Four Drug Reinduction With Bortezomib for Relapsed or Refractory ALL or LL in Children and Young Adults

1.0 GOALS AND OBJECTIVES (SCIENTIFIC AIMS)

1.1 Primary Aims

1.1.1 To evaluate the feasibility and toxicity of using bortezomib in combination with the ALL R3 re-induction regimen in pediatric patients with relapsed or refractory ALL or LL.

1.1.2 To determine the rate of complete response and negative minimal residual disease status following bortezomib combined with R3 reinduction.

2.0 BACKGROUND

Despite the progress that has been made in the treatment of ALL in children, relapse of disease remains a significant treatment problem. By itself, the number of patients with relapsed ALL would be the 4th most common childhood malignancy and overall survival in these patients is poor. Using conventional treatments, second remission rates after bone marrow relapse in ALL are 81-93% and long-term event free survival (EFS) is only 27-50%. Initial standard therapy for children following relapse includes a four drug reinduction strategy, typically using prednisone, vincristine, PEG-asparaginase, and doxorubicin. For children with first marrow relapse of ALL less than 36 months from diagnosis, this four drug reinduction strategy results in a CR rate of 68%. However, 75% of patients in CR2 had minimal residual disease (MRD) that was positive (>0.01%) at the end of reinduction. The presence of MRD in relapsed ALL is strongly associated with worse long term outcomes. For children with ALL that relapsed following a second (CR2) remission, outcomes are dismal with 5 year disease free survival of 15%.

In 2010, results were published of the ALL R3 trial from the Children's Cancer and Leukemia Group in the United Kingdom and Ireland. This trial randomized children with first relapse of ALL to receive a four drug reinduction using either mitoxantrone or idarubicin as the anthracycline. The study was closed early due to a statistically significant improvement in survival for children randomized to mitoxantrone. Children who received mitoxantrone had a 3 year disease free survival of 64.6% compared to 35.9% in the idarubicin group. Toxicities in this study were not excessive, and children randomized to receive mitoxantrone had significantly less toxicity than those in the idarubicin group. Based on the results of this trial, the Children's Oncology Group (COG) has begun using this reinduction regimen as the backbone for new clinical trials for children with relapsed ALL.

Despite the improvement in outcomes for the children with relapsed ALL treated with mitoxantrone on the R3 study, there is still a need for continued efforts to improve outcomes in patients with ALL and LL that experience a relapse. This is particularly true for high risk groups such as those who have an early bone marrow relapse (<36 months from diagnosis), second or greater relapse or relapsed LL where long term survival remains less than 50% Bortezomib is a proteasome inhibitor that has demonstrated activity in a number of cancer types including acute leukemias. Bortezomib acts by inhibiting the ubiquitin-proteasome pathway resulting in the blockade of NF-κB activation and the stabilization of multiple proapoptotic proteins including p53, p21, p27, and Bax. Collectively, these effects induce apoptosis and enhance the cytotoxic effects of chemotherapy. In the Pediatric Preclinical Testing Program (PPTP), bortezomib showed activity against a number of ALL cell lines. As a single agent, bortezomib was effective at inhibiting NF-κB but there was no clinical response in 9 heavily pretreated children with ALL. Proteasome inhibition is able to induce apoptosis, and may be best utilized in combination with other conventional chemotherapy drugs to help overcome resistance. Preclinical evaluation of bortezomib with a number of drugs commonly used in pediatric ALL therapy demonstrated synergy with dexamethasone and additive effects when given along with vincristine, asparaginase, and doxorubicin.

In a phase 1 study of children with relapsed ALL of bortezomib combined with a four drug reinduction using dexamethasone, vincristine, doxorubicin, PEG-asparaginase and intrathecal therapy, bortezomib at a dose of 1.3 mg/m2 given on days 1, 4, 8 and 11 was well tolerated. The phase 2 study of this regimen was able to produce a complete response or complete response without platelet recovery in 73% of patients. These results are encouraging as these were heavily pretreated patients treated with 2 or 3 previous regimens. Due to 3 deaths from infectious toxicities, the study was amended to require infectious prophylaxis with vancomycin, levofloxacin, and voriconazole. No further deaths were seen in children following this change. Other toxicities seen on this study include grade 3 peripheral neuropathy in 2 patients.

This is a phase II study designed to investigate the combination of bortezomib with the mitoxantrone reinduction regimen used in the ALL R3 trial. The study will enroll patients with high risk ALL relapse including early bone marrow relapse and second or greater relapse of any kind. Patients with relapsed LL will also be eligible. Bone marrow evaluation will be performed after blood counts recover to assess the rate of CR (<5% bone marrow blasts) and MRD status in children following this regimen. Further treatment with or without HSCT will be at the discretion of the primary physician.

2.1 Bortezomib for Injection 2.1.1 Scientific Background Bortezomib for Injection is a small-molecule proteasome inhibitor developed by Millennium Pharmaceuticals, Inc., (Millennium) as a novel agent to treat human malignancies. Bortezomib is currently approved by the United States Food and Drug Administration (US FDA) for the treatment of patients with multiple myeloma (MM). It is also indicated for the treatment of patients with mantle cell lymphoma (MCL) who have received at least 1 prior therapy. In the European Union (EU), bortezomib in combination with melphalan and prednisone is indicated for the treatment of patients with previously untreated MM who are not eligible for high-dose chemotherapy with bone marrow transplant. Bortezomib is indicated as monotherapy for the treatment of progressive MM in patients who have received at least 1 prior therapy and who have already undergone or are unsuitable for bone marrow transplantation.

By inhibiting a single molecular target, the proteasome, bortezomib affects multiple signaling pathways. The antineoplastic effect of bortezomib likely involves several distinct mechanisms, including inhibition of cell growth and survival pathways, induction of apoptosis, and inhibition of expression of genes that control cellular adhesion, migration, and angiogenesis. Thus, the mechanisms by which bortezomib elicits its antitumor activity may vary among tumor types, and the extent to which each affected pathway is critical to the inhibition of tumor growth could also differ. Bortezomib has a novel pattern of cytotoxicity in National Cancer Institute (NCI) in vitro and in vivo assays.(19) In addition, bortezomib has cytotoxic activity in a variety of xenograft tumor models, both as a single agent and in combination with chemotherapy and radiation. Notably, bortezomib induces apoptosis in cells that over express bcl-2, a genetic trait that confers unregulated growth and resistance to conventional chemotherapeutics.

The mechanisms of action leading up to apoptosis have been more clearly defined and include initiation of the unfolded protein response and direct/indirect effects on various molecular targets including cell cycle control proteins p27 and p21, cyclins, signal transduction molecules, transcription factors c-jun and HIF1-, tumor suppressor protein p53, angiogenesis factors, and many others. Bortezomib is thought to be efficacious in multiple myeloma via its inhibition of nuclear factor B (NF-B) activation, its attenuation of interleukin-6 (IL-6)-mediated cell growth, a direct apoptotic effect, and possibly anti-angiogenic and other effects.