ATREUS - Phase II Study on the Activity of Trabectedin in Patients With Malignant Pleural Mesothelioma (MPM)

There are no approved agents for second-line treatment of MPM in patients who failed first line pemetrexed plus platinum derivatives regimens. Chemotherapy options are limited and include gemcitabine, vinorelbine and other antifolate compounds. The role of second-line chemotherapy is therefore not yet established and second-line patient population is considered suitable for phase II studies with investigational agents.

Trabectedin is an originally natural marine product, now obtained by a semisynthetic process, that induces a delay in S phase progression and a blockade in G2 phase of the cell cycle by a mode of action that seems different from that of other DNA-damaging agents (see citations). Although the exact mechanism of action of trabectedin has not been fully elucidated yet, it appears to be unique compared to other anticancer agents (see citations). Trabectedin binds to N2 of guanines in the minor groove of DNA, causing a bending of the minor groove towards the major groove.

In the randomised clinical trials in metastatic leiomyosarcoma or liposarcoma and in recurrent platinum-sensitive ovarian cancer, trabectedin is infused at 1.5 mg/m2 as a 24-hour infusion or 1.3 mg/m2 as a 3 hour infusion every 3 weeks (see citations). Balancing efficacy with safety the short infusion is preferable in clinical practice.

In soft tissue sarcoma the response rate did not exceed 10%, however, trabectedin has been shown to provide disease control, with progression arrest rates exceeding 50% and progression-free survival rates exceeding 20% at 6 months. In pre-treated ovarian cancer the objective response rate was 30% with a median time to disease progression of 5.7 months.

Trabectedin has not been extensively employed in MPM, however in phase I studies, some objective response in heavily pre-treated mesothelioma patients was seen.

The present study is aimed at evaluating the activity of trabectedin in MPM patients not candidate for radical surgery. This option is of particular interest due to lack of valid therapeutic options.

Translational studies will be performed to identify factors predictive of the activity of trabectedin in MPM.

Inclusion criteria

• Histologically proven unresectable MPM. In order to make a reproducible diagnosis, in particular regarding biphasic MPM, histology must derive from transthoracic biopsies (at least 3 representative samples) or from videothoracoscopy (at least 5 representative samples)
• Age >18 years
• Performance status 0-1 (ECOG)
• Measurable disease (CT-PET) according to RECIST criteria modified for malignant pleural mesothelioma
• Not more than one previous chemotherapy course (consisting of pemetrexed plus platinum derivative), excluded adjuvant therapy if PFS < 12 months
• A minimum of 3 weeks since previous tumour directed therapy
• Recovery from toxic effects of previous therapies to NCI CTC AE Grade 0-1
• Patients who have received palliative radiation are eligible if <30% of bone marrow was irradiated and normal haematological function was completely regained
• Haematologic variables: haemoglobin ≥ 9 g/dL, Absolute neutrophil count (ANC) ≥ 1,500/μL and Platelet count ≥ 100,000/μL
• Serum creatinine ≤1.5 mg/dL or creatinine clearance ≥ 30 mL/min
• Creatinine phosphokinase (CPK) ≤ 2.5 ULN
• Hepatic function variables: Total bilirubin ≤ ULN, Total alkaline phosphatase ≤ 2.5 ULN or if > 2.5 ULN alkaline phosphatase liver fraction or GGT or 5' nucleotidase must be determined and ≤ ULN, AST (serum aspartate transaminase [SGOT]) and ALT (serum alaninetransaminase [SGPT]) must be ≤ 2.5 x ULN, Albumin ≥ 25 g/L
• Signed informed consent
• Adequate contraceptive methods for male patients whose partner is of childbearing age/potential, during the study and for three months after the end of treatment

Exclusion criteria

• - Radiotherapy with curative intent to thoracic wall (concomitant with or prior to chemotherapy)
• - Uncompensated diabetes mellitus or other condition absolutely contra-indicating dexamethasone (used as pre-medication)
• - Patients enrolled in other study with experimental drugs
• - Women of childbearing age/potential
• - Prior exposure to trabectedin
• - History of other malignancies (except basal cell carcinoma or cervical carcinoma in situ, adequately treated), unless in remission from 5 years or more and judged of negligible potential of relapse
• - Active viral hepatitis or chronic liver disease
• - Unstable cardiac condition, including congestive heart failure or angina pectoris, myocardial infarction within one year before enrolment, uncontrolled arterial hypertension or arrhythmias
• - Active major infection
• - Other serious concomitant illness
• - Brain / leptomeningeal involvement