A multicenter phase II study of darinaparsin in relapsed or refractory Hodgkin's and non‐Hodgkin's lymphoma
Authors: Peter J. Hosein, Michael D. Craig, Martin S. Tallman, Ralph V. Boccia, Brian L. Hamilton, Jonathan J. Lewis, Izidore S. Lossos
Journal: American Journal of Hematology (2011)

Darinaparsin is a novel organic arsenic compound that is being developed to improve the efficacy and therapeutic index of arsenic as an antineoplastic agent. It has activity in preclinical models of hematological malignancies and we set out to test it in patients with refractory lymphoma. In this multicenter, Phase II trial, patients with relapsed or refractory Hodgkin (HL) and non-Hodgkin lymphoma (NHL) were treated with darinaparsin 300 mg/m2 intravenously daily for five consecutive days every 28 days, for up to six cycles. The primary endpoint was the overall response rate. Twenty-nine heavily pretreated patients with lymphoma (22 with NHL and 7 with HL) were enrolled. There was one complete response (CR), one unconfirmed CR (CRu), three partial responses (PRs), and four with stable disease (SD), with an overall response rate of 17% (95% confidence interval (CI) 6–36%). Among the seven patients with peripheral T-cell lymphoma (PTCL), there was one CR, one CRu, and two with prolonged SD. The most common toxicities were fatigue, nausea, diarrhea, and anemia. Darinaparsin was safe and showed preliminary activity in this heavily pretreated population of relapsed/refractory lymphoma patients. Encouraging responses were seen in PTCL and further study in this subtype is planned. An estimated 74,030 people in the United States are diagnosed with HL or NHL every year with a global disease burden of approximately 350,000 new cases per year [1, 2]. Major advances have been made over the last few decades in the treatment of these disorders in the form of combination chemotherapy, monoclonal antibody therapy, and stem cell transplantation [3-5], resulting in cure for a substantial proportion of cases. However, there remains a subgroup of patients who do not respond to standard therapy or relapse after an initial response. PTCL accounts for 7–10% of NHL cases and is a particularly unfavorable subtype [6]. Combination chemotherapy with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) is the usual treatment approach for PTCL, but outcomes are generally poor even with more intensive regimens [7]. Darinaparsin (N-[S-(dimethylarsino)-N-L-gamma-glutamyl-L-cysteinyl]-glycine; S-dimethylarsino-glutathione, ZIO-101, Zinapar™) is a novel organic arsenic molecule consisting of dimethylated arsenic conjugated to glutathione [8]. Darinaparsin achieves higher intracellular levels compared to inorganic arsenic trioxide (ATO), and has activity in vitro against leukemia, myeloma, lymphoma, and various solid tumor cell lines [9, 10]. Darinaparsin's multifaceted mechanisms of action include disruption of mitochondrial functions, increase in reactive oxygen species (ROS), and effects on signal transduction. Darinaparsin induces cell cycle arrest and apoptosis and has potent anti-angiogenic activity [11]. Unlike ATO, darinaparsin lacks affinity for the ABCC1 efflux proteins and is cytotoxic to certain ATO-resistant cell lines [12]. While other arsenicals have been used clinically, particularly for the treatment of acute promyelocytic leukemia, concerns about cardiac, hepatic, and central nervous system toxicities have limited their use [13-15]. Darinaparsin is being developed to broaden the clinical utility of arsenic while also improving its safety profile [9]. The safety, pharmacokinetics, and efficacy of darinaparsin have been evaluated in trials in patients with hematologic cancers [16], refractory solid tumors [17], multiple myeloma [18], and hepatocellular carcinoma [19]. Based on preclinical studies in hematological malignancies and a favorable safety profile from prior clinical trials, we designed this study to evaluate the safety and efficacy of darinaparsin in patients with hematologic cancers, and are reporting on a subset of the study population with relapsed HL or NHL. A total of 29 patients (22 with NHL and 7 with HL) were enrolled between January 2007 and January 2009. The database was locked for analysis at the end of December 2010. The median follow-up was 6.4 months (range 0.9–35.7 months). The patient characteristics are listed in the Supporting Information Table 1. A total of 90 cycles of darinaparsin were administered with a median of two cycles per patient (range 1–20). Two patients who had clinical benefit at the end of six cycles of therapy were allowed to continue with one patient receiving two additional cycles and one coming off study for progressive disease after completing cycle 20. The Supporting Information Table 2 summarizes the treatment and reasons for study discontinuation. There was one CR, one unconfirmed CR (CRu) and three PRs, corresponding to an overall response rate (ORR) of 17.2% (95% CI 5.9–35.8%). An additional four patients achieved SD. Among the seven evaluable patients with PTCL, there was one CR, one CRu, and two SD, giving an ORR of 28.6% (95% CI 3.7–71.0%). The patient who achieved a CRu met all the 1999 IWG criteria [20] for a CR including >75% reduction in the sum of the product of the diameters of the target lesions, but still had a residual lymph node mass more than 1.5 cm. Table I summarizes the prior therapies and survival for the patients who benefited from therapy. Among all patients enrolled, the Kaplan–Meier estimates for exploratory endpoints of median time to treatment failure (TTF) and overall survival (OS) was 1.8 months (95% CI 1.1–2.5) and 6.4 months (95% CI 0.0–13.6), respectively. For the nine patients with clinical benefit (CR, PR, or SD), the TTF and OS were 6.5 months (95% CI 6.2–6.8) and 9.7 months (95% CI 9.4–10), respectively. Among the seven patients with PTCL, the Kaplan–Meier estimates for the median TTF and OS were 3.6 and 6.4 months (95% CI 2.3–4.9 and 1.6–11.2), respectively. The Supporting Information Figure 1 shows the Kaplan–Meier survival curves for TTF and OS. Mean concentrations of arsenic after darinaparsin administration by a 1-hr infusion on study Days 1–5 of each cycle. Blood samples for PK analysis were collected from subjects enrolled in the extensive ECG monitoring cohort at the screening visit, just prior to and 1 hr after darinaparsin infusion on Days 1 and 5 of Cycles 1, 2, and 3, and at the end of treatment visit (28 ± 3 days after last infusion). Additional samples were collected 2 hr after infusion during Cycle 1. All patients experienced at least one adverse event (AE), of which 52% were investigator-assessed as being related to study therapy. Table II lists AEs that were reported in more than 10% of patients. Severe hematological toxicities were infrequent and there was only one episode of febrile neutropenia. The most frequently reported AEs were constitutional (fatigue and fever) and gastrointestinal (nausea, vomiting, and diarrhea). Eighteen patients experienced AEs of Grade 3 or higher with 4 judged by the investigators to be related to darinaparsin. These included fatigue, an increase in alkaline phosphatase, anemia, thrombocytopenia, and neutropenic fever. Three patients died during the first two cycles of therapy, and one died within 30 days of ending study treatment, all considered to be unrelated to study drug, and all due to disease progression. Three patients were taken off study due to AEs considered related to therapy; one patient had neutropenic fever (Grade 3), one had thrombocytopenia (Grade 4), and another had recurrent unsteady gait (Grade 2). Nine patients were included in the extensive electrocardiogram (ECG) monitoring cohort and had concomitant ECG and pharmacokinetic (PK) analysis done. Because of the low number of patients in this cohort, Cmax was the only PK parameter analyzed. The Cmax values varied between subjects for each time point with the highest standard deviation on Cycle 1, Day 5. Of the eight subjects with samples collected on Day 5 of Cycle 1, seven had higher darinaparsin concentrations on Day 5 compared with those on Day 1. For Cycles 2 and 3, all subjects had increased concentrations on Day 5 compared with those on Day 1. Mean Cmax values increased approximately twofold from Day 1 to Day 5 for each cycle. Mean concentrations of darinaparsin for all collection times are shown in Fig. 1. Although darinaparsin concentrations increased from Day 1 to Day 5, concentrations returned close to baseline levels by the start of the subsequent cycle. The mean Cmax calculated from samples taken 28 ± 3 days after the last dose of darinaparsin was also similar to baseline. One patient who had a normal corrected QT interval (QTc) at screening was later found on central review to have a Cycle 1 Day 1 pre-infusion QTc exceeding 450 msec. The number of patients with a QTc > 450 msec (Grade 1 prolonged QTc) increased to 4 and 6 at pre-infusion and post-infusion on Day 5, respectively (all cycles pooled). Among all patients and time-points, there was only one ECG with a QTc exceeding 480 msec (Grade 2 prolonged QTc); no ECGs had a QTc > 500 msec. The concentration: effect (C:E) fitted slope provided no evidence for prolonged QTc with increase in exposure suggesting that any potential for prolonged QT is not closely related to plasma concentration of the study drug. This Phase II clinical study reports the safety and efficacy of darinaparsin in patients with lymphoma. The responses seen in this trial were encouraging, especially since most of the patients enrolled were heavily pretreated, and had few other treatment options available. Five of these patients (17% of all patients and 27% of the evaluable patients) had a response with a median duration of response of approximately 5 months. Four patients (22%) had disease stabilization lasting for at least 3 months, with the longest being maintained for over 2 years. Although the numbers are small and clinical benefit was seen in a diverse range of histologies, a promising subgroup appeared to be PTCL, among whom the clinical benefit rate (CR, CRu, PR, and SD) was 80%. The dose of darinaparsin that was tested in this study was 300 mg/m2 intravenously daily for 5 days, on a 28-day cycle. Based on prior studies, the dose used in this study was termed the clinically effective dose and the results presented here confirm that this dose is active [18, 21]. PK data suggest that darinaparsin (as measured by arsenic concentration) did not accumulate or persist in the blood long-term and returned to near baseline following the final darinaparsin administration. Darinaparsin was generally well tolerated in this Phase II trial. Serious AEs related to therapy were infrequent and included expected hematological toxicities such as anemia and neutropenia, which were manageable. Gastrointestinal toxicities were common but were mild. Central nervous system effects were also observed, with dizziness being the most common and one patient experiencing recurrent unsteady gait, which resolved after study drug discontinuation. These observations are consistent with the neurological AEs seen in Phase I studies of darinaparsin. Although one-fifth of the patients with ECG data had Grade 1 or 2 prolonged QTc, these were all reversible and not clinically meaningful. There were no cases of QTc intervals greater than 500 msec, which is the threshold usually associated with higher risk for serious arrhythmias. To date, darinaparsin has not been associated with any serious prolongation of the QTc in any of the Phase I or Phase II trials reported. An overall trend for increase in QTc interval with time, relative to study baseline was noted. However, analysis of the C:E curve was not suggestive of a darinaparsin effect and these changes may have been reflective of the natural course of the disease or concomitant medications. This study provides preliminary evidence that darinaparsin is active and well tolerated in patients with multiple types of relapsed or refractory lymphoma, including patients presenting with bone marrow involvement. It is reasonable to hypothesize that the activity seen may have been more pronounced in a more favorable population such as patients who are newly diagnosed. Because of the promising responses seen in PTCL, efforts are currently underway to further test darinaparsin in this lymphoma subtype. This was a single-arm, open-label, optimal 2-stage, multicenter Phase II clinical trial of darinaparsin monotherapy in hematological malignancies. The primary objectives were to establish efficacy as measured by overall response rate and safety. Institutional review boards at each center approved the protocol, each patient provided written informed consent before treatment and the study was conducted in compliance with the Declaration of Helsinki. The study was registered at ClinicalTrials.gov under the identifier NCT00421213. Patients enrolled in this lymphoma subset had a histologically confirmed diagnosis of HL or NHL who had progressed after at least one prior line of therapy and had evaluable disease. Eligible patients had to be at least 3 weeks off any prior chemotherapy and had to have a life expectancy of at least 2 months. Additional inclusion criteria required patients to be at least 18 years old, have an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0–2, have adequate renal and hepatic function (serum creatinine and total bilirubin ≤ 2 times the upper limit of normal [ULN], alanine transaminase [ALT], and aspartate transaminase [AST] ≤ 3 times the ULN), and have the ability to give informed consent. Women of childbearing potential had to agree to use contraception throughout the study period. Patients were excluded if there was any history of cardiovascular disease with a New York Heart Association (NYHA) functional class ≥ 3, myocardial infarction within 6 months, uncontrolled cardiac arrhythmias other than asymptomatic atrial fibrillation, a QTc ≥ 450 msec, or second-degree atrioventricular (AV) block or left bundle branch block (LBBB). Patients with uncontrolled infections, prior seizures, significant neuropathology, confusion, dementia, or prior history of neurologic deficits (such as stroke) were also excluded. Pregnant or lactating women were not considered for participation. Darinaparsin was provided by ZIOPHARM Oncology Inc. (Boston, MA). It was administered daily at 300 mg/m2 for 1 hr intravenously (through a central venous catheter) for five consecutive days, and repeated on a 28-day cycle. Treatment was continued until unacceptable toxicity, disease progression, withdrawal of consent, or a maximum of six cycles of therapy. Patients who derived benefit from study therapy were allowed to continue beyond six cycles at the discretion of the investigator and sponsor. Patients were monitored at least once per week during treatment with physical examinations, AE assessments, and laboratory evaluations. AEs were graded according to the Common Terminology Criteria for AEs (CTCAE) version 3.0 [22]. Patients developing any Grade 4 AEs were withdrawn from the study. Patients with Grade 3 non-hematological AEs were allowed to go on to the next cycle with a reduced dose of 214 mg/m2, providing the observed toxicities resolved to less than or equal to Grade 1. If a scheduled cycle was delayed by more than 4 weeks, the patient was withdrawn from the study. Only one dose reduction was allowed per patient. At the discretion of the treating physician, patients who did not recover from AEs but were deriving benefit could be allowed to continue at the reduced dose. All patients had a baseline ECG at screening to exclude patients with QTc > 450 msec. ECGs were done on Days 1 and 5 of each cycle just prior to, and then 1 hr after the start of the infusion. ECGs were collected either singly, or in triplicate. The first 10 patients enrolled were entered into an "Extensive ECG Monitoring" cohort where an additional ECG was done 2 hr after the start of the infusion on days 1 and 5 of each cycle. All the patients in the extensive ECG monitoring cohort had blood samples drawn at the same time as ECGs for PK analysis. All patients had an ECG at the end-of-treatment visit. ECG interval measurements, including the QT interval, were obtained using three sequential QRS complexes, and averaged to produce a single ECG/QT interval for each ECG record. Heart rate correction was performed using the Fridericia and Bazett formulae. All the ECGs performed during the study were reviewed centrally by a cardiologist. An interim analysis of the ECG data was performed once the 10 patients in the extensive ECG monitoring cohort completed one cycle of therapy. If no more than one patient in this cohort had prolonged QTc > 500 msec, then subsequent patients would be monitored using the abbreviated ECG monitoring schedule. An inductively coupled plasma-mass spectrometry assay was used for the determination of arsenic levels, derived from darinaparsin, in human plasma by Covance Laboratories, Inc. After dilution with 0.005% Triton® X-100 in 0.1% nitric acid, the samples were analyzed without pre-digestion against matrix-matched standard solutions. Intensity as counts per second from arsenic, mass 75, were measured. Terbium, mass 159, was used as an internal standard. Results were calculated from the net intensity ratio of arsenic to internal standard and reported as concentration of darinaparsin in plasma. Patients underwent pre-treatment disease evaluation with physical examination, bone marrow examination (if indicated), and radiological studies. These imaging studies included at least computed tomography (CT) and 18F-flourodeoxyglucose positron emission tomography (PET) or combined PET/CT scanning where available. Repeat evaluation with the same modality was performed after every 8 weeks (i.e., every two cycles). Response was assessed by investigators at each site using the 1999 International Working Group (IWG) response criteria for malignant lymphoma [20]. The study size of 41 patients with hematologic cancers was initially calculated based on an optimal two-stage design [23]. In this population, we considered an ORR (CR + PR) of 20% to be promising and 5% to be futile. An interim analysis was planned after the first 13 patients were enrolled. If at least one response was observed, a further 28 patients would be enrolled. Among 41 patients, assuming that 37 would be evaluable, the therapy would be considered promising if at least 4 responses were observed. The probability of observing at least 4 responses out of 37 evaluable patients with a true response rate of 20% was 0.90 whereas this probability was 0.10 with a true response rate of 5%. The probability of stopping early was 0.07 with a true response rate of 20% and 0.9 with a true response rate of 5%. The two-stage 95% CI for 4 responses out of 37 evaluable patients was 4–25%. The pre-planned analysis was performed after enrollment of the first 13 patients (all with lymphoma), that revealed 3 (23%) objective responses, resulting in a protocol amendment to adjust the total accrual goal to 29 lymphoma patients. This was based on the assumption that at least one more response would be seen, and an observed response rate of 4 out of 29 would exclude a true response rate of 5% (the futility threshold as described above) with 90% certainty. All patients who received at least one dose of darinaparsin were included in the safety and efficacy analysis population. In addition to the protocol-specified endpoints of overall response rate, duration of response, time to progression, and progression-free survival, two exploratory endpoints—TTF and OS—were calculated as follows; TTF was defined as the duration in months from the date of the first dose of study drug until the date of documented progression, recurrence, death or removal from the study due to toxicity, whichever was sooner. OS was defined as the duration in months from the date of the first dose of study drug until the date of death from any cause. Patients known to be alive were censored at the time of last contact. TTF and OS were estimated by the Kaplan–Meier method with corresponding two-sided 95% CIs for survival proportions based on Greenwood's variance and the log-transform method [24]. The true response rate was estimated by the exact 95% CI. Additional Supporting Information may be found in the online version of this article. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Peter J. Hosein*, Michael D. Craig , Martin S. Tallman , Ralph V. Boccia§, Brian L. Hamilton¶, Jonathan J. Lewis¶, Izidore S. Lossos*, * Division of Hematology/Oncology, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida, Division of Hematology/Oncology, Department of Medicine, West Virginia University School of Medicine, Morgantown, West Virginia, Memorial Sloan Kettering Cancer Center, New York, New York, § Center for Cancer and Blood Disorders, Bethesda, Maryland, ¶ ZIOPHARM Oncology, Inc., Boston, Massachusetts.