A phase IB dose-escalation study of the safety and pharmacokinetics of pictilisib in combination with either paclitaxel and carboplatin (with or without bevacizumab) or pemetrexed and cisplatin (with or without bevacizumab) in patients with advanced nonesmall cell lung cancer

Abstract Aim: The phosphatidylinositol 3-kinase (PI3K) pathway is a potential therapeutic target in nonesmall cell lung cancer (NSCLC). This study aimed to evaluate the pan-PI3K inhibitor pictilisib in combination with first-line treatment regimens that were the standard of care at the time of study, in patients with NSCLC.Patients and methods: A 3 3 dose-escalation study was performed using a starting daily dose of 60 mg pictilisib on days 1e14 of a 21-day cycle. Depending on bevacizumab eligibility and NSCLC histology, patients also received either paclitaxel þ carboplatin or pemetrexed þ cisplatin, bevacizumab every 3 weeks. The primary objectives of the study were to assess safety and tolerability and to identify dose-limiting toxicities (DLTs), the maximum tolerated dose (MTD) and a recommended phase II dose (RP2D), for each combi- nation. Results: All 66 treated patients experienced at least one adverse event (AE). Grade ≥III AEs, serious AEs and deaths occurred in 57 (86.4%), 56 (84.8%) and 9 (13.6%) patients, respectively.Three patients reported DLTs across the four arms of the study. The MTD was not reached in any arm and the RP2D of pictilisib was determined to be 330 mg (capsules) or 340 mg (tablets) on a ‘14 days on, 7 days off’ schedule. The best confirmed response was partial response in 29 (43.9%) patients and stable disease in 20 (30.9%) patients.Conclusion: Combining pictilisib with various standard-of-care first-line treatment regimens is feasible from a safety perspective in patients with NSCLC, and encouraging preliminary anti- tumour activity was observed.

As the most common cancer and the leading cause of cancer-related deaths worldwide, lung cancer accounted for 13.0% (1.82 million) of all new cancer cases and 19.4% (1.59 million) of cancer mortality in 2012 [1]. The majority of patients with lung cancer (85%) are diag- nosed with nonesmall cell lung cancer (NSCLC) [2]. Platinum-containing chemotherapy is the standard of care for first-line treatment of patients with advanced NSCLC [3e5]. For patients with non-squamous NSCLC and no recent history of haemoptysis, chemo- therapy may be administered in combination with bev- acizumab [3e5]. Recently, the first programmed cell death-1 immune checkpoint inhibitor, pembrolizumab, was approved by the Food and Drug Administration for first-line treatment of patients with metastatic squamous and non-squamous NSCLC, whose tumours have high programmed death-ligand 1 expression and no epidermal growth factor receptor (EGFR) or anaplastic lymphoma kinase genomic aberrations [6]. However, most patients with NSCLC eventually progress despite treatment, and 5-year survival remains poor, particu- larly for patients with stage IV disease (4.9%) [7]. Therefore, there is a significant unmet need for alter- native effective treatments for these patients.Genetic alterations in the phosphatidylinositol 3- kinase (PI3K) pathway are frequently observed in NSCLC [8], making PI3K a potential therapeutic target. These occur through mutation or amplification of the PIK3CA gene encoding the p110a catalytic subunit, loss of function of PTEN (through deletion, mutation or reduced expression), alterations in INPP4B and PHLPP phosphatases, mutations of PI3K regula- tory subunits encoded by PIK3R1 and PIK3R3 or through activation of upstream receptor tyrosine ki- nases or crosstalk with the RAS pathway [8]. Pictilisib (GDC-0941) is a potent class I pan-PI3K inhibitor, with comparable activity against mutant and wild-type forms of the p110a subunit of class IA [9]. Pictilisib has demonstrated anti-tumour activity in xenograft models of human cancers [10] and has synergistic cytotoxicity in combination with platinum-based chemotherapies, EGFR inhibitors and mitogen-activated protein extra-
cellular signal-regulated kinase inhibitors in NSCLC cell lines [11]. The single-agent maximum tolerated dose (MTD) for pictilisib from phase IA studies is 330 mg (capsule; equivalent to a 340-mg tablet) administered orally once daily, with maculopapular rash as a dose- limiting toxicity (DLT) [12].This phase IB study was designed to evaluate the safety and pharmacokinetics (PK) of pictilisib in com- bination with first-line platinum-containing treatment regimens that were the standard of care at the time of study, in patients with NSCLC.

2.Patients and methods
Eligible patients were 18 years with advanced NSCLC (stage IIIB ineligible for chemoradiotherapy, stage IV or recurrent), who were chemotherapy-na¨ıve or had received one line of chemotherapy, with an Eastern Cooperative Oncology Group (ECOG) performance score of 0 or 1 and baseline diffusing capacity of the lungs for carbon monoxide (DLCO) 50% of predicted, corrected for haemoglobin and alveolar volume. Adequate haematological and end organ function and evaluable or measurable disease (Response Evaluation Criteria in Solid Tumors [RECIST], version 1.0) were also the inclusion criteria. Patients with known central nervous system (CNS) metastases were eligible if they had evaluable/measurable disease outside the CNS. Any radiotherapy for CNS metastases must have been completed at least 8 weeks before screening and any neurosurgical resection or brain biopsy must have been performed more than 3 months before day 1.Key exclusion criteria were type 1 or type 2 diabetes (glycosylated haemoglobin 7%, fasting glucose 7.49 mmol/L and/or requiring regular medi- cation), any adjuvant or neoadjuvant anti-cancer regimen for NSCLC within 4 weeks or >1 previous anti-cancer regimen for advanced NSCLC. Additional key exclusion criteria for patients in the bevacizumab arms included inadequately controlled hypertension, prior history of hypertensive crisis or encephalopathy,myocardial infarction or unstable angina, stroke or transient ischaemic attacks, vascular disease and hae- moptysis. Patients with squamous cell NSCLC were not eligible for bevacizumab and pemetrexed combinations.This was a non-randomised, open-label, multicentre, phase IB dose-escalation study to assess the safety, tolerability and PK of pictilisib administered with paclitaxel and carboplatin with or without bevacizumab in patients with NSCLC or pemetrexed and cisplatin with and without bevacizumab in patients with non- squamous NSCLC (Fig. 1).Paclitaxel (200 mg/m2), carboplatin (6 mg/mL$min), pemetrexed (500 mg/m2), cisplatin (75 mg/m2) and bev- acizumab (15 mg/kg) were administered intravenously every 3 weeks.

Pictilisib was administered orally once daily on days 1e14 of each 21-day cycle. Patients received paclitaxel þ carboplatin bevacizumab or pemetrexed cisplatin bevacizumab on day 1 of each 21-day cycle for up to six cycles, except for cycle 1. During cycle 1, pictilisib was administered as a single agent on day 1 of a 22-day cycle followed by chemo- therapy on day 2. Patients could continue with pictilisib maintenance therapy (squamous NSCLC) or pictilisib and pemetrexed (non-squamous NSCLC), with or without bevacizumab, beyond six cycles if they had no disease progression or intolerable toxicity.A dose-escalation stage using a 3 3 design was performed for each arm to determine the MTD. A starting dose of 60-mg pictilisib on a ‘14 day in phase IA studies on a continuous once-daily schedule (330-mg capsule) [12], was used in cohort 1. Pictilisib was administered by capsule or tablet according to avail- ability. Due to the slightly higher bioavailability of the capsule (Roche/Genentech data on file) the 340-mg tablet is equivalent to the 330-mg capsule. Cohort 4 received a dose of 250 mg (capsule) or 260 mg (tablet), while cohort 5 and the expansion cohort received 330 mg (capsule) or 340 mg (tablet).The MTD of the combination was defined as the highest dose at which fewer than two of six evaluable patients had a DLT during cycle 1. DLTs were defined as study drugerelated toxicities occurring during the 22- day assessment window in cycle 1 and included: grade III non-haematological, non-hepatic organ toxicity (excluding nausea, vomiting or diarrhoea that resolved to grade I within 3 days, hypertension for patients treated with bevacizumab or hyperglycaemia within 3 days of steroid premedication for paclitaxel or peme-trexed); grade IV thrombocytopenia lasting >7 days or associated with clinically significant bleeding; grade IV neutropenia lasting >7 days; grade IV febrile neutropenia; grade III total bilirubin or hepatic transaminases (alanine aminotransferase or aspartateaminotransferase) (for patients with grade I hepatictransaminase at baseline as a result of metastases, he- patic transaminase >7.5 × the upper limit of normal was considered a DLT) and grade II DLCO with a decrease of 20% from baseline.

Patients not evaluable for DLTs were replaced, including those who withdrew from treatment before completing the first cycle for reasons other than a DLT, who missed 4 days of pictilisib treatment for reasons other than a DLT or whodid not receive the full dose of their chemotherapy regimen for reasons other than a DLT.Following identification of the MTD of pictilisib plus the various chemotherapy combinations, a cohort- expansion stage with a planned additional six to nine patients was performed for three arms to evaluate the safety, tolerability, PK and anti-tumour activity of pic- tilisib with different combination chemotherapies. The pictilisib carboplatin paclitaxel arm (Fig. 1, Arm A) was not included in the expansion part.The study was conducted in accordance with the guidelines for Good Clinical Practice. Institutional Re- view Board/Ethics Committee approval was obtained for the protocol, patient recruitment material, informed consent forms, any information given to the patient and relevant supporting information.

The study was regis- tered on ClinicalTrials.gov (NCT00974584) and the European Clinical Trials Database (EudraCT; number 2009-010780-16).The primary objectives for the study were the evaluation of safety and tolerability, the identification of DLTs and estimation of the MTD and the identification of a rec- ommended phase II dose (RP2D) for pictilisib admin- istered with the different first-line treatment regimens for advanced NSCLC. Secondary objectives included evaluation of the PK and anti-tumour activity of picti- lisib in combination with chemotherapy.Adverse events (AEs) were graded according to the National Cancer Institute – Common Terminology Criteria for Adverse Events, version 3.0 [13]. Tumour assessments were performed at baseline and at the end of cycles 2, 4, 6 and 9, then every third cycle thereafter or as clinically indicated, and disease status was categorised per RECIST, version 1.0. Blood samples were taken for pictilisib PK evaluations during cycle 1 before and after dosing on day 1, before dosing on day 9 and at study completion. Additional samples were taken on days 2 and 3 for PK evaluations of all study drugs. Plasma concentrations of pictilisib, bevacizumab and chemo- therapy drugs (including paclitaxel and its cytochromeP450 2C8 [CYP2C8]eformed metabolite, 6 a-hydrox- ypaclitaxel [6a-OH-paclitaxel]) were determined using validated liquid chromatography tandem mass spectrometry methods and PK parameters were esti- mated using non-compartmental analysis (WinNonlin 6.4; Pharsight, Mountain View, CA).Descriptive statistics were used for the safety population before study discontinuation. Summaries are presented by study arm and dose level. Data cut-off was 20th May 2015.

A total of 50 patients were treated across all arms in the dose-escalation stage, with an additional 16 patients across three arms in the cohort-expansion stage. The first patient was enrolled on 15th October 2009 and the last patient on 28th January 2014. The median age of all treated patients was 59 years (range: 34e80 years) and 53% were male (Table 1). The majority of patients (65.2%) had an ECOG performance status of 1, and 63.6% had received no prior systemic therapy (Table 1). The number of patients included in each cohort is shown in Fig. 2.The median duration of pictilisib exposure across all arms was 126 days (range 14e959 days) and the median number of pictilisib treatments administered was 79.5 (range 8e618).All patients experienced at least one AE (Table 2), most commonly nausea (68.2%), vomiting, fatigue and decreased appetite (54.5% each) and diarrhoea (48.5%) (Table 3). Grade III AEs occurred in 57 (86.4%) pa- tients (Table 2). The most common grade III AEs were neutropenia (27.3%), dyspnoea (15.2%) and anaemia and dehydration (12.1% each) (Table 4). Serious AEs were reported in 56 (84.8%) patients (Table 2), the most common of which were dehydration (10.6%), lung infection and febrile neutropenia (7.6% each), dyspnoea (6.1%) and increased blood creatinine (6.0%). There were nine deaths (13.6%) on the study (Table 2), seven from disease progression and one each from cardio- respiratory arrest and cardiac failure (cohorts 5a and 5d, respectively). No deaths were considered related to study treatment.Pictilisib treatment was discontinued in 22 (33.3%) patients due to AEs (Table 2), most commonly due to fatigue (n Z 4 p), nausea (n Z 2) and myalgia (n Z 2).

All patients had withdrawn from the study at the time of data cut-off. Withdrawal was attributed to disease progression in 32 (48.5%) patients, patient or physician decision in 18 (27.2%) patients, AEs in 11 (16.7%) patients and death (not preceded by AEs or disease progression) in five (7.6%) patients.DLTs occurred in three patients during the study. Grade III rash occurred in two patients who were treated with 330-mg pictilisib paclitaxel carboplatin bevacizumab (from cohort 5b and the cohort-expansion stage, 6b) and grade III nausea in one patient treated with 340-mg pictilisib þ pemetrexedþ cisplatin þ bevacizumab (from cohort 5c). The MTDof pictilisib in combination with paclitaxel þ carbopla- tin bevacizumab or pemetrexed þ cisplatin bevacizumab was not reached. The maximum adminis- tered dose (MAD) of 330 mg (capsules) or 340 mg (tablets) taken on a ‘14 days on, 7 days off’ schedule was selected as the RP2D of pictilisib in combination with the different regimens assessed in this study.Pictilisib is an in vitro inhibitor of CYP2C8-mediated paclitaxel 6a hydroxylation [14], and therefore could alter the CYP2C8-mediated metabolism of paclitaxel when used in the clinical setting. However, the exposure ratio of 6a-OH-paclitaxel to paclitaxel observed in pa- tients across all pictilisib dose levels was stable over time (Fig. 3) and consistent with published data for paclitaxel alone [15], suggesting that the PK of paclitaxel is inde- pendent of the administered pictilisib dose. Similarly, no differences in the PK of pictilisib, carboplatin, bev- acizumab, pemetrexed, cisplatin or paclitaxel were observed in the combination regimens compared with historical single-agent data (data not shown).

The best confirmed response at any time across the four arms of the study was partial response in 29 (43.9%) patients and stable disease in 20 (30.9%) patients. Table 5 shows the best confirmed response, time to response and duration of response by treatment arm. Time to response ranged from 39 days for patients treated with pictilisib cisplatin pemetrexed to 86 days for pa- tients treated with pictilisib carboplatin paclitaxel bevacizumab (Table 5). Median duration of response ranged from 6.6 months in the pictilisib þ cisplatin þpemetrexed þ bevacizumab arm to 9.0 months in thepictilisib þ carboplatin þ paclitaxel þ bevacizumab arm Fig. 3. e Observed 6a-OH paclitaxel: paclitaxel AUC ratio by pictilisib dose. The observed ratio of the cytochrome P450 2C8 metabolite, 6a-OH paclitaxel, to parent paclitaxel after the second daily dose of pictilisib at 60 mg, 100 mg, 165 mg, 250 mg and 330 mg. Black lines represent the median ratio for each dose level; dots represent individual subject ratios. AUC0e5, area under the plasma-concentration time curve in the first 5 hours following administration.(Table 5). Median duration of response had not been reached for patients treated with pictilisib cisplatin pemetrexed at the time of the data cut-off (Table 5). Target lesion percentage change from baseline and time on study for each patient by treatment arm are shown in Fig. 4.

This phase IB study was designed to evaluate the safety and PK of pictilisib with different first-line platinum- containing chemotherapy regimens that were the standard of care at the time of the study, in patients with NSCLC. It was a part of a larger clinical devel- opment programme undertaken to evaluate pictilisib in combination with chemotherapy, hormone therapy and targeted anti-cancer therapies across several indications.The MAD and RP2D of pictilisib when adminis- tered with chemotherapy in patients with advanced NSCLC was 330 mg (capsules) or 340 mg (tablets) administered once daily on days 1e14 of a 21-day cycle. Combining pictilisib at this dose with various chemotherapy regimens, with or without biological therapy, demonstrated an acceptable safety profile, and the AEs observed in the study were consistent with those seen in other studies with pictilisib alone [12] and/ or are commonly seen with the chemotherapy regimens used.
The response rate of 44% was sufficiently encour- aging to move forward with the phase II FIGARO study (NCT01493843). However, preliminary data from FIGARO failed to show statistically significant improvements in progression-free survival (PFS) and overall survival when pictilisib was combined with carboplatin þ paclitaxel with and without regimens [18,19]. Current strategies that try to improve the therapeutic index of PI3K inhibitors include the investigation of isoform-selective inhibitors that may demonstrate greater activity than pan-PI3K inhibitors with potentially more favourable long-term safety pro- files [20e22], or to select patients with known PI3K- activating mutations.

In conclusion, pictilisib can be safely combined with different first-line chemotherapy regimens in patients with NSCLC. However, the anti-tumour activity observed in this study did not translate to improved PFS in the randomised phase II Pictilisib FIGARO study.