A phase 1b study of oral rapamycin (sirolimus) in patients with advanced malignancies

3510

Background: Rapamycin (R) analogues are being studied as cancer therapies since mTOR is recognized as a relevant target in several cancer types. However, R is readily available, has been well-studied in organ transplant patients, was the first recognized mTOR inhibitor, and demonstrates efficacy in preclinical cancer models. The aims of this study were to define R’s maximum tolerated dose (MTD), observed toxicities, dose-limiting toxicities (DLT), pharmacokinetics and effect on inhibition of phosphorylation of p70 S6 kinase (S6K) in peripheral T-cells (PTL). Methods: R was administered orally once weekly to successive cohorts of patients using an adaptive escalation design based on whole blood concentrations ([R]), using a validated HPLC procedure. S6K was assessed by stimulating CD3+ cells ex-vivo with PMA and ionomycin for 1 hour, followed by Western blot analysis using antibodies directed against phospho-Thr389 of S6K versus total S6K as a loading control. Results: 24 subjects have been enrolled in dose cohorts of 10 mg, 20 mg, 30 mg, and 60 mg. The mean [R] observed on day 2 of week 1 (24 hr after 1st dose) was 5.5±2.7, 11.6±6.0 and 22.6±10.7 ng/mL, for dose levels 10 mg, 20 mg and 30 mg, respectively. [R] decreased by ∼50% by day 4 of week 1 (2.7±1.0, 6.9±4.0 and 11.0±7.7 ng/mL, respectively). By day 1 of week 2 (prior to the next dose of R), [R] had decreased below the limit of quantitation (2 ng/mL) for all subjects at 10 mg, 3 of 7 at 20 mg, and 4 of 6 at 30 mg. Preliminary analysis suggests that sustained phospho-S6K inhibition was achieved in some patients at 30 mg. The most common toxicities observed included nausea (50%), diarrhea (42%), asthenia (38%), hyperglycemia (58%), anemia (46%), and lymphopenia (33%). DLTs observed include 1 patient with grade 3 pneumonia at 20 mg, 1 patient with grade 3 dehydration at 30 mg, and 1 patient with grade 3 asthenia at 60 mg. Stable disease has been observed in 46% of evaluable patients. Conclusions: R can be feasibly administered orally on a once weekly schedule with a similar toxicity and pharmacokinetic profile compared with other mTOR inhibitors. Preliminary evidence suggests that prolonged suppression of phospho-S6K in PTL is possible at well-tolerated doses.

No significant financial relationships to disclose.

Phase I study of rapamycin (R) in combination with CYP3A4 modifier, ketoconazole (K), in patients with advanced malignancies

3061

Background: R is currently FDA approved for the treatment of renal allograft rejection but mTOR is a relevant target in several cancer types. K, a CYP3A4 inhibitor, increases the area under the concentration curve (AUC) of R and co-administration of R and K can overcome poor R bioavailability and decrease costs substantially. The aims of this study were to find the maximum tolerated dose (MTD) and dose-limiting toxicities (DLT) of R administered weekly in combination with K and describe the pharmacokinetics (PK) of the combination in patients with advanced malignancies. Methods: R and K were administered concurrently to successive cohorts of patients. R starting dose was 1 mg once weekly and was escalated by 1 mg per dose level. K was administered at a constant dose of 200mg BID 1 day prior to each R dose then 200 mg QD on the next 3 consecutive days. Results: 34 subjects (median age 60 years) have been enrolled. The highest dose of R administered thus far was 5mg without DLT. Most frequent toxicities observed of any grade included hyperglycemia (41%), lymphopenia (35%), hyperlipidemia (35%), fatigue (29%), anemia (26%), anorexia (24%), and nausea (24%). Observed grade 3 toxicities included 2 patients with lymphopenia, 2 patients with elevated transaminases, and 1 patient each with emesis and hyperglycemia. One patient experienced grade 3 confusion likely due to a drug-drug interaction of K with concomitant psychotropic medications. PK analysis of the first 2 dose levels confirms that K significantly increases Cmax and AUC of R ( Table ). R Cmax (with K) averaged 22.5 (11.7) and 27.4 (7.9) (mean/SD) ng/ml at the 1 and 2 mg dose levels, respectively. R AUC (with K) averaged 408.9 (225.4) and 663.8 (201.8) (mean/SD) ng*h/ml at the 1 and 2 mg dose levels, respectively. Conclusions: Low dose weekly R plus K results in potentially efficacious concentrations, as demonstrated by classic mTOR inhibitor toxicity. Higher doses on this schedule without K are probably also feasible, but would have higher costs.

[Table: see text]

No significant financial relationships to disclose.

A phase 1, dose-escalation trial of STA-5312, a microtubule inhibitor with a novel binding site, in advanced or metastatic solid malignancies

13040

Background: STA-5312 is a novel microtubule inhibitor with a distinct binding site from other agents such as vincristine, colchicine, or paclitaxel, which has demonstrated antitumor activity against a range of solid tumors in chemotherapy-resistant cancer. Methods: The trial assessed the safety, toxicity, pharmacokinetics (PK) and maximum tolerated dose (MTD) level of STA-5312 when administered as an IV infusion weekly for the first 3 weeks of a 4 week cycle. Assessment of activity is a secondary objective. The starting dose level was 6mg/m2. Dose escalation was based on evaluation of toxicity through the first cycle, with dose doubling in cohorts of 1–2 patients (pts) until a grade (gr) 2 or greater toxicity occurred, followed by at least 3 pts/cohort and 50% dose escalations. After a dose limiting toxicity (DLT), cohorts were expanded to at least 6 pts and subsequent escalations limited to 33%. The dose below the lowest dose at which 1/3 of 6 or more patients show DLT will be declared the MTD. PK sampling was performed during cycle 1. Results: To date, 25 pts have been treated: median age 58 years (35–77), ECOG performance status of 0–2, and median treatment duration 43 days. No serious drug-related toxicity was observed until a DLT (ataxia) was reported in the only patient treated at 64mg/m2, leading to de-escalation to 48 mg/m2, where the only patient experienced aphasia and ataxia. Enrollment is being expanded at a lower dose level of 32 mg/m2. Other adverse events attributable to STA-5312 include (>10%) anemia, fatigue, constipation, nausea, and anorexia. Exposure (AUC) was linear with respect to dose. Five patients have had disease stabilization. Conclusions: STA-5312 appears to be well tolerated when given weekly in doses up to 32mg/m2. The MTD has not been determined and enrollment is ongoing.

[Table: see text]

Blood pressure (BP) as a biomarker for sorafenib (S), an inhibitor of the vascular endothelial growth factor (VEGF) signaling pathway

2035

Background: Hypertension is a commonly reported toxicity of agents that inhibit the VEGF signaling pathway (VSP). This new class of cancer therapeutics has broad activity, but optimal dosing methods and integration into established treatment regimens could be enhanced by identification of reliable biomarkers. S, a new treatment for advanced renal cell carcinoma, is an orally available inhibitor of multiple VSP kinases including Raf-1 and VEGFR2. To characterize the chronicity and interindividual variability of BP responses to VSP inhibition we collected serial, standardized measures of BP and concurrent steady-state plasma concentrations ([plasma]) of S, from 30 patients (pts). Methods: Pts with advanced solid tumors, ECOG performance status < 2, and screening BP ≤ 140/90 mmHg on no more than one antihypertensive agent took 400mg S twice daily. Prior to therapy and at 3 time points after steady state [plasma] of drug was achieved, pts underwent 24-hour ambulatory BP monitoring with the SunTech Oscar PowerPack 2 (SunTech Medical, Morrisville, North Carolina). Readings were collected every 15 minutes during daytime hours and every 45 minutes overnight. Results: Unweigthed mean and standard deviations (sd) of systolic (SBP) and diastolic (DBP) 24-hr BP measurements were calculated for each pt. for the sessions pre-therapy and when steady state [plasma] S was reached (between days 6–10 after starting treatment). The differences in mean BPs between the two sessions were compared with (and p values reported for) paired t-tests. Regression analysis of [plasma] of S with either DBP or SBP, or change in DBP or SBP, with main effect and interaction terms for albumin, age, and sex revealed no significant correlation between S [plasma] and BP response. Conclusions: BP elevation is a biomarker for VSP inhibition. The known variability (coefficient of variation = 70%) in total S steady state plasma concentrations did not account for the observed variability in BP response.

[Table: see text]

[Table: see text]