Androgen receptor mutations in patients with castration-resistant prostate cancer treated with apalutamide

Background

Mutations in the androgen receptor (AR) ligand-binding domain (LBD), such as F877L and T878A, have been associated with resistance to next-generation AR-directed therapies. ARN-509-001 was a phase I/II study that evaluated apalutamide activity in castration-resistant prostate cancer (CRPC). Here, we evaluated the type and frequency of 11 relevant AR-LBD mutations in apalutamide-treated CRPC patients.

Patients and methods

Blood samples from men with nonmetastatic CRPC (nmCRPC) and metastatic CRPC (mCRPC) pre- or post-abiraterone acetate and prednisone (AAP) treatment (≥6 months' exposure) were evaluated at baseline and disease progression in trial ARN-509-001. Mutations were detected in circulating tumor DNA using a digital polymerase chain reaction-based method known as BEAMing (beads, emulsification, amplification and magnetics) (Sysmex Inostics' GmbH).

Results

Of the 97 total patients, 51 had nmCRPC, 25 had AAP-naïve mCRPC, and 21 had post-AAP mCRPC. Ninety-three were assessable for the mutation analysis at baseline and 82 of the 93 at progression. The overall frequency of detected AR mutations at baseline was 7/93 (7.5%) and at progression was 6/82 (7.3%). Three of the 82 (3.7%) mCRPC patients (2 AAP-naïve and 1 post-AAP) acquired AR F877L during apalutamide treatment. At baseline, 3 of the 93 (3.2%) post-AAP patients had detectable AR T878A, which was lost after apalutamide treatment in 1 patient who continued apalutamide treatment for 12 months.

Conclusions

The overall frequency of detected mutations at baseline (7.5%) and progression (7.3%) using the sensitive BEAMing assay was low, suggesting that, based on this assay, AR-LBD mutations such as F877L and T878A are not common contributors to de novo or acquired resistance to apalutamide.

ClinicalTrials.gov identifier

NCT01171898.

Radiographic progression with nonrising PSA in metastatic castration-resistant prostate cancer: post hoc analysis of PREVAIL

BACKGROUND

Advanced prostate cancer is a phenotypically diverse disease that evolves through multiple clinical courses. PSA level is the most widely used parameter for disease monitoring, but it has well-recognized limitations. Unlike in clinical trials, in practice, clinicians may rely on PSA monitoring alone to determine disease status on therapy. This approach has not been adequately tested.

METHODS

Chemotherapy-naive asymptomatic or mildly symptomatic men (n=872) with metastatic castration-resistant prostate cancer (mCRPC) who were treated with the androgen receptor inhibitor enzalutamide in the PREVAIL study were analyzed post hoc for rising versus nonrising PSA (empirically defined as >1.05 vs ⩽1.05 times the PSA level from 3 months earlier) at the time of radiographic progression. Clinical characteristics and disease outcomes were compared between the rising and nonrising PSA groups.

RESULTS

Of 265 PREVAIL patients with radiographic progression and evaluable PSA levels on the enzalutamide arm, nearly one-quarter had a nonrising PSA. Median progression-free survival in this cohort was 8.3 months versus 11.1 months in the rising PSA cohort (hazard ratio 1.68; 95% confidence interval 1.26-2.23); overall survival was similar between the two groups, although less than half of patients in either group were still at risk at 24 months. Baseline clinical characteristics of the two groups were similar.

CONCLUSIONS

Non-rising PSA at radiographic progression is a common phenomenon in mCRPC patients treated with enzalutamide. As restaging in advanced prostate cancer patients is often guided by increases in PSA levels, our results demonstrate that disease progression on enzalutamide can occur without rising PSA levels. Therefore, a disease monitoring strategy that includes imaging not entirely reliant on serial serum PSA measurement may more accurately identify disease progression.

AZD3514, an oral selective androgen receptor down-regulator in patients with castration-resistant prostate cancer - results of two parallel first-in-human phase I studies

BACKGROUND

AZD3514 is a first-in-class, orally bio-available, androgen-dependent and -independent androgen receptor inhibitor and selective androgen-receptor down-regulator (SARD).

METHODS

In study 1 and 2, castration-resistant prostate cancer (CRPC) patients (pts) were initially recruited into a once daily (QD) oral schedule (A). In study 1, pharmacokinetic assessments led to twice daily (BID) dosing (schedule B) to increase exposure. Study 2 explored a once daily schedule.

RESULTS

In study 1, 49 pts were treated with escalating doses of AZD3514 (A 35 pts, B 14 pts). Starting doses were 100 mg (A) and 1000 mg (B). The AZD3514 formulation was switched from capsules to tablets at 1000 mg QD. 2000 mg BID was considered non-tolerable due to grade (G) 2 toxicities (nausea [N], vomiting [V]). No adverse events (AEs) met the dose-limiting toxicity (DLT) definition. Thirteen pts received AZD3514 in study 2, with starting doses of 250 mg QD. The most frequent drug-related AEs were N: G1/2 in 55/70 pts (79 %); G3 in 1 pt (1.4 %); & V: G1/2 in 34/70 pts (49 %) & G3 in 1 pt (1.4 %). PSA declines (≥50 %) were documented in 9/70 patients (13 %). Objective soft tissue responses per RECIST1.1 were observed in 4/24 (17 %) pts in study 1.

CONCLUSION

AZD3514 has moderate anti-tumour activity in pts with advanced CRPC but with significant levels of nausea and vomiting. However, anti-tumour activity as judged by significant PSA declines, objective responses and durable disease stabilisations, provides the rationale for future development of SARD compounds.

Ipilimumab alone or in combination with radiotherapy in metastatic castration-resistant prostate cancer: results from an open-label, multicenter phase I/II study

BACKGROUND

This phase I/II study in patients with metastatic castration-resistant prostate cancer (mCRPC) explored ipilimumab as monotherapy and in combination with radiotherapy, based on the preclinical evidence of synergistic antitumor activity between anti-CTLA-4 antibody and radiotherapy.

PATIENTS AND METHODS

In dose escalation, 33 patients (≥6/cohort) received ipilimumab every 3 weeks × 4 doses at 3, 5, or 10 mg/kg or at 3 or 10 mg/kg + radiotherapy (8 Gy/lesion). The 10-mg/kg cohorts were expanded to 50 patients (ipilimumab monotherapy, 16; ipilimumab + radiotherapy, 34). Evaluations included adverse events (AEs), prostate-specific antigen (PSA) decline, and tumor response.

RESULTS

Common immune-related AEs (irAEs) among the 50 patients receiving 10 mg/kg ± radiotherapy were diarrhea (54%), colitis (22%), rash (32%), and pruritus (20%); grade 3/4 irAEs included colitis (16%) and hepatitis (10%). One treatment-related death (5 mg/kg group) occurred. Among patients receiving 10 mg/kg ± radiotherapy, eight had PSA declines of ≥50% (duration: 3-13+ months), one had complete response (duration: 11.3+ months), and six had stable disease (duration: 2.8-6.1 months).

CONCLUSIONS

In mCRPC patients, ipilimumab 10 mg/kg ± radiotherapy suggested clinical antitumor activity with disease control and manageable AEs. Two phase III trials in mCRPC patients evaluating ipilimumab 10 mg/kg ± radiotherapy are ongoing. ClinicalTrials.gov identifier: NCT00323882.

Intermittent chemotherapy (ICh) for metastatic castration-resistant prostate cancer (mCRPC): Results of a prospective randomized phase II trial of the DoD Prostate Cancer Clinical Trials Consortium

133

Background: Docetaxel remains the standard of care for patients (pts) with mCRPC. However, the optimal duration of chemotherapy (Ch) is not known. Providing Ch holidays is often undertaken, but is not well characterized. A randomized phase II trial was undertaken to test two ICh regimens.

Methods: Pts with Ch naive mCRPC and KPS > 60% were eligible. Pts were treated with “induction” docetaxel 75 mg/m2 q3 weeks, and prednisone 5 mg po bid. After 6 cycles, responding pts (PSAWG1 criteria) stopped Ch and were randomized to observation (Obs) or to GM-CSF, 250 mcg/m2 sq daily for 14 days out of every 28 day cycle. Pts were followed with monthly PSA and imaging every 2 cycles until progressive disease (PD) by PSAWG1 criteria, at which point they resumed treatment with Ch, again for 6 cycles, followed by the same “off Ch” regimen. The primary endpoint was the time to PD while on Ch (time to Ch resistance.)

Results: Of 97enrolled pts to date, 94 are evaluable (3 are still undergoing induction). 69 pts completed induction (25 did not due to PD, adverse events (AE), or MD choice), of which 27 had PD after 6 cycles. Thus, 42/94 evaluable pts (45%) were eligible for randomization. Of these, 21 pts underwent Obs and 21 received GM-CSF. To date, 23/42 (55%) pts who underwent a Ch holiday restarted Ch, all for PSA PD. 8/23 (35%) had a response to Ch re-initiation. (15 pts did not re-start Ch because of AE, other therapy being started, or patient choice, and 4 pts are still undergoing either Obs or GM-CSF.) Obs pts were “off Ch” for a median of 2 months (range 2-4), compared with 3 months (range 2-8) for GM-CSF pts.

Conclusions: While feasible, only 45% of pts met criteria for ICh. 35% of pts responded to Ch re-initiation. Insufficient data exist to assess the impact of GM-CSF on time off Ch or time to Ch resistance.

No significant financial relationships to disclose.

A phase I/II randomized study of panobinostat and bicalutamide in castration-resistant prostate cancer (CRPC) patients progressing on second-line hormone therapy

156

Background: Aberrant expression and function of the androgen receptor (AR) is determinant of CRPC progression. We previously demonstrated that the histone-deacetylase inhibitor panobinostat (PAN) decreased AR levels and reversed resistance of androgen-independent AI-LNCaP and Rv1 cells to the antiandrogen bicalutamide (Bic). We designed a ph-I/II study to determine whether PAN would restore the sensitivity to Bic in CRPC patients (pts). We report the ph-I results evaluating safety and maximum tolerated dose (MTD) of Bic combined with oral, intermittent PAN.

Methods: Men with CRPC and limited bone metastasis, ECOG PS 0-2, PSA>2 ng/ml (or <2 + new metastases), adequate organ function and QTc<450 ms progressing on at least two prior hormones including antiandrogens were assigned each to one of 3 cohorts (C) for treatment with Bic 50 mg PO daily with oral PAN at 3 dose levels: C1, 20 mg tri-wkly (60 mg/wk) 2 of 3 wks; C2: 30 mg tri-wkly (90mg/wk) 2 of 3 wks, 40 mg PO tri-wkly (120mg/wk) 3 of 3 wks. Cycles (Cy) repeated every 21 days. Minimum treatment was 3 wks. Treatment could continue if clinical benefit. DLT were: grade (G) 3-4 febrile neutropenia >5 days and/or hospitalization; G3 thrombocytopenia with bleeding; QTcF>500 ms any G4 except nausea, vomiting, or diarrhea.

Results: Nine men, median (m) 65 yrs were treated in cohorts of three. mPSA at entry 9.26 ng/mL (IQR:8.24), mCy number, 6 (IQR: 5). MTD was not reached. All experienced some grade of toxicity attributable to PAN. Toxicity: no G4, only G3 was thrombocytopenia without bleeding in 3 pts (1 in C1, 2 in C3) that resolved spontaneously and controlled by dose reduction; G2: thrombocytopenia in 3, fatigue 2, high cholesterol 2, hypothyroidism 2; G1 thrombocytopenia in 2, fatigue 3, dyspepsia 3, anorexia 2. PSA decline ≥50% was achieved in 2 pts, stable PSA in 3 pts. Ph-II recommended PAN doses: Arm A: 40 mg tri-wkly (120 mg/wk) 2 of 3 wks; Arm B: 20 mg tri-wkly (60 mg/wk) 2 of 3wks with Bic 50 mg/daily.

Conclusions: Oral, intermittent PAN in combination with daily Bic is well tolerated in CRPC pts progressing on second line hormones and shows promising PSA responses suggesting anti-AR activity. Ph-II is ongoing.

[Table: see text]

The impact of DNA methylation on the identification of recurrent prostate cancer

21086

Purpose: Biochemical (PSA) recurrence of prostate cancer following radical prostatectomy remains a major problem. Better biomarkers are needed to identify high and low-risk patients. DNA methylation of promoter regions leads to gene silencing in many cancers. In this study, we assessed the impact of changes in DNA methylation on biochemical recurrence in men with prostate cancer. Methods: We examined the methylation status of fifteen genes using MSP (Methylation Specific PCR) on tissue samples from 151 patients with clinically localized prostate cancer for whom at least five years of follow-up after prostatectomy was available. Results: In a multivariable logistic regression analysis, extra capsular penetration, high Gleason score, and involvement of the lymph nodes, seminal vesicles, or surgical margin were associated with an increased risk of recurrence. In addition, samples with methylation of 2 specific genes involved in cell-cell adhesion and apoptosis were associated with biochemical recurrence with an odds ratio of 5.64 (95% CI=1.47–21.7, p=0.012) compared to samples without methylation of both of these genes. The methylation status of these 2 genes had a higher sensitivity (72.3%; 95% CI=57–84.4%) for detecting recurrences than all the clinico-pathological variables (p<0.02) except extra-capsular penetration (p=0.346). The methylation status of these 2 genes had a similar negative predictive value (79.0%; 95% CI=66.8–88.3%) as the individual clinico-pathological variables examined. Conclusion: DNA Methylation of specific genes is independently associated with an increased risk of biochemical recurrence after radical prostatectomy even one considers the prognostic clinico-pathologic variables used in the clinic today. Our findings should be validated on another larger group of patients with prostate cancer who have undergone radical prosatetectomies.

No significant financial relationships to disclose.