Douglas Bootle

Abstract CT-01: BYL719, a next generation PI3K alpha specific inhibitor: Preliminary safety, PK, and efficacy results from the first-in-human study

Introduction: Constitutive activation of the phosphatidylinositol-3-kinase (PI3K) signaling pathway is implicated in many human cancers. Until recently, drugs that specifically inhibit the alpha isoform of PI3K that is activated by alterations in the PIK3CA gene have been missing. BYL719 is the first oral PI3K inhibitor that strongly and selectively inhibits the PI3K alpha isoform of PI3K. Its biological activity correlates with inhibition of various downstream signaling components of the PI3K/Akt pathway and it inhibits the proliferation of breast cancer cell lines harboring PIK3CA mutations. In vivo, BYL719 shows statistically significant dose-dependent anti-tumor efficacy in PIK3CA mutant xenograft models in rodents. Methods: BYL719 entered clinical investigation in 2010 exclusively in patients (pts) with advanced solid malignancies carrying an alteration in the PIK3CA gene. In the dose escalation phase, dose selection is guided by a Bayesian regression model with overdose control. As of 21-Sep-2011, a total of 25 pts with a variety of solid tumors, such as colon and breast cancer, have been enrolled and treated at once daily oral doses ranging from 30mg to 450mg. Results: The safety profile of the compound is characterized by mostly on-target toxicity, such as hyperglycemia (33% of pts), which was found more frequently at higher doses and is largely reversible with BYL719 interruption and treatment with oral anti-diabetics. Other commonly reported toxicities include nausea (38%) and decreased appetite, diarrhea, and vomiting (each 29%). 2 DLTs of hyperglycemia and nausea, both CTCAE grade 3, were observed in 2 pts out of 5 treated at 450mg/d. In humans, BYL719 has a low clearance, a half-life of 8.5 h and its exposure increases dose proportionally between 30mg/d and 450mg/d, displaying a low inter-individual variability in Cmax and AUC. Exposure levels reached at clinical doses above 270 mg/d correspond to exposures causing tumor stasis or regression in preclinical PIK3CA dependent xenograft models. First signs of clinical efficacy of BYL719 include 1 confirmed partial response in a patient with ER+ breast cancer treated at 270mg/d. In addition, preliminary data suggest that significant PET responses (PMR) and/or tumor shrinkage were achieved in 8 out of 17 evaluated pts. Three pts had prolonged stable disease (≥7 months) at doses below 270mg/d and overall 8 patients have been on the study for at least 4 months. Upon determination of the MTD for the once daily dosing regimen, ∼45 pts with PIK3CA altered solid tumors will be enrolled into a safety expansion arm. Also, the PK and MTD for twice daily administration of BYL719 will be investigated. Conclusion: The preliminary clinical data available so far suggest BYL719 to be well tolerated, and showing signs of clinical activity, with manageable side effects and a predictable PK profile. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr CT-01. doi:1538-7445.AM2012-CT-01

in vitro and in vivo characterization of Xr11576, a novel, orally active, dual inhibitor of topoisomerase I and Ii

XR11576, a novel phenazine, was developed as an inhibitor of both topoisomerase I and II. This study characterized the ability of XR11576 to inhibit both enzymes, and determined its in vitro and in vivo antitumor efficacy against a number of murine and human tumor models. XR11576 was a potent inhibitor of purified topoisomerase I and II &agr;, and exhibited similar potency for both enzymes. The compound stabilized enzyme–DNA cleavable complexes indicating that it acted as a topoisomerase poison. The DNA cleavage patterns obtained with XR11576 were different from those induced by camptothecin and etoposide, which are topoisomerase I and II poisons, respectively. XR11576 demonstrated potent cytotoxic activity against a variety of human and murine tumor cell lines (IC50=6–47 nM). Its activity profile was comparable to or better than that of many widely used anticancer drugs. Moreover, XR11576 was unaffected by multidrug resistance (MDR) mediated by overexpression of either P-glycoprotein or MDR-associated protein, or by down-regulation of topoisomerase II. The latter property supports the dual inhibitory mechanism of action of the compound. XR11576 exhibited a similar pharmacokinetic profile in mice and rats after either i.v. or p.o. administration. In vivo XR11576 showed marked efficacy against a number of tumors including sensitive (H69/P) and multidrug-resistant (H69/LX4) small cell lung cancer and the relatively refractory MC26 and HT29 colon carcinomas following i.v. and p.o. administration. The efficacy of XR11576 was at least comparable to that of TAS-103, originally proposed as a dual inhibitor of topoisomerase I and II. These results suggest that XR11576 is a promising new antitumor agent with oral and i.v. activity, and warrants further development.

Antitumor activity of XR5944, a novel and potent topoisomerase poison.

Inhibitors of topoisomerases are widely used in the treatment of cancer, including inhibitors of topoisomerase I (camptothecin analogs such as irinotecan and topotecan) and topoisomerase II (etoposide and doxorubicin). The novel bis-phenazine, XR5944, is a joint inhibitor of topoisomerase I and II as shown by the stabilization of topoisomerase-dependent cleavable complexes. XR5944 demonstrated exceptional activity against human and murine tumor cells in vitro and in vivo. In a range of cell lines XR5944 (IC50 0.04-0.4 nM) was significantly more potent than TAS-103, originally proposed as a joint topoisomerase I and II inhibitor, as well as agents specific for topoisomerase I or II (topotecan, doxorubicin and etoposide). In addition, XR5944 was unaffected by atypical drug resistance and retained significant activity in cells overexpressing P-glycoprotein or multidrug resistance-associated protein. Antitumor efficacy of XR5944 was demonstrated in human carcinoma xenograft models (H69 small cell lung cancer and HT29 colon). In the HT29 model, which is relatively unresponsive to chemotherapy, XR5944 (15 mg/kg i.v., q4d×3) induced tumor regression in the majority of animals (six of eight), whereas TAS-103, dosed at its maximum tolerated dose (45 mg/kg i.v., q7d×3), only induced a delay in tumor growth compared with control animals. In the H69 model, low doses of XR5944 (5 mg/kg i.v., qd×5/week for 2 weeks or 10-15 mg/kg i.v., q4d×3), induced complete tumor regression in the majority of animals. In contrast, topotecan (20 mg/kg i.v., q4d×3) or etoposide (30 mg/kg i.v., q5d×5) only slowed the tumor growth rate. These studies show that XR5944 is a highly active novel anticancer agent that is well tolerated at efficacious doses.

Abstract PD5-5: Phase I study of the PI3Kα inhibitor BYL719 plus fulvestrant in patients with PIK3CA-altered and wild type ER+/HER2- locally advanced or metastatic breast cancer

Background: BYL719 selectively inhibits the α-isoform of Class I PI3K. PI3Kα is encoded by PIK3CA, a frequently altered gene in human cancers. Preclinical data indicate BYL719 may be more effective in patients (pts) with PIK3CA-altered tumors; however there are data to suggest that PIK3CA-wild-type (wt) tumors may also be sensitive to BYL719. Here, we present updated data from the Phase I study of BYL719 + fulvestrant in pts with PIK3CA-altered or -wt ER+/HER2– locally advanced/metastatic breast cancer (BC) (NCT01219699). Methods: Adult women with PIK3CA-altered (mutation or amplification) ER+/HER2– BC received continuous oral BYL719 (300–400 mg/day; 28-day cycles) + fixed-dose fulvestrant (500 mg every 4 weeks, plus an additional dose 2 weeks after first dose) during dose escalation and expansion. Pts with PIK3CA-wt ER+/HER2– BC were enrolled into the dose expansion to receive BYL719 400 mg/day + fulvestrant. A Bayesian logistic regression model with overdose control guided dose escalation. Primary objective: to determine the maximum tolerated dose (MTD) and/or recommended phase II dose (RP2D) of BYL719 in combination with fulvestrant, which was declared previously as 400 mg/day. An expansion cohort at the MTD assessed safety (CTCAE v4.0), tolerability, pharmacokinetics (PK), and preliminary efficacy (RECIST v1.0). Results: As of May 2, 2014, 64 pts (PIK3CA-altered n=41; PIK3CA-wt n=16; PIK3CA status unknown/pending n=7) received BYL719 300–400 mg/day + fulvestrant. Median number of prior antineoplastic therapies: 5 (range: 1–12) for pts with PIK3CA-altered tumors and 5 (range: 4–16) for pts with PIK3CA-wt tumors. Prior fulvestrant treatment: 19 (46%) and 7 (44%) pts with PIK3CA-altered and -wt tumors, respectively. Overall, the most common (≥25%) adverse events (AEs; all grades/all doses) suspected to be study drug-related were hyperglycemia (41%), diarrhea (34%), nausea (30%), and vomiting (25%). The most common (>10%) study drug-related Grade 3/4 AEs (all doses) were maculopapular rash (14%) and hyperglycemia (13%). Preliminary antitumor activity was observed in this trial. At data cut-off, partial responses (PRs) were observed in 2 patients with PIK3CA-altered tumors evaluable for response (2/33, 6%), but no PRs were observed in the 15 evaluable patients with PIK3CA-wt tumors. Duration of exposure was >16 weeks in 24 (59%) patients with PIK3CA-altered tumors and in 5 (31%) patients with PIK3CA-wt tumors. PK and exposure of BYL719 + fulvestrant was similar to that observed with single-agent BYL719 at the same dose levels. At data cut-off, treatment was ongoing in 20 (49%) and 2 (13%) pts with PIK3CA-altered and -wt tumors, respectively. Conclusions: BYL719 + fulvestrant demonstrated a favorable safety profile in pts with PIK3CA-altered and -wt ER+/HER2– BC, with mostly on-target effects (i.e. hyperglycemia, rash). Preliminary clinical activity was seen in pts with PIK3CA-altered and -wt tumors, but confirmed PRs were only observed in pts with PIK3CA-altered tumors. The low number of pts with PIK3CA-wt tumors limits further conclusion. Citation Format: Filip Janku, Dejan Juric, Javier Cortes, Hope Rugo, Howard A Burris, Martin Schuler, Barbara Deschler-Baier, Mark R Middleton, Marta Gil-Martin, Jordan Berlin, Eric Winer, Douglas Bootle, Lars Blumenstein, David Demanse, Christina Coughlin, Cornelia Quadt, Jose Baselga. Phase I study of the PI3Kα inhibitor BYL719 plus fulvestrant in patients with PIK3CA-altered and wild type ER+/HER2- locally advanced or metastatic breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr PD5-5.

Phosphatidylinositol 3-Kinase α–Selective Inhibition With Alpelisib (BYL719) in PIK3CA-Altered Solid Tumors: Results From the First-in-Human Study

Purpose We report the first-in-human phase Ia study to our knowledge ( ClinicalTrials.gov identifier: NCT01219699) identifying the maximum tolerated dose and assessing safety and preliminary efficacy of single-agent alpelisib (BYL719), an oral phosphatidylinositol 3-kinase α (PI3Kα)-selective inhibitor. Patients and Methods In the dose-escalation phase, patients with PIK3CA-altered advanced solid tumors received once-daily or twice-daily oral alpelisib on a continuous schedule. In the dose-expansion phase, patients with PIK3CA-altered solid tumors and PIK3CA-wild-type, estrogen receptor-positive/human epidermal growth factor receptor 2-negative breast cancer received alpelisib 400 mg once daily. Results One hundred thirty-four patients received treatment. Alpelisib maximum tolerated doses were established as 400 mg once daily and 150 mg twice daily. Nine patients (13.2%) in the dose-escalation phase had dose-limiting toxicities of hyperglycemia (n = 6), nausea (n = 2), and both hyperglycemia and hypophosphatemia (n = 1). Frequent all-grade, treatment-related adverse events included hyperglycemia (51.5%), nausea (50.0%), decreased appetite (41.8%), diarrhea (40.3%), and vomiting (31.3%). Alpelisib was rapidly absorbed; half-life was 7.6 hours at 400 mg once daily with minimal accumulation. Objective tumor responses were observed at doses ≥ 270 mg once daily; overall response rate was 6.0% (n = 8; one patient with endometrial cancer had a complete response, and seven patients with cervical, breast, endometrial, colon, and rectal cancers had partial responses). Stable disease was achieved in 70 (52.2%) patients and was maintained > 24 weeks in 13 (9.7%) patients; disease control rate (complete and partial responses and stable disease) was 58.2%. In patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative breast cancer, median progression-free survival was 5.5 months. Frequently mutated genes (≥ 10% tumors) included TP53 (51.3%), APC (23.7%), KRAS (22.4%), ARID1A (13.2%), and FBXW7 (10.5%). Conclusion Alpelisib demonstrated a tolerable safety profile and encouraging preliminary activity in patients with PIK3CA-altered solid tumors, supporting the rationale for selective PI3Kα inhibition in combination with other agents for the treatment of PIK3CA-mutant tumors.

Population pharmacokinetics and pharmacodynamics of BYL719, a phosphoinositide 3‐kinase antagonist, in adult patients with advanced solid malignancies

AIMS The aim was to characterize the population pharmacokinetics of BYL719 in cancer patients and assess the time course of tumour response in relation to drug exposure and dosing schedule. METHODS Plasma samples and longitudinal tumour size measurements were collected from 60 patients with advanced solid malignancies who received oral BYL719 once daily (30-450 mg) or twice daily at 120 mg or 200 mg. Non-linear mixed effect modelling was employed to develop the population pharmacokinetic and pharmacodynamic model. RESULTS The pharmacokinetics were best described by a one compartment disposition model and transit compartments accounting for the lag time in absorption. The typical population oral clearance and volume of distribution estimates with their between-subject variability (BSV) were 10 l h(-1) (BSV 26%) and 108 l (BSV 28%), respectively. The estimated optimal number of transit compartments was 8.1, with a mean transit time to the absorption compartment of 1.28 h (BSV 32%). The between-occasion variability in the rate and extent of absorption was 46% and 26%, respectively. Tumour growth was modelled using a turnover model characterized by a zero order growth rate of 0.581 cm week(1) and a first order death rate of 0.0123 week(-1) . BYL719 inhibited tumour growth with an IC50 of 100 ng ml(-1) (BSV 154%). Model-based predictions showed potential for additional anti-tumour activity of twice daily dosing at total daily dose below 400 mg, but a loss of efficacy if administered less frequently than once daily. CONCLUSIONS The proposed model provides a valuable approach for planning future clinical studies and for designing optimized dosing regimens with BYL719.

Abstract P2-16-14: Preliminary safety, pharmacokinetics and anti-tumor activity of BYL719, an alpha-specific PI3K inhibitor in combination with fulvestrant: Results from a phase I study

Background: Phosphatidylinositol-3-kinase (PI3K) pathway activation has been associated with resistance to anti-estrogen receptor (ER) therapy and PIK3CA mutated ER+ breast cancer (BC) cells are sensitive to inhibition of PI3K under estrogen deprivation. In an in vitro study, the combination of BYL719 and fulvestrant was synergistic in PIK3CA mutated BC cell lines. In the BYL719 single agent part of this study out of 21 ER+ BC patients (pts), 3 partial responses were observed and 5 pts remained on the study with stable disease for over 26 weeks. Median PFS in pts with ER+ PIK3CA mutated BC was 5.5 months (Gonzalez-Angulo, 2013). Methods: This phase I study was amended to determine the Maximum Tolerated Dose (MTD) of BYL719 in combination with the ER antagonist fulvestrant in PIK3CA mutated ER+ breast cancer pts. Dose escalation of BYL719 in combination with fixed dose fulvestrant used an adaptive Bayesian logistic regression model with overdose control. The starting dose of BYL719 was 300 mg once daily, 25% below the MTD of single agent BYL719. All pts received the standard dose of 500 mg fulvestrant every 4 weeks. No dose escalation of fulvestrant was permitted. Following the MTD declaration, a dose expansion cohort will open. Results: At the data cut-off (27 March 2013), 4 pts were enrolled in the initial cohort of 300 mg/q.d. BYL719 plus 500 mg/qmonth (with an additional dose at week 2) fulvestrant, followed by 8 pts into the subsequent 400 mg/q.d. BYL719 plus fulvestrant dose combination. No pts experienced dose limiting toxicity (DLT) in the 300 mg cohort, and 1 pt experienced a DLT of CTCAE grade 3 diarrhea, vomiting, fatigue, anorexia and bloating in the 400 mg cohort. The MTD of BYL719 in combination with fulvestrant has been declared as 400 mg/q.d. The most frequent BYL719 related toxicities (>15% pts), regardless of grade and treatment group, are diarrhea (42%), hyperglycemia (33%), decreased appetite (25%), nausea (25%), and fatigue (17%). Systemic drug exposure of oral BYL719 when given in combination with fulvestrant was found to be similar to the single agent data. The patients were typically pre-treated with numerous chemotherapy, hormonal or targeted therapies. One pt in the 300 mg/q.d. cohort had a confirmed partial response, and 2 pts in the 400 mg/q.d. cohort had a partial response (one confirmed and one only occurring after the data cut-off). From the 12 breast cancer pts treated, 2 (17%) discontinued treatment due to progressive disease, and the median exposure of all pts at the time of data cut-off was 9 weeks. Conclusions: This combination displays a favorable safety and PK profile, both comparable to the single agent BYL719 experience. BYL719 in combination with fulvestrant shows encouraging preliminary anti-tumor activity, which supports further investigation of this combination. Recruitment within the dose expansion is continuing to obtain a sample size of 20 patients carrying the PIK3CA mutation. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-16-14.

Abstract LB-65: Towards defining the genetic framework for clinical response to treatment with BYL719, a PI3Kalpha-specific inhibitor.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Defining predictive biomarkers and deriving appropriate patient populations for treatment are key areas of interest in the clinical development of phosphatidyl-inositol-3-kinase (PI3K) inhibitors, but currently most clinical trials do not pre-select patients using defined genetic markers. Pre-clinical studies indicated previously that in vitro sensitivity to BYL719, a potent and selective small molecule inhibitor of the α-isoform of PI3K, was increased in cell lines derived from a subset of indications, such as HER2-positive or luminal breast cancer. Moreover, BYL719 sensitivity in vitro was positively correlated with PIK3CA mutation or amplification and HER2 amplification. PTEN or BRAF mutation, on the other hand, was associated with BYL719 insensitivity. Consequently, presence of an activating PIK3CA alteration in the tumor was a pre-requisite for patients to enroll into the BYL719 first-in-human (FIM) clinical trial. In this study, we applied massive parallel sequencing to tumor specimens from patients enrolled in the BYL719 FIM trial to comprehensively assess the genetic determinants of clinical sensitivity to BYL719. Paraffin-embedded formalin-fixed archival or pre-treatment tumor specimens were obtained from 44 patients with advanced solid tumors upon enrolment into the clinical trial. DNA was isolated and then assayed by massive parallel sequencing covering either a panel of 182 cancer-related genes at Foundation Medicine or the whole exome at the Broad Institute. Mutations were identified by focusing on genes with alterations in the COSMIC data base and excluding germline variants and were subsequently correlated with clinical benefit as defined by stable disease ≥ 4 months, tumor shrinkage ≥ 20% or objective tumor response to BYL719 using a two-tailed Fishers exact test. Focusing on a panel of 51 genes with known relevance to PI3K signaling, we observed that all pre-treatment tumor samples harbored at least one genetic abnormality and that each of the genes was altered in one or several tumor samples. TP53 (59%), APC (25%), KRAS (23%) and PTEN (18%) were the most frequently altered in addition to PIK3CA. Alterations in TP53 and KRAS were identified as statistically significant negative predictors of BYL719 sensitivity (p < 0.05), while mutations in the APC and PTEN genes were associated with a trend towards lack of benefit from treatment with BYL719. Our results suggest that definition of the genetic biomarkers that govern sensitivity to treatment with BYL719 and–most likely–other PI3Kα inhibitors in the clinic is possible upon analysis of patients tumors by massive parallel sequencing. We also demonstrate that it is feasible to routinely obtain this information in the clinical trial setting. This implies that exploration of the genetic determinants driving sensitivity or primary resistance to targeted agents in general can now be undertaken clinically. Citation Format: Jordi Rodon, Dejan Juric, Ana-Maria Gonzalez-Angulo, Johanna Bendell, Jordan Berlin, Douglas Bootle, Kathlene Gravelin, Alan Huang, Adnan Derti, Joseph Lehar, Jens Wurthner, Markus Boehm, Eliezer van Allen, Nikhil Wagle, Levi A. Garraway, Roman Yelensky, Philip J. Stephens, Vincent A. Miller, Robert Schlegel, Cornelia Quadt, Jose Baselga. Towards defining the genetic framework for clinical response to treatment with BYL719, a PI3Kalpha-specific inhibitor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-65. doi:10.1158/1538-7445.AM2013-LB-65