Factors leading to alpelisib discontinuation in patients with hormone receptor positive, human epidermal growth factor receptor-2 negative breast cancer

Phase I/Ib Trial of Inavolisib Plus Palbociclib and Endocrine Therapy for PIK3CA-Mutated, Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced or Metastatic Breast Cancer

PURPOSE

To investigate the safety, tolerability, pharmacokinetics (PK), and preliminary antitumor activity of inavolisib, a potent and selective small-molecule inhibitor of p110α that promotes the degradation of mutated p110α, in combination with palbociclib and endocrine therapy (ET), in a phase I/Ib study in patients with PIK3CA-mutated, hormone receptor-positive/human epidermal growth factor receptor 2-negative locally advanced/metastatic breast cancer (ClinicalTrials.gov identifier: NCT03006172).

METHODS

Women ≥18 years of age received inavolisib, palbociclib, and letrozole (Inavo + Palbo + Letro arm) or fulvestrant (Inavo + Palbo + Fulv arm) until unacceptable toxicity or disease progression. The primary objective was to evaluate safety or tolerability.

RESULTS

Fifty-three patients were included, 33 in the Inavo + Palbo + Letro arm and 20 in the Inavo + Palbo + Fulv arm. Median duration of inavolisib treatment was 15.7 and 20.8 months (cutoff: March 27, 2023), respectively. Treatment-related adverse events (TRAEs) occurred in all patients; the most frequent were stomatitis, hyperglycemia, and diarrhea; grade ≥3 any TRAE rates were 87.9% and 85.0%; 6.1% and 10.0% discontinued any treatment due to TRAEs in the Inavo + Palbo + Letro and Inavo + Palbo + Fulv arms, respectively. No PK drug-drug interactions (DDIs) were observed among the study treatments when administered. Confirmed objective response rates were 52.0% and 40.0% in patients with measurable disease, and median progression-free survival was 23.3 and 35.0 months in the Inavo + Palbo + Letro and Inavo + Palbo + Fulv arms, respectively. Available paired pre- and on-treatment tumor tissue and circulating tumor DNA analyses confirmed the effects of study treatment on pharmacodynamic and pathophysiologic biomarkers of response.

CONCLUSION

Inavolisib plus palbociclib and ET demonstrated a manageable safety profile, lack of DDIs, and promising preliminary antitumor activity.

Alpelisib-Induced Diabetic Ketoacidosis: A Pharmacovigilance Analysis of the FDA Adverse Event Reporting System and Review of the Literature

BACKGROUND

Alpelisib is a PI3K inhibitor indicated with fulvestrant for treatment of advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, PIK3CA-mutated breast cancer. In the phase III SOLAR-1 trial, grade 3/4 hyperglycemic events were reported in 36.6% of patients receiving alpelisib-fulvestrant compared to 0.7% receiving placebo-fulvestrant. As case reports of diabetic ketoacidosis (DKA) have been associated with alpelisib use, the goal of this study was to characterize the FAERS reported cases of this severe adverse effect.

METHODS

A retrospective disproportionality analysis was performed using the FAERS database by calculating the reporting odds ratio (ROR) of DKA events with alpelisib from 2019 to 2022. A PubMed literature review of case reports characterizing alpelisib-induced DKA was performed.

RESULTS

Pharmacovigilance database analysis revealed significance in reporting among 87 DKA cases with alpelisib (ROR 9.84, 95% confidence interval 7.3-13.2), including hospitalization and death as reported outcomes. Review of 11 published case reports reveals median onset of DKA at 14 days with successful rechallenge possible.

CONCLUSION

Significant association with reporting exists between DKA and alpelisib exposure. We observed similar median time to onset of hyperglycemia between our analysis compared to that reported in SOLAR-1. Considering early onset of this toxicity, it is imperative that patients be closely monitored when initiating alpelisib. Addition of a preemptive antihyperglycemic or escalation in those previously on antihyperglycemic medications is beneficial in decreasing the severity of hyperglycemia with alpelisib. Further study investigating risk factors is warranted to better elucidate which patients require preemptive therapy.

A New Wave of PI3Kα Inhibitors

SUMMARY

This is the first peer-reviewed report of an allosteric, mutant-selective PI3Kα inhibitor, STX-478, that reduces PIK3CA-mutant tumor growth in mice. However, in contrast to the FDA-approved PI3Kα isoform-selective inhibitor alpelisib, STX-478 does not induce hyperglycemia or other metabolic dysfunctions. See related article by Buckbinder et al., p. 2432 (7).

Jean DJ, Tieu T, Ladd B, Hilbert B, Wang W, Alltucker JT, Manimala S, Kryukov GV, Brooijmans N, Dowdell G, Jonsson P, Huff M, Guzman-Perez A, Jackson EL, Goncalves MD, Stuart DD. STX-478, a Mutant-Selective, Allosteric PI3Kα Inhibitor Spares Metabolic Dysfunction and Improves Therapeutic Response in PI3Kα-Mutant Xenografts

Phosphoinositide 3-kinase α (PIK3CA) is one of the most mutated genes across cancers, especially breast, gynecologic, and head and neck squamous cell carcinoma tumors. Mutations occur throughout the gene, but hotspot mutations in the helical and kinase domains predominate. The therapeutic benefit of isoform-selective PI3Kα inhibition was established with alpelisib, which displays equipotent activity against the wild-type and mutant enzyme. Inhibition of wild-type PI3Kα is associated with severe hyperglycemia and rash, which limits alpelisib use and suggests that selectively targeting mutant PI3Kα could reduce toxicity and improve efficacy. Here we describe STX-478, an allosteric PI3Kα inhibitor that selectively targets prevalent PI3Kα helical- and kinase-domain mutant tumors. STX-478 demonstrated robust efficacy in human tumor xenografts without causing the metabolic dysfunction observed with alpelisib. Combining STX-478 with fulvestrant and/or cyclin-dependent kinase 4/6 inhibitors was well tolerated and provided robust and durable tumor regression in ER+HER2- xenograft tumor models.

SIGNIFICANCE

These preclinical data demonstrate that the mutant-selective, allosteric PI3Kα inhibitor STX-478 provides robust efficacy while avoiding the metabolic dysfunction associated with the nonselective inhibitor alpelisib. Our results support the ongoing clinical evaluation of STX-478 in PI3Kα-mutated cancers, which is expected to expand the therapeutic window and mitigate counterregulatory insulin release. See related commentary by Kearney and Vasan, p. 2313. This article is featured in Selected Articles from This Issue, p. 2293.

Structure-based drug design, synthesis, and biological evaluation of novel 1,3,5-triazine or pyrimidine derivatives containing benzoyl hydrazine moiety as PI3Kα selective inhibitors

Phosphoinositide 3-kinase (PI3K) was an important cellular signal transducer, while PI3Kα was the most mutated family member in cancer. Selective PI3Kα inhibitors have become the frequent research in recent years because of their excellent curative effect and reduced side effects. Here, we described a series of PI3Kα inhibitors with 1,3,5-triazine or pyrimidine skeleton containing benzoyl hydrazine based on the pan-PI3K inhibitor ZSTK474 relying on the strategies of structure-based drug discovery (SBDD) and computer-aided drug design (CADD). Among them, compound F8 exhibited improved selective PI3Kα inhibition with an IC50 value of 0.14 nM and more significant anti-proliferative activities against three tumor-derived cell lines (PC-3 IC50 = 0.28 μM, HCT-116 IC50 = 0.57 μM, and U87-MG IC50 = 1.37 μM) than ZSTK-474. Compound F-8 induced a great decrease in mitochondrial membrane which caused cell cycle arrest at G1 phase and apoptosis in U87-MG cells in a dose-dependent manner. Furthermore, compound F8 induced significant tumor regressions in a xenograft mouse model of U87-MG cell line with no clear evidence of toxicity following intraperitoneal injection of 40 mg/kg. Compound F8 may serve as a PI3Kα-selective inhibitor and provided the opportunity to spare patients the side effects associated with broader inhibition of the class I PI3K family.

Real world outcomes with alpelisib in metastatic hormone receptor-positive breast cancer patients: A single institution experience

Background

It is critically important to study the real-world data of FDA-approved medications to understand the response rates and toxicities observed in the real-world population not represented in the clinical trials.

Methods

We reviewed charts of patients diagnosed with metastatic, hormone receptor-positive, human epidermal growth factor receptor 2 negative, PIK3CA-mutated breast cancer treated with alpelisib from May 2019 to January 2022. Clinical characteristics and treatment outcomes were collected. The association of clinical characteristics with responses and adverse events (AEs) was evaluated using the logistic regression model.

Results

27 patients were included. Median age at alpelisib initiation 67 years (range: 44, 77 years). Majority of patients had excellent performance status at time of alpelisib initiation. Most patients had chronic comorbidities, notably; 2 patients had controlled type 2 diabetes mellitus at time of alpelisib initiation. Majority had a median of three lines of therapy (range: 1, 7) before alpelisib. Clinical responses were determined using RECIST v1.1. 3/27 (11.11%) patients discontinued therapy before response assessment due to grade 3 AEs. Overall response rate was 12.5% (3/24), with all partial responses (PR). The median duration of response was 5.77 months (range: 5.54, 8.98). 14/27 (51.9%) of patients required dose interruption/reduction. Overall, 23/27 (85.19%) patients discontinued alpelisib of which 11 (47.83%) discontinued alpelisib due to AEs. Median duration of treatment was 2 months in patients who had grade 3 AEs (range: <1.00, 8.30) and 6.28 (1.15, 10.43) in those who did not. Any grade AEs were reported in 24/27 (88.9%) patients, namely, hyperglycemia 16/27 (59.3%), nausea 11/27 (40.7%), diarrhea 10/27 (37.0%), fatigue 7/27 (25.9%) and rash 6/27 (22.2%). Grade 3 AEs were reported in 13/27 patients (50%), namely, hyperglycemia in 7/27 (53.8%) patients followed by skin rash 4/27 (30.8%), GI side effects 3/27 (23.1%). Those with progressive disease as best response to alpelisib, had more non-metabolic comorbidities, higher number of liver metastases, PIK3CA E545K mutations, and shorter duration on therapy compared to those with PR and stable disease.

Conclusion

Patients should be counseled about the toxicity and modest benefit observed with alpelisib in real-world clinical practice when used in later lines of therapy.