Introduction

The incidence of melanoma is rapidly increasing, with almost 76,000 new cases expected in the US in 2016; it is the fifth most commonly diagnosed cancer in males and seventh in females [1]. Until 2011, there were no life-extending systemic therapies for patients diagnosed with metastatic disease, de novo or after treatment for locoregional disease. The median overall survival was less than 1 year, with similar outcomes with dacarbazine monotherapy or polychemotherapy and immunotherapy regimens [2]. The widespread use of BRAF/MEK and immune checkpoint inhibitors has increased the number of the patients living with metastatic melanoma beyond a year to more than 50%, and at least 30% are alive long-term and potentially cured [3].

REOLYSIN® (pelareorep), a Type 3 Dearing reovirus, is a naturally occurring oncolytic virus that can selectively infect and kill cells with an activated RAS pathway [4, 5]. This activation can be the effect of RAS mutations or activation of upstream kinases in the mitogen-activated protein kinase pathway (MAPK). Preferential killing of RAS-activated cells is mostly related to the inhibition of autophosphorylation of the double-stranded RNA-activated protein kinase (PKR) in these cells that allows viral replication to take place [5]. Melanoma cells are highly permissive to viral cytopathogenic effect in vitro and in vivo [6]; clinical studies of REOLYSIN® suggested some activity in melanoma as a single agent administered either locally or systemically [7, 8]. REOLYSIN® can also induce adaptive antitumor immunity [9, 10]. The limited clinical efficacy of REOLYSIN® as single agent has been linked to the development of neutralizing antibodies that can potentially decrease viral access to the tumor. Attenuation of antibody responses with cytotoxic or immunosuppressive agents in animal models has been demonstrated to enhance antitumor activity [11–13].

In 2009, we undertook a phase II trial of paclitaxel and carboplatin in combination with REOLYSIN®. Paclitaxel/carboplatin chemotherapy has shown activity in melanoma [14–16], and can attenuate neutralizing antibody responses, thus allowing higher viral penetration in the tumor [17]. Furthermore, REOLYSIN® has synergistic effects with platinum agents and taxanes [18, 19] and has been safely combined with paclitaxel and carboplatin in prior studies [17, 20, 21]. Herein, we report the final results of this phase II trial.

Materials and methods

Study design

REO 020 is a phase II, single-arm, open label study of REOLYSIN® administered in combination with paclitaxel and carboplatin in patients with metastatic melanoma, who experienced disease progression after one or more prior therapies or were deemed ineligible for the standard first-line therapy.

Patients were eligible for participation if they had histologically or cytologically confirmed melanoma, regardless of site of origin, and at least one measureable lesion by cross-sectional imaging or direct visualization of skin lesions. Other inclusion criteria included a performance status of at least 2 in the Eastern Cooperative Group scale (ECOG), a life expectancy of at least 3 months and adequate bone marrow, liver, and renal function [absolute neutrophil count (ANC) ≥1.5 × 109/L, Platelets ≥100 × 109/L without platelet transfusion, hemoglobin ≥9.0 g/dL with or without RBC transfusion, serum creatinine ≤1.5 × upper limit of normal (ULN), bilirubin ≤1.5 × ULN and aspartate transaminase/alanine transaminase (AST/ALT) ≤2.5 × ULN]. Key exclusion criteria included prior therapy with carboplatin and or paclitaxel, the presence of or history of metastatic disease to the brain, significant cardiac disease, including pre-existing arrhythmia, uncontrolled angina pectoris, myocardial infarction within 1 year prior to study entry, or grade 2 or higher compromised left ventricular ejection fraction. Patients on immunosuppressive therapy or with known HIV or active hepatitis B or C infection were also excluded. Any prior surgery or systemic therapy (cytotoxic chemotherapy, immunotherapy or hormonal therapy) should have occurred more than 28 days from study entry.

Study objectives

The primary objective was to assess the antitumor effect of the treatment regimen in the study population in terms of objective response rate, ORR [i.e., partial response (PR) and complete response (CR) to treatment]. Key secondary objectives were to assess progression-free survival (PFS) and overall survival (OS) for the treatment regimen, the disease control [CR + PR + stable disease (SD)] rate and duration, and the safety and tolerability of the treatment regimen in the study population.

Patients were assessed for response with the response evaluation criteria for solid tumors (RECIST) version 1.1. Evaluation of tumor status was conducted at baseline, at the end of week 6 on study and then every 6 weeks on study until disease progression, study termination, initiation of subsequent anticancer therapy, death, loss to follow-up, or withdrawal of consent.

Study treatment

Patients were treated on day 1 of each cycle with paclitaxel as a 3 h intravenous infusion at a dose of 200 mg/m2 , followed by carboplatin as a 30 min intravenous infusion at a dose of AUC 6 mg/mL/min calculated by the Calvert’s formula, and then followed by REOLYSIN® administered as a 1 h intravenous infusion at a dose of 3 × 1010 TCID50. On days 2 through 5, REOLYSIN® was administered alone using the same dose on day 1. Patients received standard premedication for paclitaxel treatment (corticosteroid, H1 and H2 antagonist) to prevent hypersensitivity reactions. The treatment cycles were repeated every 21 days for up to 8 cycles. If the patient derived benefit from therapy, treatment with paclitaxel/carboplatin and REOLYSIN® could continue for more than 8 cycles. Patients could continue REOLYSIN® alone at the same schedule indefinitely under this protocol, provided they have not experienced either progressive disease or unacceptable drug-related toxicity that does not respond to either supportive care or dose reduction.

Patients experiencing severe toxicity had their REOLYSIN®, paclitaxel and carboplatin treatments withheld until toxicity resolved to baseline or grade 1. Severe toxicity included in any cycle ANC <0.5 × 109/L lasting for >7 days, ANC <0.1 × 109/L lasting for >3 days, or ANC <0.5 × 10 9/L with fever (>100.5 °F or >38.1 °C), platelet count <25 × 109/L, grade ≥ 2 cardiotoxicity, persistent grade 2 neurotoxicity or any other drug-related non-hematological grade 3/4 toxicity, except grade 3 flu-like symptoms, diarrhea, nausea and vomiting which may require dose reduction if persistent and not clinically manageable. Upon resolution, REOLYSIN®, paclitaxel and carboplatin therapy could recommence at a lower dose level as presented in Supplement Table 1. Minor flu-like illness, diarrhea, nausea, or vomiting was managed with the standard supportive care.

Table 1 Demographics of patients enrolled in the study
Full size table

Statistical analysis and sample size calculation

The phase II trial used a Simon two-stage design. The null hypothesis was that the ORR is less than or equal to 0.10. The alternative hypothesis was that the ORR is greater than or equal to 0.25. With a type I error of 0.05 and 80% power, the estimated sample size was 24.66 and the probability of early termination for futility of 0.736. Therefore, with an initial accrual of 18 patients in the first stage, the trial would be terminated if 2 or fewer obtain an objective response. If the trial proceeds to the second stage, a total of 43 patients will be studied. For both stages combined, if the total number responding is less than or equal to 7, the therapy would be deemed inactive. For the secondary endpoints, the 6-month PFS and OS were estimated using the Kaplan–Meier method.

Results

Fourteen patients were enrolled in one center (CTRC at University of Texas Health Science Center San Antonio) between November 16th, 2009 and September 24th, 2012. The last patient completed the study in February 2014. The patient disposition is shown in Fig. 1. All patients discontinued the study therapy secondary to disease progression. Even though the study met the efficacy requirement for activation of the second stage (more than two patients attained an objective response to therapy), a decision was made to terminate the study given the advances in immunotherapy and molecularly targeted therapy for the treatment of melanoma.

Fig. 1
figure 1

Patient disposition for the study

Full size image

The baseline characteristics are shown in Table 1. Fifty-seven percent were female, 86% Caucasian/Non-Hispanic. The median number of metastatic sites was 3 (range 2–6), and the most common metastatic site was the lung. Patients had received a median of two prior systemic therapies, with progressive disease as the best response to the most recent therapy in 62.5% of the eight patients who had received systemic therapy for metastatic disease prior to study enrollment. The most common prior systemic treatments were INF-α and dacarbazine.

Treatment and efficacy

The median number of treatment cycles was 6 (range 2–20); two patients went on to receive more than 8 cycles of combination therapy, one patient continued on REOLYSIN® maintenance after cycle 8. Only one patient required a dose reduction of the paclitaxel and carboplatin for low neutrophil count. There was no reduction in the REOLYSIN® dose, but patients missed a median of one dose (range 0–6). Thirty-four cycles out of a total of 106 cycles delivered were delayed (32%); the range per patient was 0 to 15. Nineteen cycles (56%) were delayed for low neutrophil count (mostly grade 2–68%).

The study met its efficacy goal for the first stage with three partial responses (ORR was 21%, Table 2). No complete responses were noted. The disease control rate was 85%. The median PFS and OS were 5.2 and 10.9 months, respectively (Fig. 2). The 1-year OS rate was 43%.

Table 2 Overall response rate by RECIST 1.1 (N = 14)
Full size table
Fig. 2
figure 2

Graph with OS (median 10.9 months) and PFS (median 5.2 months) probabilities

Full size image

Safety

The adverse event profile was consistent with the prior experience of REOLYSIN® in combination with cytotoxic chemotherapy (Table 3) and was manageable with supportive care. REOLYSIN® did not appear to worsen any of the known chemotherapy-related adverse events. The most common toxicity (86% of the patients) was pyrexia and was mostly attributed to REOLYSIN®. There was one patient with grade 3 febrile neutropenia. Other potential serious adverse events included implanted device infection in two patients, staphylococcal infection in one patient, and spinal compression in one patient (all grade 3); however these were not related to REOLYSIN® or chemotherapy administration. There were no grade 4 adverse effects or death on study.

Table 3 Toxicity profile (>10% frequency) of chemo and REOLYSIN® in the study
Full size table

Discussion

Effective treatments for metastatic melanoma were rare before the advent of molecularly targeted agents and immunotherapy in 2011, with dacarbazine providing modest palliation and no real improvement in survival. The paclitaxel/carboplatin combination for the treatment of metastatic melanoma has been investigated in at least three small trials using different doses and schedules, with overall response rates ranging between 19 and 26%, clinical benefit rate of 45–67% and overall survival of 8–9 months [14–16].

REOLYSIN®, a Type 3 Dearing oncolytic reovirus, has in vitro and in vivo activity against melanoma, with a favorable adverse event profile that allows combination with other agents. Building on the antineoplastic activity of the paclitaxel/carboplatin combination, REOLYSIN® monotherapy, and evidence of synergy between chemotherapeutics and oncolytic viruses, in 2009, we designed a two-stage, phase II trial examining the efficacy of paclitaxel/carboplatin & REOLYSIN® combination strategy. Even though the results of the first stage did allow us to proceed with the second stage, the success of novel targeted therapies and immunotherapy in melanoma triggered the termination of the study. Our results confirm the safety of the combination and suggest improved efficacy as clinical benefit rate, PFS, and OS appear improved compared with historical controls (5.2 vs. 3 and 10.9 vs. 9 months, respectively) [14, 16].

Recently, IMLYGIC™ (T-VEC/Talimogene Laherparepvec), a genetically engineered Herpes Simplex Virus administered intratumorly, became the first oncolytic virus approved for use in the United States for patients with locally advanced or non-resectable melanoma. Its approval was based on a phase III study revealing improved efficacy compared to subcutaneous granulocyte–macrophage colony stimulating factor (GM-CSF) [22]. The combination of T-VEC with immune checkpoint inhibitors in melanoma has shown promising results in early phase I/II trials, with response rates ranging between 48 and 56%, time to response 4–5.6 months and PFS of 10.6 months; grade 3/4 treatment-related adverse events occurred in a third of the patients [23–25].

REOLYSIN® can induce an adaptive antitumor immunity [9, 10] and has shown in vitro and in vivo synergy with immune checkpoint inhibitors as well as BRAF and MEK inhibitors [26, 27]. Given the impressive early results of T-VEC with immunotherapy, as well as preclinical data, combination strategies of REOLYSIN® with immune checkpoint inhibitors deserve further study in the treatment of patients with metastatic melanoma, possibly combined with low doses of chemotherapy to increase viral penetration in the tumor. In summary, REOLYSIN® combined with paclitaxel and carboplatin is a safe and potentially efficacious therapy for patients with metastatic or unresectable melanoma.

Conclusion

The phase II, single-arm, open label study of REOLYSIN® in combination with carboplatin and paclitaxel was found safe for patients with advanced malignant melanoma. The study met its efficacy goal for the first stage with three partial responses (ORR was 21%) and the disease control rate was 85%. The median PFS and OS were 5.2 and 10.9 months, respectively, with a 1-year OS rate of 43%. Additional combination studies using REOLYSIN® with chemo/immunotherapy drugs may support more favorable outcomes for patients in this indication.