Antibiotic therapy and association with oncological outcomes from targeted and immune-based therapy in hepatocellular carcinoma (HCC)

4089

Background: Immune checkpoint inhibitors (ICI) alone or in combination with tyrosine kinase (TKI) or VEGF pathway inhibitors (VEGFi) are therapeutic options in unresectable HCC (uHCC). Whether exposure to antibiotics (ATB), a consolidated adverse prognostic factor in ICI recipients, affects outcome in HCC remains unclear. Methods: FDA analysed patient-level data of 4098 patients receiving ICI (n = 842) either as monotherapy (n = 258) or combinations (n = 584), TKI (N = 1968), VEGFi (n = 480) or placebo (n = 808) as part of 9 international clinical trials submitted to the US Food and Drug Administration in support of marketing applications. Associations for ATB exposure within 30 days before or after initiation of anti-cancer treatment (ATB) with overall (OS) and progression-free survival (PFS) were examined across therapeutic modality. Estimates were weighted by propensity score (PSW) using clinically relevant covariates. Results: Out of 4098 patients with uHCC mostly secondary to Hepatitis B (39%) or C (21%) infection, the majority were males (83%) with a median age of 64 (range 18-88), ECOG performance status of 0 (60%) and Child-Pugh A class (98%). Most patients had metastases (68%) but did not have macrovascular invasion (71%). Overall, 620 patients (15%) were ATB+, with comparable rates across placebo (12%), TKI (16%), VEGFi (15%), and ICI (16%). In the overall population, ATB was associated with shorter PFS (2.8 vs 3.9 months [m], HR 1.29, 95%CI 1.22-1.36) and OS (6.4 vs. 8.8 m; HR 1.36, 95%CI 1.29-1.43). In PSW analyses, ATB was associated with shorter PFS in patients treated with ICI (HR 1.52, 95%CI 1.34-1.73), TKI (HR 1.29, 95%CI 1.19-1.39) and placebo (HR 1.23, 95%CI 1.11-1.37). Similar results were observed in PSW analyses of OS in patients treated with ICI (HR 1.22, 95%CI 1.08-1.38), TKI HR 1.40, 95%CI 1.30-1.52), and placebo (HR 1.40, 95%CI 1.25-1.57). Consistent outcomes were observed for ATB+ patients within ICI treatment subgroups, including patients treated with anti-PD-1 monotherapy (PFS HR 1.49, 95%CI 1.22-1.80; OS HR 1.31 1.02-1.68) and ICI combinations (PFS HR 1.50, 95%CI 1.26-1.77; OS HR 1.14 0.99-1.32). Conclusions: Unlike other oncological indications where the detrimental effect of ATB may be more prominent in ICI recipients, ATB is associated with inferior outcomes across a broad range of anti-cancer therapies for HCC and placebo. Whether ATB is causally linked to worse outcomes through disruption of the gut liver axis remains to be demonstrated in translational studies.

Treatment-related toxicity and improved outcomes with immune checkpoint inhibitors in patients with hepatocellular carcinoma

4085

Background: The development of treatment-related adverse events (trAE) correlates favorably with clinical outcomes in multiple studies of patients receiving immune checkpoint inhibitors (ICI), however, this relationship is undefined in patients with hepatocellular carcinoma (HCC). This retrospective multi-center study aimed to examine whether trAEs are prognostic in HCC. Methods: We established an international consortium of 10 tertiary-care referral centers located in Europe (n = 67), United States (US, n = 248) and Asia (n = 42) to test whether the development of clinically significant trAE (i.e. graded >2, trAE2) predicted for improved overall (OS), progression-free survival (PFS), and overall response rates (ORR) following ICI, and subsequently validated this association in a separate cohort of 406 HCC patients receiving ICI therapy as part of international clinical trials submitted to the US Food and Drug Administration (FDA) in support of marketing applications. Results: In a multi-institutional cohort of 357 patients, 274 (77%) with Barcelona Clinic Liver Cancer (BCLC) stage C HCC mostly treated with ICI monotherapy (n = 304, 85%), trAE were reported in 146 patients (41%). Development of trAE2 were associated with longer OS (23.3 versus 12.2 months) and PFS (8.6 months versus 3.7 months). After adjusting for viral aetiology, gender, presence of cirrhosis, Child-Pugh class, BCLC stage, AFP levels, ECOG-PS, ICI regimen (mono/combination therapy) and receipt of corticosteroid therapy, trAE2 were confirmed predictors of improved OS (HR 0.55; 95%CI:0.34-0.88) and PFS (HR 0.51; 95%CI: 0.35-0.74). TrAE2 were associated with higher ORR (27% versus 16%) from ICI. The association between trAE2 and patients’ OS (HR 0.49; 95%CI:0.34-0.70) and PFS (HR 0.43; 95%CI:0.32-0.59) was also observed in the FDA dataset. After a 6-weeks landmark selection, trAE2 were confirmed to be associated with improved PFS (HR 0.59; 95%CI:0.39-0.87); the additional analysis adjusted for tumour response and duration of treatment within the FDA cohort further confirmed the association with longer PFS (HR 0.67; 95%CI: 0.47-0.94). Conclusions: Development of trAE2 may correlate with response and survival in patients with HCC receiving ICI, a clinical setting where the lack of biomarkers still represents an unmet need. Prospective studies aimed at understanding the underlying immunologic foundations of such relationship are warranted to identify predictive biomarkers of toxicity and response.

A Food and Drug Administration analysis of survival outcomes comparing the Adjuvant Paclitaxel and Trastuzumab trial with an external control from historical clinical trials

BACKGROUND

Although the Adjuvant Paclitaxel and Trastuzumab (APT) trial has been adopted clinically, single-arm trials have limitations, and interest remains whether these patients with small node-negative human epidermal growth factor receptor 2 (HER2)-positive early breast cancer (EBC) would benefit from more intensive chemotherapy. This analysis explored whether external controls can contextualize single-arm studies to add to clinical decision making in the use of de-escalated therapy in patients with low-risk HER2-positive EBC.

PATIENTS AND METHODS

Patient-level data from five randomized trials supporting drug approval in adjuvant HER2-positive EBC were pooled, and patients with low-risk EBC were selected (n = 1770). Patients treated concurrently with trastuzumab and either anthracycline/cyclophosphamide/taxane/trastuzumab (ACTH) or taxane/carboplatin/trastuzumab (TCH; n = 1366) were matched (1:1) to patients treated with paclitaxel and trastuzumab (TH) in the APT trial (n = 406) using propensity scores. Patients treated with anthracycline/cyclophosphamide/taxane (ACT; n = 374) were also matched (1:1) to those treated with TH. Propensity scores were estimated using covariates of age, tumor stage, estrogen receptor status, progesterone receptor status, and histological grade.

RESULTS

After matching, the estimated probabilities of invasive disease-free survival (iDFS) at 3 and 5 years were 98.6% and 96.5% in the TH arm, and 96.6% and 92.9% in the ACTH/TCH arm, respectively. The estimated probabilities of overall survival (OS) at 3 and 5 years were 99.7% and 99.3% in the TH arm, and 99.0% and 97.4% in the ACTH/TCH arm, respectively. Comparing the TH arm with the ACT arm in the matched sample, the estimated difference in iDFS was 7.5% (TH 98.8% and ACT 91.3%) at 3 years and 12.6% (TH 96.1% and ACT 83.5%) at 5 years. The estimated difference in OS was 2.6% (TH 100% and ACT 97.4%) at 3 years, and 5.3% (TH 99.3% and ACT 94.0%) at 5 years.

CONCLUSIONS

Our analyses suggest that patients' outcomes in both arms were in general similar, thus providing additional reassurance regarding de-escalation of therapy.

FDA pooled analysis of time to treatment discontinuation (TTD) in frontline advanced renal cell carcinoma trials

5081

Background: Time to treatment discontinuation (TTD) has been proposed as a potential pragmatic real-world data (RWD) endpoint, and was closely correlated with progression-free survival (PFS) in pooled analyses of non-small cell lung cancer (NSCLC) and breast cancer trials across therapeutic classes (Blumenthal, Ann Onc 2019; Gao, SABCS Abstract P5-14-02). Methods: We analyzed data from all randomized patients (pts) in the phase 3 trials submitted to FDA 2016-18 evaluating a combination therapy (Rx) of an immuno-oncology agent and another systemic Rx (IO-X) versus sunitinib (SUN) for treatment-naïve advanced renal cell carcinoma (RCC). Protocols specified treatment until progression, but treatment beyond progression was allowed. TTD was defined as the time from the start of Rx to time of treatment discontinuation of both drugs in combination Rx or SUN. We measured TTD in treatment-defined subgroups (IO-X and SUN) and across all pts, and pt-level correlation (Pearson’s r) between TTD and PFS and between TTD and overall survival (OS). We also determined rates of disparity between TTD and PFS greater than 3 months. Results: Of 3758 pts (IO-X, n=1878; SUN, n=1880), 3190 pts (85%) had a TTD event, and 1899 pts (51%) had a PFS event. Median TTD was longer among pts receiving IO-X than SUN (12.3 versus 8.0 months). Regardless of drug class, more pts had early (TTD shorter than PFS by ≥ 3 months) TTD events than late TTD (13.4% versus 6.4%, overall). We found higher correlation between TTD and PFS in pts receiving SUN ( r = 0.89) than pts receiving IO-X ( r = 0.72). Overall, TTD was more closely associated with PFS ( r = 0.80) than with OS (0.61). Conclusions: Observed correlations of TTD to PFS were stronger compared to the correlation of TTD to OS. This may be expected because OS is farther removed in time from TTD than is PFS. In contrast to TTD in NSCLC, more than twice as many pts in RCC trials had early TTD than late TTD, regardless of Rx group, which may indicate earlier discontinuation with combination Rx due to additive toxicity. Limitations include the censoring of PFS and OS and the post-hoc nature of this analysis. [Table: see text]

An FDA analysis of the association of tumor growth rate and overall and progression-free survival in metastatic non-small cell lung cancer (NSCLC) patients

9541

Background: Previous studies have suggested that tumor growth rate (g), estimated using prostate-specific antigen values, is associated with overall survival (OS) in prostate cancer (Wilkerson, 2016). We performed a retrospective pooled analysis in non-small cell lung cancer (NSCLC) to investigate the extent to which g values estimated using radiological tumor measurements in clinical trials are associated with survival. Methods: We identified 24 randomized clinical trials submitted to FDA between 2013 and 2019 investigating either immune checkpoint inhibitor (ICI) or targeted therapy (TT) in pts with metastatic NSCLC. Of 9934 patients (pts) enrolled, 5532 pts (2401, 1189, and 1942 pts treated with ICI, TT, and chemotherapy respectively) had sufficient data to derive a valid g. The g was evaluated by both type and line of therapy. Pts were then grouped according to quartiles of g, with Q1 being the lowest. We calculated OS and progression-free survival (PFS) for each group via the Kaplan-Meier method, and used the Cox model for group comparison. Results: Median g was 9.7E-4, 1.4E-3, and 2.2E-3/day, and median OS was 34.2, 21.3, and 15.3 months (mo), in pts treated with TT, ICI, and chemotherapy, respectively, regardless of lines of therapy. When treated with the same type of therapy, pts receiving 2nd line therapy had a higher median g than those receiving 1st line. The median survival and log-rank hazard ratios for pts treated with 1st line ICI monotherapy are shown in the Table. Conclusions: TT is associated with the lowest median g, followed by ICI, and then chemotherapy, perhaps due to patient selection, better inherent biology/natural history, or favorable results of TT on selected tumors. Regardless, we found that g is inversely associated with survival, across treatment types. This relationship is also observed in pts treated with the same type and line of therapy (for example, 1st line ICI), where Q1 has the longest survival, followed by Q2, Q3, and then Q4. In summary, our exploratory analysis suggests that g derived from radiological tumor measurements in NSCLC may relate to survival. Prospective studies are needed to evaluate if g might be an earlier endpoint compared to classical response criteria. [Table: see text]

Outcomes in patients with advanced non-small cell lung cancer (aNSCLC) and high PD-L1 expression treated with immune checkpoint inhibitor monotherapy: An FDA-pooled analysis

9606

Background: Higher PD-L1 score ≥ 50% predicts for greater benefit to immune checkpoint inhibitor (ICI) therapy in first line (1L) treatment of aNSCLC. It has recently been reported that PD-L1 score ≥ 90% predicts for even greater benefit to 1L ICI monotherapy (Aguilar et al., 2019). We examined pooled clinical trial databases to examine the relationship between high PD-L1 expression across multiple ICI monotherapies in 1L and second line (2L) treatment of aNSCLC. Methods: Data was pooled from trials (five 1L and five 2L) of ICI for the treatment of patients with aNSCLC. We defined PD-L1 score as the proportion of tumor cell stained by the assay (total of four assays identified) and included patients in the analysis with PD-L1 score ≥ 50%. Tumor-infiltrating immune cell staining was not considered. Progression-free survival (PFS) and overall survival (OS) by line of therapy for patients with PD-L1 score ≥ 90% and patients with PD-L1 score 50-89% was analyzed. Results: A total of 1320 patients treated with ICI monotherapy were identified, 873 in 1L and 447 in 2L. Median follow-up was 9.6 months in 2L patients and 13.3 months in 1L patients. Patients receiving 2L ICI therapy with PD-L1 score ≥ 90% (N = 208) had longer PFS and OS compared to patients with PD-L1 score 50-89% (N = 239), with mPFS 7.1 vs. 4.2 months (HR = 0.66 [95% CI: 0.52-0.83]) and mOS NR vs. 15.8 months (HR = 0.66 [95% CI: 0.49-0.89]). 1L ICI therapy analysis revealed similar trends, as patients with PD-L1 score ≥ 90% (N = 405) had longer PFS and OS compared to patients with a PD-L1 score 50-89% (N = 468), with mPFS 8.3 vs. 5.4 months (HR = 0.78 [95% CI: 0.66-0.92]) and mOS 22.9 vs. 16.4 months (HR = 0.74 [95% CI: 0.61-0.90]). Conclusions: This analysis showed the potential of an enhanced clinical benefit in patients with aNSCLC and PD-L1 score ≥90% across ICI monotherapies in both the 1L and 2L treatment setting. These data will be further analyzed in real world populations.

FDA’s Oncology Center for Excellence Pilots Project Orbis: A framework for concurrent submission and review of oncology products among international partners

e14125

Background: Cancer therapeutics often receive FDA approval months to years before regulatory submission to other countries. [i] Registrational trials in oncology are increasingly international, with many patients enrolled outside of the United States. Harmonizing access to new global standards of treatment may facilitate optimal design and conduct of global clinical trials. Methods: In May 2019, the Oncology Center for Excellence launched Project Orbis in collaboration with the Australian Therapeutic Good Administration (TGA) and Health Canada. The aim of this initiative is to provide a framework for concurrent submission and review of oncology products among international partners to facilitate global access. Results: The first Project Orbis was a collaborative review of a supplemental application for lenvatinib and pembrolizumab for patients with advanced endometrial cancer. This review also deployed other OCE regulatory review tools including the Real-Time Oncology Review (RTOR) pilot program, which can streamline the submission of data prior to the completion and submission of the entire application, and its accompanying Assessment Aid, to facilitate discussions among regulatory agencies. Lenvatinib and pembrolizumab was approved on September 17, 2019, in conjunction with the TGA and Health Canada, three months prior to the FDA goal date. FDA, TGA, and Health Canada issued a second action under Project Orbis on November 21, 2019, with the approval of acalabrutinib for patients with chronic lymphocytic leukemia or small lymphocytic lymphoma. Several other products are under international review as part of this pilot program and a summary of timelines and outcomes will be described. Conclusions: Project Orbis is an innovative OCE initiative that leverages the Center’s longstanding communication and collaboration with international regulators. This pilot program facilitates concurrent submission and review of oncology products among global regulatory health agencies. Continued efforts under Project Orbis will build on the initial success to incorporate additional global partners including Swissmedic and Singapore’s Health Science Authority. [i] The Centre for Innovation in Regulatory Science (CIRS). R&D Briefing 70 New drug approvals in six major authorities 2009-2018: Focus on Facilitated Regulatory Pathways and Orphan Status

Metastasis free survival in older men with nonmetastatic castration-resistant prostate cancer treated with androgen receptor inhibitors: An FDA-pooled analysis

12038

Background: The FDA has approved three androgen receptor (AR) inhibitors for nonmetastatic castration-resistant prostate cancer (nmCRPC) based on improvements in metastasis-free survival (MFS). MFS is an earlier endpoint, defined as the time from randomization to either imaging-detectable distant disease or death. This pooled analysis examines MFS, time to initiation of cytotoxic chemotherapy (TTCyto), and safety outcomes in men over 80 treated with AR inhibitors. Methods: Data was pooled from three randomized controlled studies (n=4117) of AR inhibitors for nmCRPC. The treatment effect of AR inhibitors on MFS and TTCyto across age groups was evaluated using Kaplan-Meier estimates and a Cox proportional hazards regression model. Hazard Ratios for MFS and TTCyto were adjusted for baseline ECOG, total Gleason score, PSA doubling time, and prior bone-targeting therapy. Results: For patients age 80 years or older (n=675) who were treated with AR inhibitors, the hazard ratio was 0.38 (95% CI 0.29, 0.49) with an estimated median MFS of 40 months (95% CI 36, 41) versus 22 months (95% CI 18, 29) for those treated with placebo (n=348). For patients <80 (n=2019) treated with AR inhibitors, the HR was 0.31 (95% CI 0.27, 0.36) with an estimated median MFS of 41 months (95% CI 36, NR) versus 16 months (95% CI 15, 18) for those treated with placebo (n=1075). Patients over 80 also derived similar improvements in time to initiation of cytotoxic chemotherapy (HR 0.43 95% CI 0.23, 0.82), compared to their younger counterparts (HR 0.41 95% CI 0.33, 0.50). See Table for selected safety outcomes. Conclusions: In an exploratory subgroup analysis, older men (≥80) with nmCRPC derived similar benefit in MFS and time to initiation of cytotoxic chemotherapy with AR inhibitors compared with younger patients. Men age 80 and above experienced higher rates of Grade 3-4 adverse events, serious adverse events, falls, and fractures. This trend towards increased toxicity was observed regardless of treatment arm. Analysis of patient reported outcomes is ongoing. [Table: see text]

Impact of radiotherapy on risk of adverse events in patients receiving immunotherapy: A U.S. Food and Drug Administration pooled analysis

3018

Background: Immune checkpoint inhibitors (ICIs) are widely used in the treatment of multiple advanced malignancies. Radiotherapy (RT) has been used in combination with ICIs to activate tumor-specific T cell responses, and RT also promotes non-specific acute and chronic inflammatory responses both locally and systemically. More than 50% of patients receive RT at some point during their course of cancer therapy, and relatively little information is available pertaining to the impact of RT, if any, on the risk of adverse events (AEs) in patients receiving ICIs. Methods: Pooled data from prospective trials of ICIs submitted to the FDA in initial or supplemental BLAs or NDAs through 12/2019 were included (N=66). Trials from applications that were withdrawn or not approved were not included. Patients were subdivided by whether or not radiotherapy was administered at any time during the course of their cancer treatment. AEs common to both ICI treatment and RT were identified to focus on the following reactions: neutropenia, thrombocytopenia, colitis, hepatitis, pneumonitis, and myocarditis. Descriptive statistics were used to examine AEs associated with the use of radiation and ICIs. Results: A total of 25,836 patients were identified, of which 9087 (35%) received RT and 16,749 (65%) did not. Radiation was associated with similar rates of AEs overall with numerically higher hematologic toxicities and pneumonitis and numerically lower colitis, hepatitis and myocarditis (Table). Patients receiving RT were more likely to experience Grade 3-5 hematologic toxicities compared to those not receiving RT. Conclusions: To our knowledge, this is the largest report of AE risk associated with the use of radiation and ICIs. Our results show that the incidence of hematologic toxicity and pneumonitis in patients receiving RT may be slightly higher. Analysis to determine comparability of baseline demographic characteristics, comprehensive AE profile, and timing of RT is underway. [Table: see text]

FDA analysis: Impact of BMI on efficacy outcomes in multiple myeloma trials

8543

Background: Obesity has been implicated as a risk factor for the development of certain types of cancers, including multiple myeloma. Previous studies in other tumor types suggest that overweight subjects may have better outcomes, however, in relapsed/refractory multiple myeloma (RRMM), it is unknown whether body weight affects outcomes to therapy. Methods: We conducted a retrospective analysis of 13 RRMM clinical trials submitted to the FDA between 2012-2018. Patients were divided into four groups, underweight (BMI < 18.5 kg/m2), normal weight (BMI 18.5- < 25 kg/m2), overweight (BMI 25.0- < 30 kg/m2) and obese (BMI > 30.0 kg/m2). A multivariate analysis for progression free survival (PFS) and overall survival (OS), stratified by study and adjusted for age, cytogenetic risk group (Standard, High, Unknown), immunoglobin subtype (IgG Y/N), ECOG status (0-1, > 1, UNK), sex (M/F) was used to estimate the HR. Results: A total of 5898 patients were included in this analysis. The median age was 65 years (range 30-91 years). A total of 87(1.5%) patients were underweight, 1853 (31%) were normal weight, 2212 (38%) were overweight, 1332 (23%) were obese, and 414 (7%) had missing BMI. The results of the multivariate analysis of PFS and OS are shown in the Table. Conclusions: Exploratory analysis of patients with RRMM found that patients who were overweight and obese had a trend towards slightly improved PFS and OS when compared to normal weight patients. Similar trends were observed in the analyses of overall response rate and BMI (not presented in the abstract). These results are consistent with previous studies in other malignancies. Limitations include the lack of adjustment for multiple testing, the small sample of patients in the underweight category, and heterogeneity in the treatment regimens and PFS assessments in the clinical trials included in the analysis. Future studies are needed to evaluate safety and impact of treatment regimens on efficacy outcome measures based on body weight. [Table: see text]

Impact of timing of antibiotic use on clinical outcomes in patients with urothelial cancer treated with immune checkpoint inhibitors (ICIs)

5045

Background: Although recent evidence has suggested that patients who receive antibiotics (ABX) during the course of ICI treatment might decrease overall survival (OS) (1), our previous analysis did not support a difference in OS in urothelial cancer patients who did and did not use ABX during the course of ICI treatment without regard to timing (2). This updated analysis aims to addresses the question of timing; specifically, use of ABX in the 30-day window pre- or post- initiation of ICI treatment. Methods: We pooled data from 7 trials that led to drug approval and which included 1747 patients with advanced urothelial cancer treated with an ICI. Five trials enrolled patients who received prior platinum and 2 enrolled cisplatin-ineligible patients. Concomitant medication datasets were searched for systemic ABX use. The association between ABX use and survival was evaluated using Kaplan-Meier estimates and Cox proportional hazards regression models stratified by study. Results: Overall, 56% of patients were exposed to antibiotics (ABX+) and 43% were not exposed (ABX-). In an exploratory analysis, median OS was similar between arms: 9.7 vs. 9.3 months in ABX+ vs. ABX- patients, respectively (HR 0.96). However, OS results differed in the 27% of patients who were exposed to antibiotics in the 30-day window pre- or post- initiation of ICI treatment, for whom median OS was 4.7 months vs. 11.5 months in the ABX+ vs. ABX- patients, respectively (HR 1.8). This remained true after controlling for baseline risk prognostic factors (Bajorin and Bellmunt scores). Similar trends were observed for progression-free survival (PFS). Conclusions: Patients treated with ABX while on therapy with an ICI for urothelial cancer had similar OS outcomes to those not treated with ABX. However, in an exploratory analysis looking at ABX use in the 30-day window pre- or post-initiation of ICI treatment, OS appeared decreased in ABX+ vs ABX- patients. Our exploratory analyses appear to show an association of OS/PFS with timing of antibiotics. References: 1) Routy B, Science (2017) 2) Weinstock C, ASCO 2019, abstract. [Table: see text]

Impact of antibiotic use on clinical outcomes in patients with urothelial cancer receiving a programmed death protein 1 or programmed death ligand 1 (anti-PD-1/L1) antibody

4557

Background: Previous data has suggested that patients treated with anti-PD-1/L1 antibodies who receive antibiotics during their therapy might have dramatically decreased progression-free and overall survival 1,2. This has clinical implications for management of patients with suspected bacterial infection while on treatment with these agents. We assessed the relationship between antibiotic use and tumor response rate, progression-free survival, and overall survival in a large dataset of patients with urothelial cancer treated with anti-PD-1/L1 antibodies. Methods: We examined seven trials that led to drug approval and which included 1747 patients with metastatic or locally advanced urothelial cancer treated with an anti-PD-1/L1 antibody. Five trials enrolled patients who had received prior platinum-based therapy and two enrolled patients who were cisplatin-ineligible. Six were single arm trials and one was a randomized controlled trial whose control arm is not included in these analyses. Concomitant medication datasets were searched for systemic antibiotic used by each patient while on treatment. Results: Overall, 51% of patients (n=892) were exposed to antibiotics (ABX+) and 49% (n=855) were not exposed (ABX-). In these exploratory analyses, small numeric differences in OS, PFS, and ORR were seen in ABX+ vs. ABX- patients. Median OS was 9.23 vs. 9.86 months, median PFS was 105 vs 101 days, and ORR was 20% vs. 21% in ABX+ vs. ABX- patients, respectively. Conclusions: Patients who were treated with antibiotics while on therapy with an anti-PD-1/L1 antibody for urothelial cancer had similar outcomes to those who were not treated with antibiotics. Numeric differences in outcomes were not significant and did not duplicate previous analysis demonstrating a median OS that was doubled in ABX- patients1. Our exploratory analyses do not appear to demonstrate a clear need for practitioners to avoid antibiotic use in patients treated with PD-1/L1 agents for fear of significantly impacting clinical outcomes. References: 1) Tinsley et. al., ASCO annual meeting 2018, abstract 3010 2) Routy et. al., Science 05 Jan 2018: Vol. 359, Issue 6371. [Table: see text]

An FDA analysis of the association between adverse events and outcome in patients with urothelial cancer receiving a programmed death protein 1 or programmed death ligand 1 (anti-PD-1/L1) antibody

4549

Background: To assess the relationship between tumor response rate, overall survival, and the development of related adverse events of special interest (AESIs) or related immune-mediated adverse events (imAEs) in patients with urothelial cancer treated with anti-PD-1/L1 antibodies. Methods: We examined seven trials that led to drug approval and which included 1747 patients with metastatic or locally advanced urothelial cancer treated with an anti-PD-1/L1 antibody. Five trials enrolled patients who had received prior platinum-based therapy and two enrolled patients who were cisplatin-ineligible. The datasets were searched for AESIs, related AESIs, imAEs, and related imAEs. The relationship to study drug was determined by the Investigator. Immune-mediated adverse events were defined as AESIs treated with topical or systemic corticosteroids. Results: In these exploratory analyses, a related AESI was reported in 64% of responding patients and in 34% of patients who did not respond to the anti-PD-1/L1 antibody while a related imAE occurred in 28% and 12% of patients who did and did not respond to study drug, respectively. In a responder analysis, an increase in overall survival was seen in patients with related AESIs compared to those with no related AESI [hazard ratio (HR) 0.42; 95% CI: 0.37, 0.49]. Fifty-seven percent of responding patients with a related AESI reported a related AESI prior to documentation of response. Conclusions: Patients who responded to treatment with an anti-PD-1/L1 antibody were more likely to report a related AESI or related imAE. This relationship did not appear to be due to the increased duration of exposure in responding patients. Systemic corticosteroid use did not appear to affect the duration of response.

Clinical efficacy of abiraterone and enzalutamide metastatic castration sensitive prostate cancer patients who progressed rapidly on docetaxel with a genomic analysis

e16536

Background: Docetaxel has become a standard of care for mCSPC. Enzalutamide and abiraterone have been proven to improve survival in metastatic castration-resistant prostate cancer (mCRPC) patients. Little is known about patients who have been treated with docetaxel for mCSPC and subsequent therapeutic responses. This retrospective analysis is to evaluate the response duration of abiraterone and enzalutamide in patients who previously received docetaxel for mCSPC but developed mCRPC within 12 months. Methods: Clinical Trial NCT02649855 enrolled patients with newly diagnosed mCSPC who were treated with standard androgen deprivation therapy (ADT) and docetaxel (75 mg/m2 every 3 weeks for 6 cycles) sequenced with immunotherapy (PROSTVAC) from February 2016 to present. Patients who had progression (based on consecutive PSA rises or imaging) within 1 year of completing docetaxel and went on to subsequent abiraterone/enzalutamide were evaluated. (Note these are different PSA progression criteria than used in CHAARTED, Sweeney, NEJM, 2015). A PCR-based NGS panel (OncoMine Comprehensive Assay v3) will evaluate available tissue from these patients. Results: Of the 46 patients evaluated regardless of immunotherapy sequence, 15 (33%) went on subsequent therapy after progression on docetaxel for mCSPC, with 12 patients starting abiraterone/enzalutamide (7 with high volume disease and 5 with low volume disease). The median age was 62 (41-83) years. 6/12 patients (50%) initiated enzalutamide and 6/12 patients (50%) initiated abiraterone. The median duration of treatment for both was 7.43 (1.53 – 16.0) months, the median time to prostate-specific antigen (PSA) progression was 2 (0 – 11) months; the median duration of PSA decline was 2 months in patients with both high and low volume disease. Of note, 3/12 (25%) of patients did not have PSA response, all of them had high volume disease. Conclusions: These data from a small cohort suggest that patients who have progression within 12 months of completing docetaxel for mCSPC have limited subsequent benefit from enzalutamide or abiraterone. Additional studies are required to determine optimal timing and treatment sequence for patients with mCSPC who rapidly develop mCRPC. Clinical trial information: NCT02649855.

FDA analysis of depth of response (DpR) and survival across 10 randomized controlled trials in patients with previously untreated unresectable or metastatic melanoma (UMM) by therapy type

9508

Background: Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 may not capture the full spectrum of benefit that patients with melanoma derive from targeted kinase inhibitors (TKI) or immunotherapies. We explored the relationship between DpR and overall survival (OS) in patients treated with TKI (BRAF, MEK inhibitors), immunotherapy (antibodies targeting PD-1 or CTLA-4), or chemotherapy (dacarbazine or paclitaxel). Methods: Ten randomized controlled trials of patients with previously untreated UMM were pooled and evaluated by type of therapy. DpR was grouped by maximal tumor shrinkage (G0 = no shrinkage or increase, G1 = ≤25%, G2 = 26-50%, G3 = 51-75%, G4 = 76- < 100%, and G5 = 100%). We performed an exploratory analysis evaluating the association between DpR and OS using hazard ratios (HR) generated from a Cox proportional hazards model where maximal tumor shrinkage category was included as a time varying covariate. Results: There were 3778 patients evaluable for tumor response. The table displays the HR for OS by DpR group and therapy type. Estimated OS at 24m in patients with deep response ( > 75%; G4+G5) treated with TKI and immunotherapy was 69% and 92%, respectively, although many patients were censored. Conclusions: For patients with previously untreated UMM a larger DpR correlates with a longer OS, regardless of therapy type. Deep response ( > 75%) is associated with a high rate of estimated OS at 24 months in patients treated with immunotherapy. Analysis of DpR provides additional granularity of response data and may provide a more nuanced prediction of clinical outcome. [Table: see text]

Analysis of early mortality in randomized clinical trials evaluating anti-PD-1/PD-L1 antibodies: A systematic analysis by the United States Food and Drug Administration (FDA)

2516

Background: Many studies exhibit what seems to be dis-proportionately higher early mortality (EM) in anti-PD-1/PD-L1 containing arms (IO) when compared to active control arms (AC), resulting in early crossing of the Kaplan-Meier overall survival curves. We examine if EM with the use of IO is specific to certain demographic and disease characteristics. Methods: Data from 16 randomized AC trials submitted to FDA containing 6055 IO and 3604 AC patients in HNSCC, Melanoma, NSCLC, RCC, and Urothelial Carcinoma were evaluated for signs of EM. Study-specific and pooled piecewise hazard ratios (HRs) were used to quantify EM from 0 to 60 and > 60 days. Additionally, HRs up to 60 days were used to assess the extent specific subgroups account for EM. Results: Piecewise HRs comparing OS between IO and AC changed direction, > 1 to < 1 in 11 trials; melanoma (5/6), NSCLC (3/7), HNSCC (1/1), RCC (1/1), and urothelial cancer (1/1). When pooled, NSCLC studies retained this EM pattern, although attenuated, with HR (95% CI) of 1.12 (0.91, 1.38) ≤60 days and 0.66 (0.61, 0.72) after 60 days. This was not observed in the pooled melanoma studies: 0.88 (0.63, 1.24) ≤ 60 days and 0.59 (0.53, 0.67) after 60 days. EM in both arms was associated with poor ECOG performance status (PS), increased LDH, and high tumor burden. Comparing EM patients in the IO and AC arms, a larger proportion were female in the melanoma trials (41% vs. 28%), a smaller proportion had squamous histology in the NSCLC trials (32% vs. 41%), and a larger proportion were PD-L1 negative (56% vs. 36% melanoma; 60% vs. 43% NSCLC). Analysis of the pooled melanoma studies suggests PD-L1 negative melanoma patients with high baseline tumor burden and PS played a role in EM with HR before 60 days of 1.49 (0.75, 2.97). However, these results were not reproducible in NSCLC. Conclusions: Potential risk factors for EM were assessed in individual and pooled trials. While several factors—negative PD-1/PD-L1 status and high ECOG, LDH and tumor burden—seem to play a role in EM, these high-risk subgroups do not fully explain the EM patterns observed in the IO treated patients.

A phase I and randomized phase II study of cabozantinib plus docetaxel and prednisone (C+DP) versus docetaxel and prednisone (DP) alone in metastatic castrate-resistant prostate cancer (mCRPC)

173

Background: A phase I study of Cabozantinib (C) in combination with docetaxel (D) and prednisone (P) in patients (pts) with mCRPC determined that 40 mg daily was the maximum tolerated dose of C in combination with D and P (C+DP). We report a pooled analysis of the phase I and randomized phase II study comparing C+DP to DP alone. Methods: Eligible pts had mCRPC without prior chemotherapy in the castrate setting. All pts received a fixed dose of D (75 mg/m2IV day one of each 21 day cycle) and P (5 mg PO twice daily), and in the C+DP group, C at three escalating dose levels: 20 mg, 40 mg, or 60 mg in the phase I cohort (all PO daily) and 40 mg daily in the phase II cohort. Results: A total of 32 pts received C+DP (19 pts in phase I and 13 pts in the phase II cohort). 12 pts received DP alone. Baseline characteristics for C+DP vs DP included median age 69 (45 – 84) vs 69 (50-83) and median PSA 74.8 ng/ml (0.01-4093.7) vs 309.5 ng/ml (94.6 – 2649) respectively. Clinical trial information: NCT01683994. 18/32 C+DP pts had previous enzalutamide or abiraterone, with a median PFS of 13.6 months (95% CI: 5.2 – 21.0). 23/32 pts (72%) treated with C+DP required dose reduction or discontinuation of C, and 10/32 (31%) required C discontinuation. 2/32 patients (6%) in the C+DP group died on protocol, possibly related to study drug (sudden death NOS/venous thromboembolism). Grade 4 adverse events (AEs) in the C+DP group included: neutropenia (28%), leukopenia (6%), pulmonary embolism (3%), and mucositis (3%) and in DP: hyperglycemia (8%). Grade 3 AEs (>10%) in C+DP included: neutropenia (31%), febrile neutropenia (16%), leukopenia (13%), hypophosphatemia (13%) and in DP: anemia (17%). Conclusions: In pts with mCRPC, C+DP is associated with a greater PFS and PSA responses compared to DP alone. Toxicities with the combination were manageable. Further study is required to better define the potential benefits of C+DP in mCRPC.[Table: see text]

Age-related differences in patient-reported outcomes in patients with advanced lung cancer receiving anti-PD-1/PD-L1 therapy

BACKGROUND

Older adults with lung cancer often have comorbidities that may increase risk of symptomatic adverse events (AEs) and physical function decline. The objective of this study was to examine age-related differences in patient-reported symptoms and functional domains in patients with advanced lung cancer receiving immunotherapy drugs.

METHODS

Three randomized controlled trials of anti-programmed death receptor-1/programmed death-ligand 1 therapy in patients with advanced non-small cell lung cancer that included patient-reported outcomes (PROs) were identified. Baseline PRO data were pooled for treatment arms from 2 trials that included the same PRO tools. Age-related differences in baseline mean scores for each of the health-related quality of life functional and symptom scales were assessed for patients ≥70 years and <70 years. Mean change from Baseline at 3 months was also calculated and plotted for each age group. The adequacy of PRO assessments was assessed by comparing clinician-reported AE data in the 3 trials to the item content of the PRO tools included.

RESULTS

Across the 3 trials, 75 of patients were under 70 and 26% patients were 70 and older. Comparing baseline scores in the 2 trials with the same PRO tool, older adults reported small differences including lower physical functioning, less pain, insomnia and financial difficulties, and higher social functioning than younger patients at baseline. No large differences in the distributions of mean change from baseline in function or symptom were identified. Several common clinician-reported symptomatic AEs were not assessed by the PRO strategy employed in the 3 trials. Three clinician-reported symptomatic AEs (rash, fever, and pruritus) that were commonly reported in the safety data (9%-19%) were not assessed using the PRO tools employed.

CONCLUSION

While several small differences were seen, there did not appear to be large differences at baseline or in the distributions of change from baseline in PRO functional domains between younger and older patients with lung cancer undergoing anti-programmed death receptor -1/programmed death-ligand 1 therapy. Relevant symptomatic side effects were not assessed by PRO measures in these trials, and this is a limitation of current PRO assessment strategies.

Immunotherapy for biochemically recurrent prostate cancer

215

Background: Annually about 30-50,000 men are diagnosed with biochemically recurrent prostate cancer (BCRpc), defined by a rising PSA after radical prostatectomy (RP) or definitive radiation therapy (RT) with negative conventional imaging (CT and bone scan). Standard treatments include salvage therapies, androgen deprivation or surveillance. The role of immunotherapy in BCRpc is undefined. Methods: This study evaluates PROSTVAC, a pox-viral based therapeutic cancer vaccine targeting PSA, in BCRpc. Key eligibility criteria include PSA > 0.8 after RP or > 2.0 after RT with a maximum PSA of 30, PSA doubling time (DT): 5-15 months; testosterone > 100, negative CT and bone scan. Patients (pts) are randomized to vaccine for 6 months or 6 months surveillance followed by 6 months of vaccine. In a post hoc analysis delayed PSA declines were characterized as a confirmed PSA decline after an intra-study apex PSA (ISAP) defined by a peak PSA affirmed by a contiguous PSA within 10% (to exclude lab variations). 80 pts will be enrolled at NCI, Dana-Farber Cancer Institute and Memorial Sloan Kettering Cancer Center. Results: Of the 26 pts enrolled thus far, 22 have been followed for > 9 months after vaccine and are evaluable. On-study median values were age 66.8 years (54-78), PSA 2.67 ng/ml (0.83-28.5), PSA DT 7.5 months (5.1-14.9). 8 pts (38%) had delayed PSA declines after ISAP (-12% to -99%). Of 13 pts on surveillance for 6 months, only one pt had a similar decline lasting only 56 days. Conclusions: Preliminary data from this study suggests that PROSTVAC may be associated with delayed, but sustained PSA declines in BCRpc which are rarely seen in surveillance alone. Additional data will be acquired from this study, but this provides rationale to develop immunotherapy combinations in BCRpc. Clinical trial information: NCT02649439. [Table: see text]

Patient-reported outcomes in PD-1/PD-L1 inhibitor registration trials: FDA analysis of data submitted and future directions

134

Background: Patient-reported outcome measures (PROs) can capture the patient’s experience with disease and treatment. Anti-PD-1/PD-L1 therapies have unique symptomatic side effects; PRO data can help to better understand the patient experience on therapy. Health-related quality of life (HRQL) components most impacted by therapy include disease symptoms, symptomatic toxicity and physical function. Methods: We reviewed FDA registration trials for 5 immunotherapy agents (anti-PD-1/PD-L1) to evaluate trial design and PRO assessment. We assessed whether the PRO strategy assessed physical function and symptomatic immune-related adverse events (irAEs) by reviewing whether trials used a well-defined physical function domain and 8 symptoms related to irAEs reported in product labels (fatigue, diarrhea, cough, shortness of breath, musculoskeletal pain, rash, pruritis and fever). Results: Data from 25 trials across 7 disease types and 1 tumor agnostic indication were evaluated. Of these, 13 were randomized and 22 were open label. Eighteen of 25 contained PRO assessments and all 18 used > 1 instrument. The most common instruments were the EQ-5D (N = 17), followed by EORTC QLQ-C30 (N = 15). Disease-specific PRO tools were included in 8 trials (5 lung, 1 head and neck, 1 melanoma and 1 renal cell), consisting of modules or scales from EORTC (N = 5), FACIT (N = 2) or the Lung Cancer Symptom Scale (N = 1). Sixty percent of the trials (15/25) used an instrument that contained a well-defined physical function (PF) domain. No trial used a PRO strategy assessing all 8 selected symptoms related to irAEs. Conclusions: Collection of PRO data in anti-PD-1/PD-L1 trials submitted to FDA was variable, and did not consistently assess treatment related symptoms and physical function. Use of a HRQL tool with well-defined functional scales supplemented by item banks or libraries to incorporate symptoms associated with irAEs may improve understanding of the patient experience while receiving anti-PD-1/PD-L1 treatment. These data, along with other important clinical data such as hospitalizations, ER visits and supportive care medications can inform the benefit risk assessment for regulatory purposes.

A phase II study of the anti-programmed death ligand-1 antibody durvalumab (D; MEDI4736) in combination with PARP inhibitor, olaparib (O), in metastatic castration-resistant prostate cancer (mCRPC)

162

Background: Recent data suggests 25-30% of sporadic mCRPC has defects in DNA repair pathways which may confer sensitivity to PARP inhibition. Immune checkpoint blockade is a promising avenue in mCRPC treatment. We hypothesize that increased DNA damage by O will complement anti-tumor activity of immune checkpoint inhibitor, D, in mCRPC (NCT02484404). Methods: Eligible pts have mCRPC with adequate end organ function and biopsiable disease (bone or soft tissue). Prior treatment with enzalutamide and/or abiraterone is required. D is administered at 1500 mg iv q28 days with O at 300 mg po q12 h. Primary endpoint is PFS. Secondary endpoints include PSA responses, safety and ORR. Single arm pilot study with a total accrual of 25 pts. On-study core biopsies undergo mutational analysis. Results: 6 pts have enrolled (median age 67 yr [range 60-79], median ECOG PS 1 [1-2]). Median baseline PSA: 258.1 (54.1-809.9 ng/mL). 4 pts have Gleason score (GS) > 8 and 2 pts have GS of 7. Grade 3/4 adverse events include anemia 2/6 (33%), thrombocytopenia, lymphopenia, nausea, febrile neutropenia, aspiration pneumonia [1 each, (17%)]. Conclusions: Exploiting synergy of D+O is a treatment option for heavily pre-treated pts. Preliminary data shows D+O is tolerable and active in mCRPC pts without germline BRCA mutation. Paired tumor biopsies and blood samples including ctDNA are being collected. Accrual is ongoing. Clinical trial information: NCT02484404. [Table: see text]

Clinical and immunologic impact of short course enzalutamide without androgen deprivation therapy for biochemically recurrent prostate cancer

214

Background: Enzalutamide (enz) is FDA approved for advanced prostate cancer, but studies are evaluating enz in earlier stages of disease. We have conducted a clinical trial (NCT01875250) of enz ± a therapeutic vaccine in biochemically recurrent prostate cancer. Methods: Eligible patients (pts) had a PSA between 2.0-20.0 ng/ml, no metastatic disease and normal testosterone (T). Treatment for all pts included enz 160 mg daily for 84 days (D), but no T lowering therapy was permitted. This analysis evaluated all pts for the impact of enz on PSA and T regardless of randomization. Pts treated with Enz alone were evaluated for immune responses.The impact of the vaccine will be evaluated after protocol-defined requisite follow-up. Results: Median age for all pts (n = 34) was 66 years (range: 52-87), with a median on-study baseline PSA of 4.55 ng/ml (2.02-19.43). Common adverse events included fatigue and breast tenderness, but no pts discontinued enz for toxicity. The median PSA decline was 99% (range: 52% to > 99%) with 11/34 pts having undetectable nadirs. Median time to first PSA rise after 84 D course of enz was 29 D (13-70) and median recovery to baseline PSA in 25 evaluable pts was 190 D (84-469). T increased above normal limits in 18/34 pts (median Tmax = 802 ng/dl). Immune analysis (n = 12) indicated enz alone increased naïve T-cells and NK cells, and decreased several subsets of myeloid derived suppressor cells with a highly suppressive phenotype. Conclusions: The preliminary findings from this study suggest that short-course enz is well tolerated, leads to prolonged PSA suppression and enhanced immune responses in patients with biochemically recurrent prostate cancer. These immune studies provide the rationale for the use of enz in combination with immunotherapeutics in this and other malignancies. Clinical trial information: NCT01875250.

An analysis of sodium 18f-fluoride PET/CT and prostate specific antigen (PSA) changes in men with metastatic castration resistant prostate cancer (mCRPC)

203

Background: Recently there has been growing evidence that 18F-Fluoride PET/CT has increased sensitivity relative to technetium-99m diphosphonate (Tc-99m MDP) bone scan for evaluating metastatic bone disease. This analysis studied changes in 18F-Fluoride PET/CT and evaluated associations with PSA changes for mCRPC patients (pts) on enzalutamide (enz). Methods: As part of a randomized phase II study evaluating enz with or without vaccine therapy, men with mCRPC electively underwent 18F-Fluoride PET/CT at 3 month (mos) intervals [NCT01867333]. At these points serum PSA was collected. Data was taken on max SUV and volume of presumed cancerous lesions and a variable, ΣSUV*Volume, was calculated which was defined as the sum of the products of SUV max and volume of cancerous lesions. Results: At the time of our analysis, 19 pts had PSA and PET/CT data for at least 2 time points within 1 year of initiating therapy. The median baseline PSA was 19.6 ng/ml (0.76-587). All pts had predominantly bone disease with 10 having small volume lymphadenopathy. Only 1/19 pts progressed by PSA Working Group criteria. An analysis found that 18/19 pts (95%) had an association between changes in PSA and ΣSUV*Volume. Of these 18 pts, 13 had a major ( > 50%) and 1 had a minor ( > 30%) PSA response and all 14 had an accompanying decrease in ΣSUV*Volume. For 11/14 pts with PSA responses, the change in ΣSUV*Volume paralleled the change in PSA at all time points, while for 3 pts an associated change between ΣSUV*Volume and PSA was delayed by 3 mos. 4/14 pts had short term responses lasting only 3 mos followed by PSA increases. For these 4 pts the changes in ΣSUV*Volume paralleled PSA changes, decreasing at 3 mos and increasing thereafter. Finally 4/18 patients had no PSA response to therapy. All 4 pts had increases in ΣSUV*Volume which paralleled rising PSA values. Conclusions: Preliminary data from a small cohort suggests that findings on 18F-Fluoride PET/CT are associated with PSA changes. This represents a substantial difference from standard Tc-99m MDP and further suggests that 18F-Fluoride PET/CT may provide a more sensitive analysis of bone disease. Additional data from this and other studies are required.

Comparison of survival of African-American (AA) patients (pts) in docetaxel (D)-based combination therapies in metastatic castrate-resistant prostate cancer (mCRPC)

272

Background: AA pts experience greater prostate cancer (PC) incidence and mortality compared to Caucasian (C) pts but are underrepresented in clinical trials (CTs). Greater representation of AAs is required to explore differences in clinical benefit in advanced disease where recent data has reaffirmed the role of D. Methods: In a retrospective analysis, baseline characteristics, Gleason score (GS), ECOG PS, number of cycles (cys), maximum prostate-specific antigen (PSA) declines, radiographic responses, overall survival (OS) and progression-free survival (PFS) were captured in 2 recent D based CTs. Results: Of 136 pts, 28 (21%) self-identified as Black or AA. Median age of AA pts is 66 (50-78 yrs). Median GS is 8 (5-10). Median ECOG PS is 1 (0-2). 15 pts have bone and soft tissue disease; 13 pts have bone only disease. Median number of cys is 28.5 (1-63). Of 27 evaluable pts, 26 had PSA declines (-26 to -99%). Radiographic responses include 11 (39%) partial responses and 16 (57%) pts with stable disease. Median OS for AAs is 29.0 months (mos) (95% CI: 20.9-34.7 mos); median PFS is 21.5 mos (95% CI: 13.7-28.9 mos). Median OS for all non-AA pts is 24.8 mos (95% CI: 21.8-29.5 mos); median PFS is 16.1 mos (95% CI: 14.1-20.1 mos). The VEGF-634G > C SNP, associated with a more aggressive phenotype of PC, was evaluated in 54 pts. No evidence was found that genotype frequency varies between C and AA pts. Conclusions: In this analysis, AA pts did not have inferior OS (29 mos) or PFS (21.5 mos) outcomes compared to non-AA pts (24.8, 16.1 mos). Further analysis from larger studies is required to determine differential benefits of D for AA pts compared to non-AA pts. Clinical trial information: NCT00089609, NCT00942578.

Cabozantinib (C) plus docetaxel (D) and prednisone (P) in metastatic castrate-resistant prostate cancer (mCRPC)

235

Background: Docetaxel (D) improves overall survival in metastatic castrate-resistant prostate cancer (mCRPC), but benefits remain short-lived. Clinical data suggests patients (pts) with mCRPC treated with anti-androgen therapy like abiraterone (AA) or enzalutamide (ENZA) have decreased responses to subsequent therapy due to cross-resistance in the androgen pathway targeted by D, AA, or ENZA(van Soest et al, Eur J Cancer 49:18, 2013). Combining D with other agents, like cabozantinib (C), could target different cellular signaling pathways potentially minimizing tumor resistance. Methods: D naive pts receive 75 mg/m2 IV on day 1 of a 21 day cycle, and prednisone (P) 5 mg po q12 hours with C at 3 dose levels: 20, 40, or 60 mg po daily until maximum tolerated dose (MTD) is defined. In phase 2, pts who have progressed on AA or ENZA, enroll on a randomized 2 arm cohort comparing D plus C to D alone. Results: 20 pts have been accrued; 4 at 20 mg C, 8 at 40 mg C, and 7 at 60 mg C. On phase 2, 1 pt is randomized to D alone. Median age is 68 (44-84 yrs). Median baseline PSA is 94.7 (0.01-754.1 ng/mL). Gleason score is 9 (7-10). Median cycles is 9.5 (1-33). 8 pts have bone only disease, 12 pts have bone and soft tissue disease. Common grade 2 and grade 3 adverse events possibly related to C: hand/foot syndrome (4/16), oral mucositis (4/16), hypophosphatemia (4/16), and fatigue (3/16). The MTD of C is 40 mg daily with D. 15 pts were previously treated with AA or ENZA. In 13 patients previously treated with AA, median PFS has not been reached, with a median potential follow up of 12.4 months. Six month PFS is 77.8% and 9 month PFS is 60.5%. Conclusions: D plus P may have limited benefits after disease progression on AA as seen in 3 retrospective analyses demonstrating a median PFS survival of 4.6 months or less (Mezynski J, et al. Ann Oncol 23;11, 2012) (Aggarwal R, et al. Clin Genitourin Cancer 12;5, 2014) (Schweizer MT, et al. Eur Urol 66;4, 2014). PFS results seen in this trial compare favorably to previously published data of treatment with D after AA in mCRPC, suggesting the addition of C to D may help overcome acquired resistance. Further randomized trials will determine if C in combination with D will enhance clinical outcomes. Clinical trial information: NCT01683994.

A safety study of trebananib (AMG 386) and abiraterone in metastatic castration-resistant prostate cancer

218

Background: Trebananib is an angiopoietin1/2 antagonist peptibody. Androgens stimulate expression of VEGF via activation of hypoxia inducible factor-a (HIFa). Androgen deprivation therapy (ADT) is associated with lower HIF1a gene expression in prostate cancer tissue. Dual targeting of the androgen and angiogenic axis represents a potential synergistic anti-angiogenic therapeutic approach in metastatic castration resistant prostate cancer (mCRPC). In this preliminary safety study we hypothesize that trebananib in combination with abiraterone will have a favorable tolerability and efficacy profile. Methods: Patients with mCRPC were treated with abiraterone 1000mg daily and prednisone 5 mg twice daily. Trebananib was administered intravenously every week, in escalating doses from 15mg/kg to 30mg/kg on days 1, 8, 15, and 22 every 28-days. Results: A total of 9 patients were enrolled. Three of nine patients had prior chemotherapy. The median age was 63.8 (63-71yrs). No dose limiting toxicities were observed. The most common grade ≥ 2 toxicities included limb edema (3/9), hyperglycemia (1/9), gastrointestinal (2/9), fatigue (2/9), hypertension (1/9), confusion (1/9), weight gain (1/9) and insomnia (2/9). 5/9 of patients had an overall PSA decline of >30%. 8/9 patients were evaluable for response. Prior chemotherapy patients were on study for 1 and 3 months. No prior chemotherapy patients were treated for 1, 6, 9, 10, 10, and 17 months. Conclusions: Trebananib in combination with abiraterone is well tolerated and displayed an acceptable safety profile in patients with mCRPC. Based on this safety data a randomized phase II study randomizing chemotherapy-naïve mCRPC patients to either abiraterone/prednisone plus AMG 386 at 30mg/kg or abiraterone/prednisone is currently accruing at the NCI. Clinical trial information: NCIT01553188.

A phase I study of the multikinase inhibitor cabozantinib (C) plus docetaxel (D) and prednisone (P) in metastatic castrate-resistant prostate cancer (mCRPC)

108

Background: Cabozantinib (C) is a multikinase inhibitor of c-Met, vascular endothelial growth factor receptor two and RET. C has shown activity in metastatic castrate resistant prostate cancer (mCRPC), with resolution of bone lesions on bone scan (BS), regression of soft tissue/visceral disease (STD), reductions in circulating tumor cells and bone biomarkers. Combining docetaxel (D) with other agents, without overlapping toxicities, can target different cellular signaling pathways necessary for tumor survival. Methods: Patients (pts), with no prior D for CRPC, receive a fixed dose of D (75 mg/m2 IV day one of each 21 day cycle) and prednisone (P) (5 mg po q12 hours) with C at three escalating dose levels: 20 mg, 40 mg, or 60 mg (all po daily). Using a standard three-plus-three design, three to six pts are treated at each dose level until the maximum tolerated dose (MTD) has been defined. Results: Thirteen pts have been accrued; four on dose level one, six on dose level two, and three on dose level three. Median age 69 (45 to 84). Four pts have an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of zero and nine pts have a PS of one. Median Gleason score is nine (7 to 10). Median on-study prostate-specific antigen (PSA) is 129.2 ng/mL (0.01-508.5 ng/mL). Median cycles is six (1 to 17). Grade 1 adverse events (AEs), possibly related to C; dysgeusia (4/12), oral mucositis (4/12), increased ALT (3/12), and epistaxis (3/12). Grade 2 AEs; nausea (2/12), hand/foot syndrome (2/12), fatigue (2/12), dysgeusia (2/12), oral mucositis (2/12), hypophosphatemia (2/12), and anemia (2/12). Grade 3 AE is hypophosphatemia (2/12). Grade 4 AE is neutropenia (1/12). MTD of C is 60 mg. Of nine evaluable pts, six have bone only disease. Of these six, three pts have PSA declines of less than 30% with improvement on BS (two pts) or stable BS (one pt). The other three pts have PSA declines of greater than 30% and bone scan improvement. Three pts have STD and bone disease; one patient had a PSA decline of greater than 30% with improvement on BS and SD by CT scan. One patient had an increase in PSA of less than 30% with improvement on BS and CT. The third pt had PD by CT and an increase in PSA equal to 30%. PFS probability at six months is 90.0% and is 67.5% at eight months and beyond. Conclusions: The addition of C to D and P, has an acceptable toxicity profile. CT scan and BS improvements did not correlate with PSA declines in all pts. An expansion cohort will combine D plus P with C at the MTD (60 mg) to determine clinical benefit. Clinical trial information: NCT01683994.

The future of interleukin-2: enhancing therapeutic anticancer vaccines

PURPOSE

The purpose of our efforts is to trigger the immune destruction of established cancer. Interleukin (IL)-2 can mediate the regression of tumors in patients with melanoma and renal cell carcinoma. In animal models, the antitumor effects of IL-2 are mediated by T lymphocytes. Stimulation with specific antigen can enhance the ability of T cells to respond to IL-2 by triggering the rapid upregulation of the high-affinity IL-2 receptor. We are seeking to design recombinant and synthetic vaccines capable of preferentially priming T cells with specificity for tumor cells.

METHODS

The antitumor activity of experimental vaccines is being studied preclinically using recently developed murine models that employ the mouse homologues of human tumor-associated antigens. Once the most effective experimental vaccines are optimized in experimental animals, clinical trials can be conducted. Vaccines are being evaluated for their ability to mediate the regression of established tumors, and a variety of immunologic correlates are being measured.

RESULTS

In animal models, vaccines based on molecularly defined tumor-associated antigens expressed in viral vectors or delivered as "naked" DNA stimulate the expansion of CD4+ and CD8+ tumor-specific T lymphocytes. Coadministration of IL-2 with these vaccines dramatically enhances their ability to mediate the regression of established cancer. In the clinic, treatment of melanoma patients with peptide vaccine and IL-2 resulted in objective responses in approximately 40% of patients, a response rate more than twice that typically achieved with IL-2 alone. Paradoxically, tumor-specific CD8+ T-cell levels were not increased in these patients.

CONCLUSION

The addition of recombinant and synthetic cancer vaccines to a regimen of IL-2 can result in improved antitumor responses in both animal models and melanoma patients. Vaccine-primed, tumor-specific T cells may preferentially proliferate upon administration of IL-2. The apparent lack of increase in CD8+ T-cell numbers in this setting suggests that the vaccine-primed T cells functionally disappear after a transient period of activation. Preventing the disappearance of activated T cells upon IL-2 administration-for example, by blocking proapoptotic signals-may enhance the therapeutic effectiveness of anticancer vaccines.