Friedman, R.

3598 Background: Drug resistance to topotecan can be the result of BCRP/ABCG2 expression. BCRP is a member of the ABC transporter family that pumps anticancer drugs out of the cell. Lapatinib is a potent and selective dual inhibitor of epidermal growth factor receptor (EGFR or ErbB1) and ErbB2 (Her2/Neu). 4-aminoquinazoline tyrosine kinase inhibitors have been shown to enhance the cytotoxicity of topotecan through inhibition of BCRP-mediated drug efflux in cancer cells. Methods: Thirty-seven patients with advanced stage cancers were enrolled at escalating dose levels of lapatinib and topotecan in cohorts IA, IB and IIB (MTD). Treatment schedule included lapatinib (750 - 1500 mg/d) daily for 21 (cohort IA) or 28 days (cohort IB) and topotecan (2.4 - 4.0 mg/ m2), days 1, 8 and 15; cycles were repeated every 28 days. Three patients were treated at each dose level, 18 on cohort IA, 9 on cohort IB and 10 at MTD (cohort IIB). Assessments of toxicity were performed with each cycle and clinical response was determined per RECIST criteria every other cycle. Results: The MTD for cohorts IA and IB was reached at a dose of 1250 mg of lapatinib and 3.2 mg/m2 of IV topotecan on days 1, 8 and 15. No DLT were seen during the dose escalation stage of cohorts IA and IB. Ten patients were enrolled at the MTD. There were no grade 4+ events. Thirteen grade 3+ events, considered to be related to treatment, were seen in 6 patients. The most common grade 3+ toxicities included dehydration (2) diarrhea (2), nausea (3), vomiting (2), neutropenia (1), thrombocytopenia (1), and fatigue (1). No abnormalities in left ventricular ejection fraction were noted. Stable disease was seen in 46% of the 37 patients. Conclusions: The combination of lapatinib and topotecan is a well-tolerated regimen. The MTD for the combination is lapatinib 1,250 mg orally once daily for 21 or 28 days and topotecan 3.2 mg/m2 on days 1, 8 and 15. Pharmacokinetic analysis for drug interaction will be available for presentation at the meeting. Supported in part by GSK and Mayo Clinic No significant financial relationships to disclose.

Abstract Background: Estrogen receptor (ER)-negative tumors and human epidermal growth factor 2-Neu (HER2) positive breast cancers are known to be more clinically aggressive subtypes of breast cancer and account for 30% of all breast cancers. Women with HER2 + breast cancers, whether ER+ or ER -, require cytotoxic chemotherapy with a HER2-targeting agent, and often have adverse outcomes. Thus, preventive agents are needed to reduce the incidence of these subtypes of aggressive breast cancer. Lapatinib, a dual tyrosine kinase inhibitor, inhibits epidermal growth factor receptors (EGFR) and HER2 kinases and has shown to decrease breast cell proliferation in invasive breast cancer and adjacent premalignant lesions. Therefore, we conducted a multi-institutional randomized Phase II clinical trial to study the effects of the signal transduction inhibitor lapatinib in women with HER2-positive or EGFR-positive ductal carcinoma in situ (DCIS). Methods: Randomized participants received either lapatinib (750mg, 1000mg, or 1500mg) or placebo daily for 2-6 weeks prior to their surgery. After minimal accrual, the trial was later amended to lapatinib 1000mg or placebo. Pre-treatment breast tissue was obtained from initial diagnostic core biopsy and post-treatment breast tissue was obtained from surgical excision specimen. Blood was obtained prior to surgery to assess serum lapatinib level. Participants kept a daily symptom assessment log and had a cardiac assessment at baseline and prior to surgery. Patients were instructed to take drug up to and including the day before surgery. The dual primary endpoint for this study was change in proliferation in pre- versus post-treatment biopsies between the two treatment arms, as measured by Ki67 as well as toxicity assessment. Secondary endpoints included incidence of DCIS at surgery and modulation of tissue biomarker expression in growth factor receptors (EGFR, ErbB2); phosphorylated growth factor receptor (phospho-ErbB2); signal transduction markers (MAPK, phospho-MAPK); hormone receptors (ER, PR); and p27. Results:Twenty-two women (mean age: 51; range: 32-66) with HER2+ or EGFR+ DCIS were treated with lapatinib (1,000 or 1,500 mg) or placebo for 2–6 weeks prior to surgical excision. Ki67 expression was significantly decreased in the lapatinib treatment arms compared to placebo (p=0.0122). Diarrhea, fatigue, and skin reactions were notable adverse events that occurred predominately in the lapatinib arm compared to placebo. No grade 3 or 4 events related to the study drug were noted during the study. No changes were noted in cardiac function. DCIS was present in all surgical specimens in both arms. Invasive breast cancer was noted in 1 patient on lapatinib 1000mg and 3 patients on placebo. No statistically significant changes were noted in signal transduction biomarkers Conclusion:These results demonstrate the effectiveness of lapatinib in reducing proliferation in women with EGFR+ or HER2+ DCIS. Even low-grade toxicities can deter use of an agent in the prevention setting. This and the lack of a risk model for HER2+ and triple negative breast cancer make the development of larger scale clinical prevention trials of lapatinib for the prevention a challenge. Citation Format: Thomas PS, Contreras A, Pruthi S, Krontiras H, Rimawi M, Garber J, Wang T, Hilsenbeck SG, Vornik LA, Gilmer T, Friedman R, Heckman-Stoddard BM, Dunn B, Kuerer H, Brown PH. A phase II pre-surgical trial of lapatinib for the treatment of women with HER2 positive or EGFR positive ductal carcinoma in situ [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD3-07.

Abstract Purpose: Topotecan resistance can result from drug efflux by P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) as well as survival signals initiated by epidermal growth factor receptor family members. The present studies were done to determine the effect of combining topotecan and the dual epidermal growth factor receptor/HER2 inhibitor lapatinib in tissue culture, a murine xenograft model, and a phase I clinical trial. Experimental Design: The effects of lapatinib on topotecan accumulation and cytotoxicity in vitro were examined in paired cell lines lacking or expressing Pgp or BCRP. Antiproliferative effects of the combination were assessed in mice bearing HER2+ BT474 breast cancer xenografts. Based on tolerability in this preclinical model, 37 patients with advanced-stage cancers received escalating doses of lapatinib and topotecan in a phase I trial. Results: Lapatinib increased topotecan accumulation in BCRP- or Pgp-expressing cells in vitro, and the combination showed enhanced efficacy in HER2+ BT474 xenografts. In the phase I study, nausea, vomiting, diarrhea, and fatigue were dose limiting. The maximum tolerated doses were 1,250 mg/d lapatinib by mouth for 21 or 28 days with 3.2 mg/m2 topotecan i.v. on days 1, 8, and 15 of 28-day cycles. Pharmacokinetic analyses showed that combined drug administration resulted in decreased topotecan clearance consistent with transporter-mediated interactions. Seventeen (46%) patients had disease stabilization. Conclusions: The lapatinib/topotecan combination is well tolerated and warrants further study.