Streicher, Howard

1043 Background: In estrogen receptor (ER) positive MBC, mutations (e.g. ESR1), identified from tumor biopsies or cfDNA, confer resistance. The concordance between mutations observed in tumor and cfDNA and the implications for response to Z-endoxifen, a potent anti-estrogen, are unknown. Methods: We previously conducted a phase I trial of Z-endoxifen in endocrine refractory, ER positive MBC. Seven dose levels were considered ranging from 20 to 160 mg/day followed by expansion cohorts (EC) of 40, 80, and 100 mg/day. Pretreatment blood samples (all pts) and fresh tumor biopsies (EC) were collected prospectively. Tumor and cfDNA were evaluated by targeted NGS. Results: 41 pts (38 evaluable) were enrolled. Prior endocrine therapy included aromatase inhibitors (37/38, 97%), fulvestrant (22/38, 58%) and tamoxifen (26/38, 68%). Substantial endoxifen exposure without DLTs at doses above 80 mg/day led to a halt in dose escalation and opening of the EC. Overall clinical benefit (stable > 6 months [7 pts.] or partial response by RECIST criteria [3 pts.]) rate was 26.3% (95%CI: 13.4-43.1%). cfDNA was obtained from 36 pts and mutations were identified in 13 (36%) including ESR1 [ Y537N or D538G] (5), PIK3CA [ H1047R or E542K] (8), TP53 [ K132R, R248Q, R267Q, or H179Y] (4), AKT ( Q79K) (1), and KRAS ( G12D) (1). In 5 pts with cf ESR1 mutations, 4 had additional cfDNA mutations including PIK3CA (3), and TP53 (1). PFS was shorter in pts with cfDNA mutations relative to those without (median: 61 vs.132 days; log-rank p = 0.021). Discordance was observed between tumor and cfDNA mutations where 3/7 PIK3CA tumor mutations were detected by cfDNA, 1/2 TP53 tumor mutations were detected by cfDNA, and 0/1 AKT tumor mutations were detected by cfDNA. Conversely, 2 pts had cfDNA mutations (either ESR1, TP53 or AKT) undetected in tumor. Conclusions: The absence of cfDNA mutations in patients with endocrine resistant, MBC treated with Z-Endoxifen was associated with significantly longer PFS. Given the discordance between tumor and cfDNA sequence data, future studies must determine which approach maximizes prognosis and prediction of benefit for estrogen-targeted therapy. Clinical trial information: NCT01327781.

Purpose Endoxifen is a tamoxifen metabolite with potent antiestrogenic activity. Patients and Methods We performed a phase I study of oral Z-endoxifen to determine its toxicities, maximum tolerated dose (MTD), pharmacokinetics, and clinical activity. Eligibility included endocrine-refractory, estrogen receptor–positive metastatic breast cancer. An accelerated titration schedule was applied until moderate or dose-limiting toxicity occurred, followed by a 3+3 design and expansion at 40, 80, and 100 mg per day. Tumor DNA from serum (circulating cell free [cf); all patients] and biopsies [160 mg/day and expansion]) was sequenced. Results Of 41 enrolled patients, 38 were evaluable for MTD determination. Prior endocrine regimens during which progression occurred included aromatase inhibitor (n = 36), fulvestrant (n = 21), and tamoxifen (n = 15). Patients received endoxifen once daily at seven dose levels (20 to 160 mg). Dose escalation ceased at 160 mg per day given lack of MTD and endoxifen concentrations > 1,900 ng/mL. Endoxifen clearance was unaffected by CYP2D6 genotype. One patient (60 mg) had cycle 1 dose-limiting toxicity (pulmonary embolus). Overall clinical benefit rate (stable > 6 months [n = 7] or partial response by RECIST criteria [n = 3]) was 26.3% (95% CI, 13.4% to 43.1%) including prior tamoxifen progression (n = 3). cfDNA mutations were observed in 13 patients ( PIK3CA [n = 8], ESR1 [n = 5], TP53 [n = 4], and AKT [n = 1]) with shorter progression-free survival ( v those without cfDNA mutations; median, 61 v 132 days; log-rank P = .046). Clinical benefit was observed in those with ESR1 amplification (tumor; 80 mg/day) and ESR1 mutation (cfDNA; 160 mg/day). Comparing tumor biopsies and cfDNA, some mutations ( PIK3CA, TP53, and AKT) were undetected by cfDNA, whereas cfDNA mutations ( ESR1, TP53, and AKT) were undetected by biopsy. Conclusion In endocrine-refractory metastatic breast cancer, Z-endoxifen provides substantial drug exposure unaffected by CYP2D6 metabolism, acceptable toxicity, and promising antitumor activity.

Abstract Background: Endemic nasopharyngeal carcinoma (NPC) refers to non-keratinizing (NK) subtypes harboring Epstein Barr virus (EBV) that frequently express programmed death-ligand 1 (PD-L1). We recently reported ≥30% of NPC harbor MHC class 1 gene alterations in a whole genome study. Method: We investigated the activity of nivolumab (NIVO) & relationship with PD-L1 & HLA expression (exp) in tumor cells (TC) & tumor infiltrating cells (TIL). Eligible patient (pt)s had to fail ≥ 1 prior line of platinum-based chemo. NIVO (3mg/kg IV, q2 weeks) was given until disease progression (PD). Archived tumors were analyzed for PD-L1 (DAKO) & HLA mutations (indicated by loss of HLA-A &/or B exp). Result: A total of 45 pts were enrolled across 11 sites from Oct 2015 to June 2016. Overall, 43 and 44 pts were evaluable respectively for response rate (RR, RECIST) & adverse events (AE). The median age was 57 years, 77% pts were males & 84% were Asians. The median number of prior chemo was 3 (range 1-9 lines). Of the 43 evaluable pts, there were 8 confirmed (19%, 95% CI: 8-33%) & 1 unconfirmed partial response (PR), 17 PD (40%), 14 stable disease (SD, 33%) & 3 pts were not assessed. One pt (MD015-027) had an unconfirmed clinical CR in an occipital metastasis (met). Pts received a median of 3 cycles of NIVO (range 1 - 14). Median overall survival has not been reached yet. Of the 44 pts evaluable for AE, 8 (18.2%) had grade 3 or higher treatment-related AEs & 1 pt died of sepsis. The most common grade 3 or higher AEs were increase in alanine/aspartate aminotransferase (n=3), & 1 pt respectively for hyponatremia, neutropenia, fatigue & diarrhea. Of the 21 tumor samples analyzed, 11/21 (52%) had >1% PD-L1 expressed mainly in TC. Table 1 outlines relationship between RR & PD-L1 exp. All pts with PR had >5% PD-L1 exp & one pt (34003-022) with CR (nasopharynx) & PR (lung mets) had the highest exp (80%). Majority of pts with PD had <1% PD-L1 exp tumors. One primary progressor (34003-032) had a PD-L1 +ve tumor harboring a complete loss of HLA-B signal (TC), but intact signal in TILs & stromal cells. Conclusion: NIVO is active in this heavily pre-treated group of pts with NK-NPC and longer follow-up is needed for survival endpoints. Preliminary result suggests PD-L1 exp may predict benefit from NIVO. The analytical result of all 45 tumors will be presented. Table 1.PD-L1 exp and RECIST response in 21 ptsPD-L1%espRR%PRSDPD0-11<1%-265%24-10%--120%-1-30%11-80%1--Total498 Citation Format: Brigette B. Ma, Boon Cher Goh, Wan T. Lim, Kwok W. Lo, Edwin P. Hui, Jonathan W. Riess, Mark Agulnik, Alex Y. Chang, Julie A. Kish, Dean W. Lim, Douglas R. Adkins, Kevin J. Cullen, Barbara J. Gitlitz, Nathan R. Foster, Adam M. Pettinger, Sanna Mckinzie, Ka F. To, Brian Costello, Howard Streicher, Anthony T. Chan. Multicenter phase II study of nivolumab in previously treated patients with recurrent and metastatic non-keratinizing nasopharyngeal carcinoma - Mayo clinic Phase 2 Consortium P2C-MN026, NCI9742, NCT02339558 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT076. doi:10.1158/1538-7445.AM2017-CT076

Abstract Background: AI's are more effective than TAM in ER+ breast cancer. In AI refractory MBC, the response rate to TAM is 0% (Osborne 2011). Z-Endx is an active metabolite of TAM and among TAM treated women in the adjuvant and metastatic settings, reduced CYP2D6 metabolism and low Endx concentrations (Css <20 nM) have been associated with increased likelihood of disease recurrence. Preclinical studies have demonstrated greater Z-Endx exposure and anti-tumor activity with oral Z-Endx compared to equivalent doses of oral TAM (Reid 2014) Methods: We conducted a phase I trial to determine the maximum-tolerated dose (MTD) and evaluate the toxicities, clinical activity, and pharmacokinetics (PK) of Z-Endx in patients (pts) with ER+, AI refractory MBC. Unlimited prior endocrine regimens were allowed. An accelerated titration schedule was applied (2 pts/dose level) until moderate toxicity or DLT, followed by a 3+3 design and then to expansion cohorts (40, 80, and 100 mg/day). Z-Endx was administered orally once daily (28 day cycle). Eye exams were performed at baseline, and end of cycles 2 and 6. PK was performed during cycle 1 and prior to subsequent cycles. For pts in the expansion cohorts, tumor biopsies were obtained at baseline for DNA sequencing (Foundation Medicine). Plasma cholesterol levels were obtained at baseline and after 1 cycle. Results: From March 2011 to Dec 2014, 41 pts (38 evaluable), median age 60, received Z-Endx once daily encompassing 7 dose levels (20-160 mg/daily). The median number of prior hormonal regimens was 2 and 3 for the dose escalation and expansion cohorts, respectively. Dose escalation was stopped at 160 mg/day given MTD not reached and attainment of mean Endx Css of 3.6 uM. Cycle 1 DLT (PE) was observed in one patient (60 mg). No eye toxicity was observed. PK demonstrated mean Endx Css of > 1 uM at all dose levels ≥ 40 mg/day. Antitumor activity was observed at multiple dose levels including 3 confirmed partial responses and an additional 7 with stable disease for ≥6 cycles. Of these 10 pts, 9 had prior progression on both AI and fulvestrant and 3 additionally on TAM. After 1 cycle, total and LDL cholesterol decreased > 20 points in 54% and 40% of pts, respectively. Tumor sequencing in the expansion cohorts (n=14) did not identify ESR1 mutations; however, ESR1 amplification was identified in 1 pt with prolonged stable disease (>200 days). Of 6 pts with rapid progression (≤2 cycles), 4/6 had either CCND1 amplification (n=1) or at least one of the following activating mutations: ERBB2 L755S (n=1), AKT1 E17K (n=1), MTOR E1799K (n=1). Conclusions: The direct administration of Z-END provides substantial drug exposure, acceptable toxicity, and "proof of principle" antitumor activity in endocrine resistant MBC. While the MTD was not determined, the goal of achieving Endx Css concentrations of > 1 uM was achieved. Tumor sequencing identified pts with predicted and confirmed endocrine resistance. A randomized phase II comparing endoxifen (80 mg/day) with TAM in AI refractory MBC was recently activated (NCT02311933). Supported in part by CA 133049, CA186686, CA15083, CA116201, and CA15083. Citation Format: Goetz MP, Suman VJ, Reid JM, Northfelt DW, Mahr MA, Dockter T, Kuffel M, Buhrow SA, Safgren SL, McGovern RM, Collins JM, Streicher H, Hawse JR, Haddad TC, Erlichman C, Ames MM, Ingle JN. Final results of a first-in-human phase I study of the tamoxifen (TAM) metabolite, Z-Endoxifen hydrochloride (Z-Endx) in women with aromatase inhibitor (AI) refractory metastatic breast cancer (MBC) (NCT01327781). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD2-03.

Abstract Background: Breast cancer recurrence has been shown to differ based upon CYP2D6 genotype and endoxifen (Endx) exposure following treatment with tamoxifen (TAM) in the adjuvant setting. The average Endx Css is 29 nM (range, 2-80 nM) in TAM treated patients at a dose of 20 mg/day. Administration of Endx itself to patients is predicted to provide adequate, consistent, active drug levels in all treated patients, resulting in clinical benefit. As part of two phase 1 trials of oral Endx to determine the safety, tolerability, and MTD, we characterized the pharmacokinetics and in vivo metabolism of Endx. Methods: Patients were given escalating daily oral doses of Endx (28 day cycle) over the dose range of 20 - 160 mg/day in Phase I trials at the Mayo Clinic and NCI. Pharmacokinetics sampling was performed on days 1, 7, 14 and 28, and prior to subsequent cycles. Endx plasma concentrations and metabolite profiles were determined by HPLC and LC/MS/MS. Results: 44 patients with ECOG PS 0-1 have been enrolled to date encompassing 8 dose levels in the Mayo (25 women with AI refractory MBC; median age 58 yrs, range 41-83 yrs) and NCI (19 women with ovary (9), breast (4), desmoid (2), fallopian tube (2), endometrial cancer (2); median age 64 yrs, range 43-75 yrs) studies. Day 1 Endx peak concentrations (Cmax) were reached 4h after the Endx oral dose and mean values of Cmax, C24h, and AUC0-24h increased in proportion to dose. Css was achieved on day 7 and 3.5-fold accumulation (t1/2= 50.5 h) was observed on day 28. At the starting dose ( 20 mg/day) and highest dose level (160 mg/day), Endx Css values of 146 ng/ml (390 nM) and 1950 ng/ml (5200 nM), respectively, were achieved and maintained throughout the 28-day treatment. Endx Css values remained unchanged following continuous dosing for 8-10 months. The mean apparent steady-state clearance was 6.2 L/h. We also characterized the Endx metabolite profile in patient plasma and urine. Metabolites detected in plasma include nor-Endx, N-hydroxy-Endx, Endx-catechol, methoxy-Endx catechol, and Endx-glucuronide, and appear in amounts much lower compared to Endx. Like the parent drug, metabolites accumulated in plasma over the 28-day cycle. Characterization of the pharmacokinetics of Nor-Endx, a putative aromatase inhibitor, is ongoing and will be presented. Conclusion: In these ongoing Phase I studies, daily administration of Endx is well tolerated with Css consistently above those obtained following administration of standard dose tamoxifen. In the Mayo study, expansion at 20 and 100 mg/day has commenced to perform translational studies and further characterize Endx PK. In the NCI study, dose escalation continues to establish the maximum tolerated dose. Supported in part by R01CA 133049, U01 CA69912, P30CA 15083, P50CA 116201 and NCI Contracts CM52206 and HHSN261201100014C. Citation Format: Joel M. Reid, Matthew P. Goetz, Shivaani Kumar, Renee M. McGovern, Sarah A. Buhrow, Stephanie L. Safgren, Vera J. Suman, Travis J. Docktor, Charles Erlichman, Howard Streicher, James H. Doroshow, Jerry Collins, Matthew M. Ames. Pharmacokinetics and in vivo metabolism of Z-endoxifen: Results from two phase I studies in women with ER+ breast cancer, gynecologic malignancies and desmoids. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4631. doi:10.1158/1538-7445.AM2014-4631

Abstract Background: In AI refractory MBC, TAM anti-tumor activity is limited (median PFS 4.5 months). In patients (pts) receiving TAM in the adjuvant and metastatic setting, breast cancer recurrence has been shown to differ based upon CYP2D6 genotype and Endx exposure. In collaboration with NCI, Z-Endx (NSC #750393) was synthesized and preclinical pharmacology studies demonstrated that oral Z- Endx resulted in > 20 fold Endx exposure compared to an equivalent dose of TAM and significantly greater anti-tumor activity than TAM in AI sensitive and resistant MCF7 xenografts. We conducted a phase I study of Z-Endx in women with ER+, AI refractory MBC to identify dose-limiting toxicities (DLT), a maximum tolerated dose (MTD) and a dose associated with steady state concentrations (Css) of ≥ 2 uM, based on the IC50 of recently identified Endx substrates: PKC and PI3K. Methods: Pts were enrolled to an accelerated titration schedule (2 pts/dose level) until moderate toxicity or DLT, and then to a 3+3 design. Z-Endx was administered orally once daily (28 day cycle). Eye exams were performed at baseline, end of cycle 2, and after 6 cycles. PK was performed on days 1-2, 3, 7, 14, and 28, and prior to subsequent cycles. Results: 23 women with AI refractory MBC (median 56 yrs, range 41-83) received Z-Endx once daily encompassing 7 dose levels (Table 1). The median number of prior chemotherapies and hormonal therapies in the metastatic setting were 2 and 2, respectively. Dose escalation continues at 160 mg/day and the MTD has yet to be determined. Cmax and AUC increased in a dose-dependent manner. A 20 and 100 mg/day dose yields Css of 0.39 and 2.48 uM, respectively. Significant anti-tumor activity was observed including 1 pt (100 mg/day) with a PR lasting 225 days; 1 pt (80 mg/day) with a 30% reduction in tumor size (PFS 169 days) and 2 pts (60 and 80 mg/day) with stable disease for >270 days. No eye toxicity was observed. Conclusions: In women with AI refractory MBC, the MTD of Z-Endx HCl has not been determined but Endx Css concentrations of > 2 uM and substantial anti-tumor activity has been observed. Following completion of the 160 mg/day dose, expansion at 20 and 100 mg/day will commence to perform translational studies and further characterize Endx pk. A randomized phase II examining two different doses of Z-Endx is planned in AI refractory MBC. Supported in part by CA 133049, CA69912, CA15083, CA116201, and CA15083. Table 1Dose Level (mg/day)Number of Treatment CyclesModerate or Severe Toxicities ReportedTumor ResponseProgression-free Survival (days)28 day Z-Endx Css (uM) 20 (n = 2)2; 3Gr 2 hot flashes (1 pt)----60; 850.39 40 (n = 2)2; 6noneStable (1 pt)61; 1670.66 60 (n = 6)1; 2; 2; 5; 8; 14Gr 4 Triglycerides (1 pt);Gr 3 thromboembolic event (1 pt); Gr 2 hot flashes, anemia, and hypoalbuminemia (1 pt)Stable (3 pts)125+; 56; 57; 132; 232; 4331.01 80 (n = 3)4; 6; 10Gr 2 hot flashesStable (3 pts)113; 169; 2961.61 100 (n = 3)1; 2; 8Gr 2 nausea (1 pt); Gr 2 irritability (1 pt)PR (1 pt)30; 56; 2252.48 120 (n = 3)1; 2; 4Gr 2 hypersomnia, paresthesia, and peripheral sensory neuropathy (1 pt)—39; 54; 1082.18 * Bold face toxicities occurred during cycle 1 Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD3-4.