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On April 17, 2020, the FDA approved tucatinib in combination with trastuzumab and capecitabine for the treatment of patients with advanced unresectable or metastatic HER2-positive breast cancer, including patients with brain metastases, who have received one or more prior anti-HER2-based regimens in the metastatic setting. This was the first new molecular entity evaluated under Project Orbis, an FDA Oncology Center of Excellence initiative, which supports concurrent review of oncology drugs by multiple global health authorities. Approval was based on the HER2CLIMB trial, which randomized patients to receive tucatinib or placebo with trastuzumab and capecitabine. Tucatinib demonstrated efficacy compared with placebo in progression-free survival [PFS; HR: 0.54; 95% confidence interval (CI): 0.42–0.71; P < 0.00001] and overall survival (OS; HR: 0.66; 95% CI, 0.50–0.87; P = 0.00480). Patients with either treated and stable or active brain metastases made up 48% of the study population. PFS in patients with brain metastases confirmed benefit (HR: 0.48; 95% CI, 0.34–0.69; P < 0.00001). The benefit in patients with brain metastases allowed for inclusion of this specific population in the indication. Important safety signals included diarrhea and hepatotoxicity which are listed under Warnings and Precautions. This article summarizes the FDA thought process and data supporting the favorable benefit–risk profile and approval of tucatinib.

Purpose: Restrictive eligibility criteria induce differences between clinical trial and “real-world” treatment populations. Restrictions based on prior therapies are common; minimizing them when appropriate may increase patient participation in clinical trials. Experimental Design: A multi-stakeholder working group developed a conceptual framework to guide evaluation of prevailing practices with respect to using prior treatment as selection criteria for clinical trials. The working group made recommendations to minimize restrictions based on prior therapies within the boundaries of scientific validity, patient centeredness, distributive justice, and beneficence. Recommendations: (i) Patients are eligible for clinical trials regardless of the number or type of prior therapies and without requiring a specific therapy prior to enrollment unless a scientific or clinically based rationale is provided as justification. (ii) Prior therapy (either limits on number and type of prior therapies or requirements for specific therapies before enrollment) could be used to determine eligibility in the following cases: a) the agents being studied target a specific mechanism or pathway that could potentially interact with a prior therapy; b) the study design requires that all patients begin protocol-specified treatment at the same point in the disease trajectory; and c) in randomized clinical studies, if the therapy in the control arm is not appropriate for the patient due to previous therapies received. (iii) Trial designers should consider conducting evaluation separately from the primary endpoint analysis for participants who have received prior therapies. Conclusions: Clinical trial sponsors and regulators should thoughtfully reexamine the use of prior therapy exposure as selection criteria to maximize clinical trial participation. See related commentary by Giantonio, p. 2369

On April 4, 2019, the FDA approved a supplemental new drug application for palbociclib (IBRANCE), to expand the approved indications in women with hormone receptor (HR)-positive, HER2-negative advanced or metastatic breast cancer (MBC) in combination with an aromatase inhibitor or fulvestrant, to include men. Palbociclib was first approved in 2015 for use in combination with letrozole for the treatment of estrogen receptor–positive, HER2-negative advanced breast cancer as initial endocrine-based therapy in postmenopausal women and subsequently in 2016 in combination with fulvestrant in women with HR-positive, HER2-negative advanced breast cancer with disease progression following endocrine therapy. The current approval was primarily based on the results of the PALOMA-2 and PALOMA-3 trials and, supported by real-world data from electronic health records and insurance claims. To support the safety evaluation in male patients, data from two phase I studies with palbociclib and safety information from the global safety database, were also reviewed. This article summarizes FDA decision-making and data supporting the approval of palbociclib for the treatment of male patients with HR-positive, HER2-negative advanced or MBC.

Background: Three cyclin dependent kinase 4/6 inhibitors (CDKIs) are approved by the Food and Drug Administration (FDA) for the treatment of patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer in combination with hormonal therapy. However, the choice of when to initiate CDKI therapy (in the first- or second-line setting, or with aromatase inhibitor or fulvestrant) can be clinically challenging as studies have not directly compared these two approaches, nor have studies determined the benefit of continuation of CDKI therapy with changes in hormonal therapy backbone. Methods: Patient-level data from eight randomized controlled pivotal trials submitted to the FDA for new or supplemental marketing applications were pooled. We performed exploratory analyses of the predictive power of the baseline patient and disease characteristic data to forecast outcomes based on a specific treatment pathway. Variables included were: age, race, ethnicity, country and continent of origin, height, weight, body mass index (BMI), menopause status, estrogen receptor (ER) status, progesterone receptor (PR) status, ECOG performance score, histological type, histological grade, and initial disease stage. Additionally, baseline levels at the time of enrollment of alanine aminotransferase (ALT), albumin, alkaline phosphatase, aspartate aminotransferase (AST), bilirubin, blood urea nitrogen (BUN), calcium, creatinine, hemoglobin, magnesium, potassium, sodium, lymphocytes, neutrophils, platelets, and white blood cells. Statistical and machine learning algorithms were used to build predictive models based on the clinical trial results. Results: The pooled studies included 4580 breast cancer patients. Baseline random survival forest models were constructed for patients that received a CDKI plus hormonal therapy and for patients that received hormonal therapy alone. Preliminary findings for these models produced prediction accuracies of 69.2% for the CDKI model and 70.6% for the hormonal therapy alone model. Median predicted survival times for patients were calculated in both treatment scenarios and used to identify those that were more likely to benefit from initial use of CDKIs and those less likely to benefit. Through further analysis of the patients in each group, we identified patient characteristics that are prognostic of survival. Conclusions: This exploratory analysis utilized clinical trial data to create a model where clinical and disease characteristics are entered to come up with an efficacy prediction. Future efforts will extend this model to predict adverse event development. Citation Format: Jeremy Mason, Yutao Gong, Laleh Amiri-Kordestani, Suparna Wedam, Jennifer J Gao, Harpreet Singh, Richard Pazdur, Peter Kuhn, Gideon Blumenthal, Julia A Beaver. Prediction of CDK inhibitor efficacy in ER+/HER2- breast cancer using machine learning algorithms [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD2-07.

On February 19, 2016, the FDA approved palbociclib (Ibrance, Pfizer) for use in combination with fulvestrant (Faslodex, AstraZeneca) for the treatment of women with hormone receptor (HR)-positive, HER2-negative advanced or metastatic breast cancer (MBC) with disease progression following endocrine therapy. The approval was based on the results of a randomized, double-blind, placebo-controlled trial conducted in 521 pre- and postmenopausal women with HR-positive, HER2-negative advanced or MBC. Patients were randomized (2:1) to receive palbociclib plus fulvestrant (n = 347) or placebo plus fulvestrant (n = 174). The primary endpoint was investigator-assessed progression-free survival (PFS). A statistically significant and clinically meaningful improvement in PFS (9.5 months vs. 4.6 months) was observed in patients receiving palbociclib plus fulvestrant [HR 0.46; 95% confidence interval (CI), 0.36–0.59; P < 0.0001]. Safety data confirmed the known adverse reaction profile of palbociclib. The most common adverse reactions (>20%) in patients treated with palbociclib were neutropenia, leukopenia, infections, fatigue, nausea, anemia, stomatitis, headache, diarrhea, and thrombocytopenia. This approval was granted in the context of a prior accelerated approval for palbociclib in combination with letrozole in patients with HR-positive, HER2-negative advanced breast cancer as initial endocrine-based therapy. Clin Cancer Res; 22(20); 4968–72. ©2016 AACR.

On September 30, 2013, the FDA granted accelerated approval to pertuzumab (Perjecta; Genentech, Inc.) for use in combination with trastuzumab and docetaxel as neoadjuvant treatment of patients with HER2-positive, locally advanced, inflammatory, or early-stage breast cancer (either greater than 2 cm in diameter or node positive) as part of a complete treatment regimen for early breast cancer. The approval was based in part on a randomized multicenter trial in the indicated population that allocated 417 patients to neoadjuvant treatment with trastuzumab–docetaxel (TD), pertuzumab–trastuzumab–docetaxel (PTD), pertuzumab–trastuzumab, or pertuzumab–docetaxel. PTD was administered preoperatively every 3 weeks for four cycles. Following surgery patients received three cycles of 5-fluorouracil, epirubicin, and cyclophosphamide every 3 weeks and trastuzumab every 3 weeks to complete 1 year of therapy. The pathologic complete response rates by the FDA-preferred definition [absence of invasive cancer in the breast and lymph nodes (ypT0/is ypN0)] were 39.3% and 21.5% in the PTD and the TD arms, respectively (P = 0.0063). The most common adverse reactions with PTD were alopecia, diarrhea, nausea, and neutropenia. This approval was based on the totality of evidence, particularly improved survival in the metastatic breast cancer trial, and a fully accrued confirmatory trial. Clin Cancer Res; 20(21); 5359–64. ©2014 AACR.

Background: With recent FDA approvals of inhibitors of Cyclin Dependent Kinases 4 and 6 (CDK 4/6) in combination with endocrine therapy for the treatment of postmenopausal women with hormone-receptor positive metastatic breast cancer (MBC), an increasing number of older adults will be treated with this class of agents. An improved understanding of the safety and efficacy of CDK 4/6 inhibitors in this population is important to inform clinical decision making for the treatment of older patients. Methods: Data from two prospective randomized controlled studies (n=1334) of different CDK 4/6 inhibitors in combination with an aromatase inhibitor for the initial treatment of postmenopausal patients with hormone-receptor positive MBC were pooled and analyzed. The effect of age on progression free survival (PFS) was explored using Kaplan Meier (KM) estimates and a Cox-proportional hazard model. Safety analysis included adverse events up to 30 days after last administration of drug based on standardized adverse event datasets. Results: Age was balanced between the two studies, and between treatment arms within each study. The median age of women was 62 (range 23-91). Of the 1334 total patients, 42% were ≥65, and 24% were ≥ 70. For patients ≥70 who were treated with a CDK4/6 inhibitor in combination with an aromatase inhibitor, the estimated PFS was not reached (95% CI: 25.1months, NR) vs an estimated 18 months (95% CI: 13.8, 31.3) for those treated only with an aromatase inhibitor. For patients Safety was evaluated in the 778 patients who received at least one dose of CDK4/6 inhibitor. Adverse Events by Age in Patients Treated with a CDK4/6 Inhibitor Patients < 65 yearsPatients≥65 yearsPatients≥70 years N=447N=331N=187 n (%)n (%)n (%)Grade 1-2 Adverse Events437 (98)324 (98)185 (99)Grade 3-4 Adverse Events340 (76)276 (83)159 (85)Serious Adverse Events72 (16)88 (27)50 (27)Adverse Events Leading to Discontinuation35 (8)56 (17)38 (20)Adverse Events leading to dose reduction and/or interruption323 (72)253 (76)147 (79)Selected Adverse Events Neutropenia (all grades)341 (76)256 (77)150 (80)Grade 3-4 neutropenia292 (65)228 (69)134 (72)Infections (all grades)190 (43)165 (50)100 (53)Hepatotoxicty (all grades)79 (18)51 (15)34 (18)Grade 3-4 hepatotoxicity32 (7)16 (5)12 (6)Fatigue (all grades)195 (44)153 (46)89 (48)Grade 3 fatigue11 (2)11 (3)7 (4) Conclusions: This exploratory analysis suggests the use of a CDK4/6 inhibitor in combination with an aromatase inhibitor for the first line treatment of HR+ MBC in older women results in similar efficacy benefit as seen in younger women. Although incidence and severity of Grade 1-4 adverse reactions appeared similar between age groups, greater serious adverse events and discontinuations occurred in patients ≥65. The inclusion of greater numbers of patients ≥70, in clinical trials will further inform clinicians about the safety and efficacy of CDK4/6 inhibitors in older adults. Citation Format: Singh H, Howie LJ, Bloomquist E, Wedam S, Amiri-Kordestani L, Tang S, Sridhara R, Ibrahim A, Goldberg K, McKee A, Beaver JA, Pazdur R. A U.S. food and drug administration pooled analysis of outcomes of older women with hormone-receptor positive metastatic breast cancer treated with a CDK4/6 inhibitor as initial endocrine based therapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS5-06.

Background: A reduction in mammographic density(MD) has been associated with the reduction in breast cancer risk among those taking tamoxifen. Aromatase inhibitors (AIs) show promise for breast cancer prevention in postmenopausal women. We are conducting a phase II trial of exemestane in women at increased risk for breast cancer. The primary endpoint for this study is change in MD. Methods: Subjects were screened and enrolled at two sites: Center for Cancer Research, National Cancer Institute and Lombardi Comprehensive Cancer Center, Georgetown University Hospital. Eligible participants are at increased risk for breast cancer by virtue of: Gail model risk ≥1. 7% over 5 years; high risk pathological lesion (e.g. lobular neoplasia, ductal carcinoma in situ); known BRCA1/2 deleterious mutation or prior stage I/II breast cancer at least 2 years from breast cancer treatment and not treated with AIs. Women were excluded if AP spine T-score was Results:For the 22 subjects included in this analysis 15 were eligible due to a high risk pathological lesion, 4 by Gail Model and 3 by prior breast cancers. 18 had film screen mammograms at baseline and 12 months, 4 had film screen mammograms at baseline and digital mammogram at 12 months. Mammographic density declined 7% (p=0.0006, 95% CI −11% to −3%) at one year. The change in MD ranged from −26% to +14% and the standard deviation was 9%. In regard to the four subjects who had film screen mammograms at baseline and digital at follow up, the baseline percent dense areas were slightly higher than average but this did not reach statistical significance (p=0.32 by the Wilcoxon rank sum test). The 12 month MD comparison was similar to the 18 subjects with film images (p=0.90). Conclusions: Exemestane use was associated with a statistically significant decrease in MD at one year. Prior evaluations of AI therapy in high risk women have not shown a significant decline in MD, however time on treatment was shorter and other third generation AIs were used. Although the number of subjects is small, MD did not differ significantly between film screen and digital mammograms. We will further evaluate change in MD in the entire cohort at 1 and 2 years and between film screen and digital mammography. Phase III trials are on-going to evaluate the effect of exemestane on breast cancer prevention. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-07-03.

Abstract #5086 Background: The aromatase inhibitors (AIs) show promise for breast cancer prevention in postmenopausal women. However these agents have been shown to decrease bone mineral density in women with breast cancer. Exemestane, a steroidal aromatase inhibitor, may be more bone sparing than the non-steroidal aromatase inhibitors. Methods: We conducted a phase II trial of exemestane in postmenopausal women at increased risk of breast cancer to assess the effect on anterior-posterior (AP) spine and total hip bone mineral density (BMD). Eligible participants are at increased risk for breast cancer by virtue of: Gail model risk > 1.7% over 5 years; high risk pathological lesion (e.g. lobular neoplasia, ductal carcinoma in situ); known BRCA1/2 deleterious mutation or prior stage I/II breast cancer at least 2 years from breast cancer treatment and not treated with AIs. Women were required to undergo DEXA scan of the AP spine and hip at baseline and were excluded if AP spine T-score was ≤-2.5. AP spine measurements were done twice at each time point and the results averaged. Study participants receive exemestane 25 mg, calcium carbonate 1200 mg and vitamin D 400 IU daily for two years. We report the results of a planned interim safety analysis assessing one year change in bone density in the first 18 subjects. Student's t-test was used to determine relative change from baseline in AP spine and total hip BMD. Results: To date, 30 women have enrolled in the trial and 21 have completed 1 year of exemestane. Three women discontinued agent after an average of 3 months due to joint pain. For the 21 included in this analysis 15 were eligible due to a high risk pathological lesion, 4 by Gail Model and 2 by prior breast cancers. The average change in AP spine BMD from baseline to 1 year (N= 21) is –1.3 %, range -10.0 to +7.0% (p=0.20 for the null hypothesis of zero overall change; 95% C.I. for the mean -3.2% to +0.7%). Average AP spine T score is -0.28 at baseline and -0.45 at one year. Change in total hip BMD is -1.4%, range -7.5% to 5.9% (p=0.058, 95% C.I. -2.8% to +0.1%). Average total hip T score is -0.05 at baseline and -0.17 at one year. Conclusions: These preliminary data suggest that exemestane 25 mg/day for one year with concurrent calcium and vitamin D has acceptable effects on bone density in postmenopausal high risk women, although there were wide ranges in effects. The observed average reduction in BMD is less than the reported effect in treatment studies of women with invasive breast cancer. Studies are in progress to determine whether exemestane use by postmenopausal women is effective in reducing the risk of invasive breast cancer. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5086.