Eligibility criteria included patients ≥18 years of age; estimated survival of >12 weeks; Karnofsky performance status ≥60; and a histologically confirmed, newly diagnosed GBM or GS with a biopsy or resection ≤5 weeks prior to treatment. Patients must have recovered from the effects of surgery and had adequate organ function. All patients practiced birth control during and for 3 months after treatment.
Exclusion criteria included prior cranial RT, chemotherapy, or carmustine wafers; any anticoagulant therapy (permitted, if required, after starting treatment with careful monitoring); history of any other cancer (except nonmelanoma skin cancer or carcinoma in situ of the cervix) unless in complete remission without therapy for a minimum of 3 years; any significant medical illnesses that could not be adequately controlled or would compromise the patient's ability to tolerate the treatment; and an electrocardiogram demonstrating clinically significant arrhythmia that was symptomatic or required treatment. Patients must have discontinued enzyme-inducing anti-epileptic drugs ≥2 weeks prior to treatment.
All patients or their designated surrogates signed a consent form approved by the participating institution's ethical review board. The study was conducted in accordance with the Declaration of Helsinki and good clinical practices.
Study Design and Treatment Plan
This was a single-institution, phase I, dose-escalation study of enzastaurin administered with temozolomide, during and following RT, in patients with newly diagnosed GBM or GS (Figure ). Radiotherapy was administered in 1.8–2.0 Gy/d fractions for 5 d/wk (1.8–2.0 Gy × 30 fractions) for 6 weeks. A total of 45.0 Gy was delivered to the clinical tumor volume, consisting of T2-bright edema plus a 2-cm margin, or, if no edema, the contrast-enhancing lesion plus a 2.5-cm margin. An additional boost of 14.4 Gy was delivered to the gross tumor volume, consisting of the contrast-enhancing lesion plus a 1-cm margin. The dose to the optic chiasm and brainstem was limited to ≤54.0 Gy, the dose to one or preferably both retinas was limited to ≤50.0 Gy, and the dose to the cervical spine was limited to ≤45.0 Gy.
Study schema for the phase I clinical trial. *Patients also received ondansetron 4–8 mg or granisetron 1–2 mg for prevention of nausea associated with temozolomide.
During RT, patients took 75 mg/m2 oral temozolomide daily, with water, on an empty stomach, followed by a meal and either 250 or 500 mg enzastaurin within 30 minutes after the meal (at the same time each day). Enzastaurin and temozolomide were taken from the night before the first dose of RT to the night before the last dose of RT. At the conclusion of RT, patients took a 14–21 day break from enzastaurin and temozolomide. If ≤1 of the first 6 patients experienced a dose-limiting toxicity (DLT) and neuro-imaging showed no sign of tumor progression, patients completed one adjuvant cycle (28 days) of enzastaurin (250 mg daily) + temozolomide (200 mg/m2/d for 5 days). If there were no DLTs, patients continued subsequent adjuvant enzastaurin + temozolomide at the same doses. Adjuvant treatment was planned for 12 cycles (one cycle = 28 days). Patients were discontinued for tumor progression, unacceptable toxicity, and noncompliance. Treatment could continue beyond 12 cycles at the discretion of the investigator and sponsor.
Dose escalations were planned in 2 cohorts of 6 patients. The maximum tolerated dose (MTD) of enzastaurin was defined as the dose at which <33% patients experienced a DLT. Toxicities were graded according to the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE) version 3.0. DLTs were defined as any of the following events occurring during concurrent RT + enzastaurin + temozolomide or during the first adjuvant cycle that were attributable to enzastaurin or enzastaurin + RT and/or temozolomide: Grade ≥3 thrombocytopenia; Grade 4 anemia or neutropenia; nonhematologic grade ≥3 toxicity; or Grade 4 radiation-induced skin changes.
In the initial cohort, up to 6 patients were to receive 250 mg enzastaurin during concurrent RT + enzastaurin + temozolomide. If ≥2 of the 6 patients experienced DLTs during RT + enzastaurin + temozolomide or during the first adjuvant cycle, then the study would be deemed unsafe and stopped.
If ≤1 of the 6 patients in cohort 1 experienced a DLT during RT and the first adjuvant cycle, up to 6 more patients were entered in cohort 2 at an escalated dose of 500 mg enzastaurin. The timing of evaluations, dosing, and monitoring were the same as those for cohort 1.
Dose modifications were based on the expected toxicities for either temozolomide or enzastaurin. Enzastaurin was omitted for any of the following possibly related events: absolute neutrophil count (ANC) <0.5 × 109/L for >7 days, ANC <1.0 × 109/L with fever (temperature of 101°F/38.5°C), platelet count <25 × 109/L, or clinically relevant grade ≥3 nonhematologic toxicity. If the toxicity resolved to Grade ≤1 or the patient's baseline, the patient resumed therapy at 250 mg daily. If not, the patient was discontinued. For Grade ≥3 transaminase elevations that returned to baseline by day 1 of the next cycle, treatment resumed without delay or dose reduction. For patients on 500 mg enzastaurin, the dose was re-escalated to the 500 mg level if the toxicity did not recur after 28 days of therapy at 250 mg.
During RT, temozolomide was reduced to 50 mg/m2/d for Grade ≥3 hematologic toxicity. If a subsequent Grade ≥3 hematologic toxicity occurred after a dose reduction, temozolomide was discontinued for the remainder of RT. If a dose reduction was required during RT, the dose during the first adjuvant cycle was reduced to 150 mg/m2. The dose for subsequent adjuvant cycles was increased to 200 mg/m2 if no Grade ≥3 hematologic toxicity occurred during the first adjuvant cycle.
Temozolomide was delayed in the adjuvant cycles until the following criteria were met: ANC ≥1.5 × 109/L; platelet count ≥100.0 × 109/L; and related nonhematologic toxicities returned to Grade ≤1 (except for alopecia, nausea, and vomiting). If the hematologic criteria were met, temozolomide was reduced to the next lower dose level. If the ANC remained <1.5 × 109/L or the platelet count was <100.0 × 109/L at 4 weeks, despite two dose reductions (to 100 mg/m2), temozolomide was discontinued. Patients who experienced Grade ≥3 toxicity with a dose of 100 mg/m2 discontinued temozolomide, but continued enzastaurin.
If a Grade 5 event occurred during RT or the first adjuvant cycle, then accrual would be suspended.
A complete history, physical, neurological examination, laboratory tests, and baseline MRI or CT scan were done within 14 days of starting treatment. The attending neuro-oncologist assessed pre- and postoperative imaging to determine the extent of resection. Steroid doses had to be stable for 5 days preceding the MRI.
A complete blood count with differential was performed every 2 weeks during RT and in weeks 3 and 4 of each adjuvant cycle of temozolomide. Chemistry was assessed every 4 weeks. Patients had clinical assessment 4 weeks into RT, 2–3 weeks after RT, and at the conclusion of each adjuvant cycle. Radiographic assessments were also performed 2 weeks after RT and every 8 weeks thereafter for the duration of treatment. All evaluable tumor sites were assessed using the same techniques as baseline. The Macdonald Criteria were used to evaluate radiological progression.19
Plasma samples were collected for pharmacokinetic evaluation of enzastaurin at steady state, when administered either alone (on day 22 of adjuvant cycle 1) or with temozolomide (day 5 of adjuvant cycle 2), at predose, and 2, 4, 6, and 24 hours postdose. Samples were assayed for enzastaurin and its metabolite, LY326020, using high-performance liquid chromatography with tandem mass spectrometry (LC/MS/MS) as previously described (Advion BioSciences, Inc.). Pharmacokinetic parameters were calculated using noncompartmental methods from the plasma concentration–time profiles of enzastaurin and its metabolite with WinNonlin Enterprise 5.0.1 (Pharsight).