Pharmacotherapeutic group: Antineoplastic agents, Protein kinase inhibitors, Phosphatidylinositol-3-kinase (PI3K) inhibitors, ATC code: L01EM03
Mechanism of action
Alpelisib is an α‑specific class I phosphatidylinositol3kinase (PI3Kα) inhibitor. Gain‑of‑function mutations in the gene encoding the catalytic α‑subunit of PI3K (PIK3CA) lead to activation of PI3Kα and AKT‑signalling, cellular transformation and the generation of tumours in in vitro and in vivo models.
In breast cancer cell lines, alpelisib inhibited the phosphorylation of PI3K downstream targets including AKT, and showed activity in cell lines harbouring a PIK3CA mutation.
In vivo, alpelisib inhibited the PI3K/AKT signalling pathway and reduced tumour growth in xenograft models, including models of breast cancer.
PI3K inhibition by alpelisib treatment has been shown to induce an increase in oestrogen receptor (ER) transcription in breast cancer cells. The combination of alpelisib and fulvestrant demonstrated increased anti‑tumour activity compared to either treatment alone in xenograft models derived from ER‑positive, PIK3CA mutated breast cancer cell lines.
The PI3K/AKT signalling pathway is responsible for glucose homeostasis, and hyperglycaemia is an expected on‑target adverse reaction of PI3K inhibition.
Clinical efficacy and safety
Study CBYL719C2301 (SOLAR-1)
Piqray was evaluated in a pivotal phase III, randomised, double‑blind, placebo‑controlled study of alpelisib in combination with fulvestrant in postmenopausal women, and men, with HR+, HER2‑ advanced (locoregionally recurrent or metastatic) breast cancer whose disease had progressed or recurred on or after an aromatase‑inhibitor‑based treatment (with or without CDK4/6 inhibitor combination).
A total of 572 patients were enrolled into two cohorts, one cohort with PIK3CA mutation and one cohort without PIK3CA mutation breast cancer. Patients were randomised to receive either alpelisib 300 mg plus fulvestrant or placebo plus fulvestrant in a 1:1 ratio. Randomisation was stratified by presence of lung and/or liver metastasis and previous treatment with CDK4/6 inhibitor(s).
In the cohort with PIK3CA mutation, 169 patients with one or more PIK3CA mutations (C420R, E542K, E545A, E545D [1635G>T only], E545G, E545K, Q546E, Q546R, H1047L, H1047R or H1047Y) were randomised to receive alpelisib in combination with fulvestrant and 172 patients were randomised to receive placebo in combination with fulvestrant. In this cohort 170 (49.9%) patients had liver/lung metastases and 20 (5.9%) patients had received prior CDK4/6 inhibitor treatment.
Patients had a median age of 63 years (range: 25 to 92 years). 44.9% patients were 65 years of age or older and ≤85 years. The patients included were White (66.3%), Asian (21.7%) and Black or African American (1.2%). The study population included one male subject enrolled in the PIK3CA mutant cohort and treated with alpelisib and fulvestrant. 66.0% and 33.4% of subjects had an ECOG performance status of 0 and 1, respectively.
97.7% of patients had received prior endocrine therapy. In 67.7% of subjects, the last therapy prior to study enrollment was endocrine therapy. Letrozole and anastrozole were the most commonly used endocrine therapies. The setting of last endocrine therapy prior to study enrollment was therapeutic in 47.8% of subjects and adjuvant therapy in 51.9% of subjects. Overall, 85.6% of the patients were considered to have endocrine‑resistant disease; primary endocrine resistance (de novo resistance) was observed in 13.2% and secondary endocrine resistance (relapse/progression following an initial response) in 72.4% of patients.
In both cohorts (with or without PIK3CA mutation), demographics and baseline disease characteristics, ECOG performance status, tumour burden and prior antineoplastic therapy were well balanced between the study arms.
During the randomised treatment phase, alpelisib 300 mg or placebo was administered orally once daily on a continuous basis. Fulvestrant 500 mg was administered intramuscularly on cycle 1 days 1 and 15 and then at day 1 of a 28‑day cycle during treatment phase (administration ±3 days).
Patients were not allowed to cross over from placebo to alpelisib during the study or after disease progression.
The primary endpoint for the study was progression‑free survival (PFS) using Response Evaluation Criteria in Solid Tumors (RECIST v1.1), based on the investigator assessment in patients harbouring a PIK3CA mutation. The key secondary endpoint was overall survival (OS) for patients with a PIK3CA mutation status.
Other secondary endpoints included PFS for patients without PIK3CA mutation, OS for patients without PIK3CA mutation.
Primary efficacy analysis
At the final PFS analysis, the median duration of follow-up (between randomisation and data cut-off date of 12-June 2018) was 20 months. The results demonstrated a statistically significant improvement in PFS by investigator assessment in the PIK3CA mutant cohort for patients receiving alpelisib plus fulvestrant, compared to patients receiving placebo plus fulvestrant with an estimated 35% risk reduction of disease progression or death in favour of treatment with alpelisib plus fulvestrant.
Primary PFS results were supported by consistent results from a blinded independent review committee (BIRC) assessment in this cohort, from a randomly selected subset of 50% of randomised patients.
Table 8 Study C2301 ‑ Summary of efficacy results (cohort with PIK3CA mutation)
| | Piqray + fulvestrant (n=169) | Placebo + fulvestrant (n=172) |
| Data using primary analysis data cut‑off date of 12 June 2018 |
| Median progression free survival (PFS) (months, 95% CI) |
| Investigator radiological assessment# |
| PIK3CA mutant cohort (N=341) | 11.0 (7.5 to 14.5) | 5.7 (3.7 to7.4) |
| Hazard ratio (95% CI) | 0.65 (0.50 to 0.85) |
| p‑valuea | 0.00065 |
| Blinded independent review committee assessment*# |
| PIK3CA mutant cohort (N=173) | 11.1 (7.3 to16.8) | 3.7 (2.1 to5.6) |
| Hazard ratio (95% CI) | 0.48 (0.32 to 0.71) |
| p‑value | N/A |
| CI = confidence interval; N = number of patients; N/A = is not applicable a p‑value is obtained from the one‑sided stratified log‑rank test. # Per RECIST 1.1 * Based on 50% sample‑based audit approach |
In the cohort with PIK3CA mutation, PFS subgroup analyses per investigator assessment by randomisation stratification factors showed a generally consistent treatment effect in favour of the alpelisib arm, irrespective of presence or absence of lung/liver metastases.
In the subgroup of 170 patients with presence of lung/liver metastases, the PFS HR (95% CI) was 0.56 (0.40, 0.79); median PFS was 3.7 months (95% CI: 2.9, 6.1) in the placebo plus fulvestrant arm and 9.0 months (95% CI: 5.6, 14.5) in the alpelisib plus fulvestrant arm.
Among 20 patients with prior CDK4/6 inhibitor use the hazard ratio (HR) for PFS was 0.48 (95% CI: 0.17, 1.36); median PFS was 1.8 months (95% CI: 1.7, 3.6) in the placebo plus fulvestrant arm and 5.5 months (95% CI: 1.6, 16.8) in the alpelisib plus fulvestrant arm.
Overall response rates are summarized in Table 9.
Table 9 Overall response rate and clinical benefit rate in the PIK3CA mutant cohort per investigator assessment (Data cut-off date: 18-Jun-2018)
| Analysis | Piqray plus fulvestrant (%, 95% CI) | Placebo plus fulvestrant (%, 95% CI) | p-valuec |
| Full analysis set | N=169 | N=172 | |
| Objective Response Ratea | 26.6 (20.1 to 34.0) | 12.8 (8.2 to 18.7) | 0.0006 |
| Clinical Benefit Rateb | 61.5 (53.8to 68.9) | 45.3 (37.8 to 53.1) | 0.002 |
| Patients with measurable diseased | N=126 | N=136 | |
| Objective Response Ratea | 35.7 (27.4 to 44.7) | 16.2 (10.4 to 23.5) | 0.0002 |
| Clinical Benefit Rateb | 57.1 (48.0 to 65.9) | 44.1 (35.6 to 52.9) | 0.02 |
| a ORR= proportion of patients with confirmed Complete Response or Partial Response b CBR: proportion of patients with confirmed Complete Response or Partial Response, or (Stable Disease or Non-Complete Response/Non-Progression Disease >=24 weeks) c p-values are nominal and are obtained from the Cochran-Mantel Haenszel test. d measurable disease: the presence of at least one measurable nodal or non-nodal lesion at Baseline. |
Figure 1 Kaplan-Meier plot of progression free survival in the PIK3CA mutant cohort per investigator assessment (Data cut-off date: 18-Jun-2018)
Final overall survival analysis
The final OS analysis was conducted using a data cut-off date of 23-Apr-2020.
With a median duration from randomisation to data cut-off of approximately 42 months, a total of 87 (51.5%) deaths were reported in the alpelisib plus fulvestrant arm and 94 (54.7%) in the placebo plus fulvestrant arm, the HR was 0.86 (95% CI: 0.64, 1.15; p = 0.15, one-sided) and the pre-specified O'Brien-Fleming efficacy boundary of p ≤ 0.0161 was not crossed. Median OS was 31.4 months (95% CI: 26.8, 41.3) in the placebo plus fulvestrant arm and 39.3 months (95% CI: 34.1, 44.9) in the alpelisib plus fulvestrant arm.
Figure 2 Kaplan-Meier plot of overall survival in cohort with PIK3CA mutation (cut-off date of 23-Apr-2020)
OS subgroup analyses by randomisation stratification factors demonstrated a generally consistent treatment effect.
Cohort without PIK3CA mutation
No PFS benefit was observed in patients whose tumours did not have a PIK3CA tissue mutation.
CBYL719X2402 (BYLieve)
Alpelisib was evaluated in a Phase II, multicenter, open-label, three-cohort, non-comparative study in combination with endocrine therapy (either fulvestrant or letrozole) in adult patients (pre- and post-menopausal women and men), 18 years or older, with HR-positive, HER2-negative locally advanced or metastatic breast cancer harbouring PIK3CA mutation(s), and whose disease has progressed on or after prior treatments.
Table 10 CBYL719X2402 Patients assignment based on most recent prior therapy and treatment regimen
| | Cohort A | Cohort B | Cohort C |
| Patient inclusion, based on their most recent prior therapy | CDK4/6i plus any AI | CDK4/6i plus fulvestrant | Patients who failed prior AI based therapy and received systemic chemotherapy or endocrine therapy |
| Treatment received in Study X2402 | Alpelisib 300 mg plus fulvestrant (500 mg) | Alpelisib 300 mg plus letrozole (2.5 mg) | Alpelisib 300 mg plus fulvestrant (500 mg) |
Patients were treated until disease progression, intolerable toxicity, or until 18 months after last subject first treatment. Treatment crossover between cohorts was not permitted in this study
The primary objective of the study was to assess the proportion of patients who were alive without disease progression at 6 months based on local Investigator assessment per RECIST 1.1. Analysis of the primary endpoint was to be performed separately for each cohort.
Using a data cut-off date of 17 December 2019, data for Cohort A only are available. The primary analysis was performed for the modified Full analysis set (mFAS), defined as all subjects in Cohort A with a PIK3CA mutation confirmed by a Novartis-designated laboratory who received at least one dose of study treatment (n=121). With a median duration of follow-up of 11.7 months (calculated from the start of treatment to the date of data cut-off), 61/121 patients (50.4%, 95% CI: 41.2, 59.6) were alive without disease progression at 6 months.
Median progression-free survival (PFS), one of the secondary endpoints was 7.3 months (95% CI: 5.6, 8.3) in Cohort A, based on investigator assessment.
Figure 3 Kaplan-Meier plot of time of PFS per local Investigator assessment (Cohort A) – mFAS (cut-off date of 17-Dec-2019)
Prior use of fulvestrant in study CBYL719X2102
Patients with prior fulvestrant use were not included in the pivotal study. In the phase I study CBYL719X2101, 39 subjects reported prior fulvestrant use. The best overall responses to treatment with alpelisib plus fulvestrant for the 21 subjects with PIK3CA mutations and measurable disease at baseline were partial response in 7 subjects, stable disease in 11 subjects, and progressive disease in 2 subjects. Hence, the evidence of efficacy of this treatment in patients previously treated with fulvestrant is not established due to the limited data at this time (see section 4.4).
Paediatric population
The European Medicines Agency has waived the obligation to submit the results of studies with Piqray in all subsets of the paediatric population in breast cancer (see section 4.2 for information on paediatric use).