Targeted Therapy With Lapatinib in Patients With Recurrent Pituitary Tumors Resistant to Standard Therapy

Overview

This study focuses on new therapies for a challenging disease in pituitary medicine, that of aggressive pituitary tumors which have limited therapeutic options beyond standard surgical, radiotherapy, and select medical therapies, each incurring significant morbidity and mortality, and each not optimally effective. To improve this gap in knowledge, we seek to translate findings from the laboratory into clinical practice and hone in on therapies directed at pituitary molecular targets, namely ErbB receptors. We have shown that human prolactinomas express nuclear EGFR and membranous ErbB2, ErbB3 and ErbB4, and expression correlates with tumor invasion. Pituitary tumor cell lines transfected with EGFR and ErbB2 translated to downstream effects on prolactin (PRL) gene expression and secretion,as well as cell proliferation. Animal models implanted with these cell lines developed larger tumors and PRL elevations. Treatment with ErbB tyrosine kinase inhibitors (TKIs) led to regression of tumors xenografted into these animals and attenuated PRL secretion. Primary culture of human prolactinomas confirmed expression of ErbB receptors and inhibitory effects of TKIs on PRL secretion and cell proliferation. Based on these exciting preliminary data, the objective of this new proposal is to conduct a Phase IIa clinical trial as a trenchant test of our translational hypothesis that tyrosine kinase inhibition constitutes highly effective targeted biologic therapy for these hitherto refractory pituitary adenomas. Specifically, our aims are to test the: 1) efficacy of TKI therapy with a clinical trial; 2) threshold level of tumor receptor expression to achieve TKI clinical response. Nineteen subjects will be treated with lapatinib for 6 months in combination with their current dopamine agonist therapy, with monthly measurements of PRL levels and MRI imaging every 3 months to evaluate the primary endpoints of achieving 40% reduction in tumor size and 50% reduction in PRL and secondary endpoints of radiologic stabilization and/or reduction and PRL normalization. Mean ErbB receptor protein expression will be compared between responders to lapatinib and non-responders by immunohistochemistry in pituitary tumor samples of these subjects collected from prior surgeries.

PURPOSE The drug Lapatinib has been shown to inhibit both epidermal growth factor receptor (EGFR) and erbB2 tyrosine kinases resulting in an effective slowing of disease progression in breast cancer. It has also been demonstrated that erbB is overexpressed in human pituitary adenomas. The investigators are therefore assessing tumor size stabilization and pituitary tumor secretory profiles during the course of a six month therapy of lapatinib. The purpose of this trial will be to estimate the activity of lapatinib in slowing the growth rate of pituitary tumors. Lapatinib is an FDA approved drug used to treat breast cancer. However, in this study, the drug will be used to treat pituitary cancer. STUDY POPULATION This study will recruit patients from the Pituitary Center at CSMC who are over the age of 18 that have a recurrent nonfunctioning adenoma after at least one surgical resection as well as patients with prolactinomas who are resistant to dopamine agonist therapy and patients with recurrent Cushing's disease. PARTICIPANT'S JOURNEY THROUGH THE RESEARCH The principal investigator (PI) or co-investigator will determine patients' potential eligibility for the study based on inclusion and exclusion criteria. The PI or the co-investigator will then approach subjects with recurrent nonfunctioning adenomas or prolactinomas resistant to dopamine agonist therapy or recurrent Cushing's disease during a visit in the clinic office and ask if these subjects would be interested in participating in this study. If the subjects express interest, they will be given the consent form to review. They will be encouraged to review it with family, friends, and/or other physicians. The PI, co-investigators, or research nurse will be available for any questions the subjects might have. If the subjects are still interested, they will be asked to sign and return the consent form to the office and a study visit will be scheduled. The PI, co-investigator, or member of study staff may also attempt to contact current patients by phone to assess interest in participating in the study. The purpose and overall structure of the study will be discussed with the possible participant. They will be reminded that the study is strictly voluntary and that their involvement or disinterest in the study will not affect their ongoing care. If the patient is interested they will be mailed a consent to review and will be asked to call the center to schedule an appointment to further discuss the study if they decide they are interested. Each participant will undergo 8 visits of the course of the study. Each participant will have a baseline visit where a medical history will be taken, a physical, visual field test, electrocardiogram (ECG), echocardiogram (ECHO), and blood draw will be performed. At this point lapatinib therapy will begin and the patients will be asked to take the drug daily for the next six months. Patients will take Lapatinib 1250 mg daily (orally), which is the standardized dose used to treat breast cancer patients. Visit 2 will be 1 month after the participant has started lapatinib. At visit 2 all participants will receive a physical exam, a history will be taken, an ECG will be performed, and a blood draw will occur. Visit 3 will be 2 months after starting lapatinib. A physical exam and history will be performed along with an ECG and echocardiogram and blood draw. Visit 4 will be 3 months after starting lapatinib. A physical, history, blood draw, ECG, visual field test, and a magnetic resonance imaging (MRI) of the pituitary will be performed. Visit 5 will occur 4 months after starting lapatinib. A physical exam and history along with a blood draw and ECG and echocardiogram will occur. Visit 6 will be 5 months after starting lapatinib. A physical exam, history, ECG, and a blood draw will occur. Visit 7 will occur 6 months after the start of lapatinib. A physical exam, history, blood draw, visual field test, ECG, echocardiogram and MRI of the pituitary will occur. At this point lapatinib will be discontinued. Visit 8 will occur 1 month after visit 7 and a physical exam, history, blood draw, and ECG and and echocardiogram will occur.