Šikić, Branimir I.

Abstract CD27, a costimulatory molecule on T cells, induces intracellular signals mediating cellular activation, proliferation, effector function, and cell survival on binding to its ligand, CD70. Varlilumab, a novel, first-in-class, agonist immunoglobulin G1 anti-CD27 antibody, mediates antitumor immunity and direct killing of CD27+ tumor cells in animal models. This first-in-human, dose-escalation, and expansion study evaluated varlilumab in patients with hematologic malignancies. Primary objectives were to assess safety and the maximum tolerated and optimal biologic doses of varlilumab. Secondary objectives were to evaluate pharmacokinetics, pharmacodynamics, immunogenicity, and antitumor activity. In a 3 + 3 dose-escalation design, 30 patients with B-cell (n = 25) or T-cell (n = 5) malignancies received varlilumab (0.1, 0.3, 1, 3, or 10 mg/kg IV) as a single dose with a 28-day observation period, followed by weekly dosing (4 doses per cycle, up to 5 cycles, depending on tumor response). In an expansion cohort, 4 additional patients with Hodgkin lymphoma received varlilumab at 0.3 mg/kg every 3 weeks (4 doses per cycle, up to 5 cycles). No dose-limiting toxicities were observed. Treatment-related adverse events, generally grade 1 to 2, included fatigue, decreased appetite, anemia, diarrhea, and headache. Exposure was linear and dose-proportional across dose groups and resulted in increases in proinflammatory cytokines and soluble CD27. One patient with stage IV Hodgkin lymphoma experienced a complete response and remained in remission at >33 months with no further anticancer therapy. These data support further investigation of varlilumab for hematologic malignancies, particularly in combination approaches targeting nonredundant immune regulating pathways. This trial was registered at www.clinicaltrials.gov as #NCT01460134.

3044 Background: XL647 is an orally bioavailable small molecule inhibitor of multiple receptor tyrosine kinases involved in tumor cell growth, angiogenesis, and metastasis, including EGFR (erbB1), erbB2, VEGFR2/KDR, and EphB4. Methods: Patients (pts) with ASM were enrolled in successive cohorts to receive XL647 orally as a single dose on day 1 with PK sampling, followed by 5 continuous daily doses starting on day 4 with additional PK sampling. Pts then continued to receive XL647 for 5 consecutive days, followed by a break, with cycles repeating every 14 days. Tumor imaging was conducted at baseline, after the first 3 or 4 cycles, and then after every 4 cycles. Pts were allowed to stay on-study in the absence of unacceptable toxicity until evidence of disease progression. Results: A total of 37 pts have been treated across 9 dose levels to date: 0.06, 0.12, 0.19, 0.28, 0.39, 0.78, 1.56, 3.12, 4.68, and 7.0 mg/kg. One pt at 3.12 mg/kg had a dose limiting toxicity (DLT) of asymptomatic QTc prolongation on electrocardiogram, resulting in expansion of that cohort. The first two pts who received 7.0 mg/kg experienced DLTs of grade 3 diarrhea, requiring dose reduction. Both pts from the 7.0 mg/kg cohort tolerated 4.68 mg/kg well. Expansion of the 4.68 mg/kg cohort to 6 pts occurred without further DLTs and this is considered the maximum tolerated dose (MTD). One serious adverse event, grade 4 pulmonary embolism, was considered possibly related to study treatment in a pt dosed at 0.28 mg/kg. PK analysis indicates that XL647 shows approximately dose-proportional exposure, a mean time to maximal concentration (tmax) of 6–9 hours and an elimination half-life of 50–70 hours. To date, 1 pt (non-small cell lung cancer [NSCLC]) from cohort 1 had a partial response and 7 others (NSCLC [2], chordoma [2], adenoid cystic carcinoma, adrenocortical carcinoma, colorectal) have had prolonged stable disease (>3 months). Conclusions: XL647 has been well tolerated. An MTD of 4.68 mg/kg oral dosing for 5 consecutive days every 14 days has been established. Exploration of additional dosing schedules is ongoing, including continuous daily dosing. [Table: see text]

14044 Background: XL647 is an orally bioavailable small molecule inhibitor of multiple receptor tyrosine kinases involved in tumorigenesis, angiogenesis, and metastasis, including EGFR/ErbB1, ErbB2/HER2, VEGFR2/KDR, and EphB4. In a previous Phase I study, the MTD was 350 mg when XL647 was dosed orally for 5 consecutive days every 14 days. Of 41 pts treated, one pt with NSCLC achieved a PR and 14 pts had prolonged stable disease (3.5–14+ months). The purpose of the present study is to determine the MTD of XL647 administered orally on a continuous daily schedule. Methods: Pts are enrolled in successive cohorts to receive XL647 daily for repeated 28 day cycles. PK sampling is performed to determine Cmax, and AUC at each dose level. Plasma samples are analyzed by ELISA for mechanism-of-action related molecules. Eyebrow hair bulbs are being evaluated by IHC to monitor effects of XL647 on signal transduction pathways downstream of EGFR. Tumor response is assessed every 8 weeks by RECIST. Pts remain on study until PD or unacceptable AEs. Results: Twelve pts have been enrolled. The starting dose was 75 mg (n=3) and has been escalated to150 mg (n=3), 200 mg (n=3) and 300 mg (n=3). To date, dose escalation continues as no DLTs have occurred and the MTD has not been determined. Ten pts remain on study, including 4 with stable disease for at least 3 months. In cohort 2, eyebrow samples from 3 pts were analyzed. XL647 caused a significant reduction in the phosphorylation of the EGFR downstream signaling kinases AKT (up to 73%) and ERK (up to 78%) in 2/3 and 3/3 pts, respectively. Preliminary analysis of potential plasma protein biomarkers from pts in cohorts 1 and 2 showed a trend towards upregulation of PlGF plasma levels in 4/6 pts during XL647 treatment. Conclusions: XL647 is well-tolerated when administered daily at doses tested to date. Dose escalation will continue until the MTD is defined. Analysis of eyebrow samples demonstrated its feasibility as a potential surrogate epidermal tissue for assessing inhibition of EGFR downstream targets by XL647. Updated safety, PK and pharmacodynamic results will be presented. [Table: see text]

Purpose CD27, a costimulatory molecule on T cells, induces intracellular signals that mediate cellular activation, proliferation, effector function, and cell survival upon binding to its ligand, CD70. Varlilumab is a novel, first-in-class, agonist CD27 antibody that stimulates the CD27 pathway, which results in T-cell activation and antitumor activity in tumor models. This first-in-human, dose-escalation and expansion study evaluated the safety, pharmacology, and activity of varlilumab in patients with advanced solid tumors. Methods In a 3 + 3 dose-escalation design (n = 25), patients received a single dose of varlilumab (0.1, 0.3, 1.0, 3.0, or 10 mg/kg intravenously) with a 28-day observation, followed by up to five multidose cycles (one dose per week for 4 weeks), depending on tumor response. Expansion cohorts were initiated at 3.0 mg/kg in patients with melanoma (n = 16) and renal cell carcinoma (RCC; n = 15). Primary objectives were to assess the safety and the maximum tolerated and optimal biologic doses of varlilumab. Secondary objectives were to evaluate the pharmacokinetics, pharmacodynamics, and clinical antitumor activity of varlilumab. Results Exposure to varlilumab was linear and dose proportional across dose groups. Only one patient experienced a dose-limiting toxicity—grade 3 transient asymptomatic hyponatremia at the 1.0-mg/kg dose level. Treatment-related adverse events were generally grade 1 or 2 in severity. Evidence of biologic activity consistent with CD27 stimulation—chemokine induction, T-cell stimulation, regulatory T cell depletion—was observed at all dose levels. A patient with metastatic RCC experienced a partial response (78% shrinkage, progression-free survival > 2.3 years). Eight patients experienced stable disease > 3 months, including a patient with metastatic RCC with progression-free survival of > 3.9 years. Conclusion Dose escalation of varlilumab to 10 mg/kg was well tolerated without identification of a maximum tolerated dose. Varlilumab was biologically and clinically active.

Purpose To determine whether adding the multidrug resistance gene-1 (MDR-1) modulator valspodar (PSC 833; Novartis Pharmaceuticals, Hanover, NJ) to chemotherapy provided clinical benefit to patients with poor-risk acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS). Patients and Methods A phase III randomized study was performed using valspodar plus mitoxantrone, etoposide, and cytarabine (PSC-MEC; n = 66) versus MEC (n = 63) to treat patients with relapsed or refractory AML and high-risk MDS. Results For the PSC-MEC versus MEC arms, complete response (CR) was achieved in 17% versus 25% of patients, respectively (P = not significant). For patients who had not received prior intensive chemotherapy (ie, with secondary AML or high-risk MDS), the CR rate was increased—35% versus 15% for the remaining patients (P = .018); CR rates did not differ between treatment arms. The median disease-free survival in those achieving CR was similar in the two arms (10 versus 9.3 months) as was the patients’ overall survival (4.6 versus 5.4 months). The CR rates in MDR+ (69% of patients) versus MDR− patients were similar for those receiving either chemotherapy regimen (16% versus 24%). The CR rate for unfavorable cytogenetic patients (45% of patients) was 13% compared to the remainder, 28% (P = .09). Population pharmacokinetic analysis demonstrated that the clearances of mitoxantrone and etoposide were decreased by 59% and 50%, respectively, supporting the empiric dose reductions in the PSC-MEC arm designed in anticipation of drug interactions between valspodar and the chemotherapeutic agents. Conclusion CR rates and overall survival were not improved by using PSC-MEC compared to MEC chemotherapy alone in patients with poor-risk AML or high-risk MDS.