical improvement in tumor related symptoms. CONCLUSIONS: Daily i.v. SAHA is well tolerated, inhibits the biological target in vivo, and has antitumor activity in solid and hematological tumors.

CCR 20th Anniversary Commentary: Vorinostat-Gateway to Epigenetic Therapy.

The study by Kelly and colleagues, published in the September 1, 2003, issue of Clinical Cancer Research, established the safety and biologic activity of the first-in-class histone deacetylase inhibitor, vorinostat, which was administered intravenously. Subsequent studies led to the development of oral vorinostat and the regulatory approval of vorinostat for cutaneous T-cell lymphomas, which opened the door for the next generation of inhibitors.