Enzastaurin, an Oral Serine/Threonine Kinase Inhibitor, As Second- or Third-Line Therapy of Non–Small-Cell Lung Cancer

Abstract

PurposeEnzastaurin, an oral serine/threonine kinase inhibitor, suppresses protein kinase C (PKC) and protein kinase B/AK transforming (AKT) signaling, induces tumor cell apoptosis, and inhibits proliferation and angiogenesis. Increased PKC and AKT activity is associated with poor prognosis in non–small-cell lung cancer (NSCLC). This phase II trial of enzastaurin was conducted to determine the 6-month progression-free survival (PFS) rate in advanced, metastatic NSCLC.Patients and MethodsPatients with metastatic (stage IV and wet IIIB) NSCLC, Eastern Cooperative Oncology Group performance status ≤ 2, and ≤ two prior systemic regimens (including one or more platinum-based chemotherapy regimens) received 500 mg of enzastaurin administered once daily.ResultsFifty-five patients were enrolled (55% male patients, 45% female patients; median age, 63 years; range, 44 to 82 years; 78% of patients having stage IV disease). Adenocarcinoma was the most common diagnosis (65%). Prior therapies included radiotherapy (73%) and epidermal growth factor inhibitors (29%). Median PFS was 1.8 months (95% CI, 1.7 to 1.9). Six-month PFS rate was 13% (95% CI, 3.9% to 21.5%). Median overall survival (OS) was 8.4 months (95% CI, 6.0 to 13.6 months). The 12-month OS rate was 44% (95% CI, 30.5% to 57.3%). Nineteen patients (35%) had stable disease. No objective responses were observed. Seven patients (13%) had PFS ≥ 6 months, three of whom continued for more than 10 months. The most common toxicity was fatigue (grade ≤ 3; n = 17). Grade 3 or worse toxicities were fatigue (n = 2), thromboembolism (n = 1), ataxia (n = 1), and anemia (n = 1). Two patients discontinued treatment because of drug-related fatigue and dizziness. Five patients died while enrolled in the study (non drug-related).ConclusionAlthough the primary end point of a 20% PFS rate was not achieved, 13% of the patients had PFS for ≥ 6 months. Given the tolerability and survival data, evaluation of enzastaurin in combination with cytotoxic drugs is warranted in NSCLC.