The European Medicines Agency review of ofatumumab (Arzerra®) for the treatment of chronic lymphocytic leukemia in patients refractory to fludarabine and alemtuzumab: summary of the scientific assessment of the European medicines agency committee for medicinal products for human use

Double attack strategy for leukemia using a pre-targeting bispecific antibody (CD20 Ab-mPEG scFv) and actively attracting PEGylated liposomal doxorubicin to enhance anti-tumor activity

BACKGROUND

Tumor-targeted nanoparticles hold great promise as new tools for therapy of liquid cancers. Furthermore, the therapeutic efficacy of nanoparticles can be improved by enhancing the cancer cellular internalization.

METHODS

In this study, we developed a humanized bispecific antibody (BsAbs: CD20 Ab-mPEG scFv) which retains the clinical anti-CD20 whole antibody (Ofatumumab) and is fused with an anti-mPEG single chain antibody (scFv) that can target the systemic liquid tumor cells. This combination achieves the therapeutic function and simultaneously "grabs" Lipo-Dox® (PEGylated liposomal doxorubicin, PLD) to enhance the cellular internalization and anticancer activity of PLD.

RESULTS

We successfully constructed the CD20 Ab-mPEG scFv and proved that CD20 Ab-mPEG scFv can target CD20-expressing Raji cells and simultaneously grab PEGylated liposomal DiD increasing the internalization ability up to 60% in 24 h. We further showed that the combination of CD20 Ab-mPEG scFv and PLD successfully led to a ninefold increase in tumor cytotoxicity (LC₅₀: 0.38 nM) compared to the CD20 Ab-DNS scFv and PLD (lC₅₀: 3.45 nM) in vitro. Importantly, a combination of CD20 Ab-mPEG scFv and PLD had greater anti-liquid tumor efficacy (P = 0.0005) in Raji-bearing mice than CD20 Ab-DNS scFv and PLD.

CONCLUSION

Our results indicate that this "double-attack" strategy using CD20 Ab-mPEG scFv and PLD can retain the tumor targeting (first attack) and confer PLD tumor-selectivity (second attack) to enhance PLD internalization and improve therapeutic efficacy in liquid tumors.

The safety profile of monoclonal antibodies for chronic lymphocytic leukemia

INTRODUCTION

Monoclonal antibodies (MoAbs), non-chemotherapeutic agents targeting the antigens present on chronic lymphocytic leukemia (CLL) lymphocytes, are being implemented increasingly more often as treatment options. Areas covered: This article reviews the similarities and differences in the structure, mechanism of action, efficacy and safety profile of commercially-available MoAbs and prevents new agents potentially useful for CLL treatment. Publications in English before June 2016 were surveyed on the MEDLINE database for articles. Proceedings of the American Society of Hematology held during the last five years were also included. Expert opinion: MoAbs, especially those targeting CD20, are highly effective biological options for first-line and salvage treatment of CLL, particularly in chemoimmunotherapy, and possibly also as maintenance therapy. Treatment with MoAbs is associated with reduced risk of such adverse events as cytopenias, infections and secondary neoplasias and is generally well tolerated. Depending on antibody type, the most common adverse events are usually transient and limited to grade 1 and 2 infusion-related reactions. In addition to commercially available MoAbs, several other antibodies exist which are targeted against different antigens studied in the clinical trials.

An ultra-deep sequencing strategy to detect sub-clonal TP53 mutations in presentation chronic lymphocytic leukaemia cases using multiple polymerases

Chronic lymphocytic leukaemia (CLL) is the most common clonal B-cell disorder characterized by clonal diversity, a relapsing and remitting course, and in its aggressive forms remains largely incurable. Current front-line regimes include agents such as fludarabine, which act primarily via the DNA damage response pathway. Key to this is the transcription factor p53. Mutations in the TP53 gene, altering p53 functionality, are associated with genetic instability, and are present in aggressive CLL. Furthermore, the emergence of clonal TP53 mutations in relapsed CLL, refractory to DNA-damaging therapy, suggests that accurate detection of sub-clonal TP53 mutations prior to and during treatment may be indicative of early relapse. In this study, we describe a novel deep sequencing workflow using multiple polymerases to generate sequencing libraries (MuPol-Seq), facilitating accurate detection of TP53 mutations at a frequency as low as 0.3%, in presentation CLL cases tested. As these mutations were mostly clustered within the regions of TP53 encoding DNA-binding domains, essential for DNA contact and structural architecture, they are likely to be of prognostic relevance in disease progression. The workflow described here has the potential to be implemented routinely to identify rare mutations across a range of diseases.

Ofatumumab in the treatment of non-Hodgkin's lymphomas

INTRODUCTION

Ofatumumab is a second-generation humanized monoclonal antibody targeting CD20 registered for the treatment of patients with relapsing/refractory chronic lymphocytic leukemia. This review will describe the activity of ofatumumab in patients with CD20 B-cell lymphomas.

AREAS COVERED

A review of all manuscript published on ofatumumab activity in B-cell lymphomas is presented with conclusions on the future use of this antibody in these patients.

EXPERT OPINION

Ofatumumab activity is low in indolent or aggressive B-cell lymphomas. The future of this drug is challenged by new monoclonal antibodies and new targeted drugs.

Ofatumumab in poor-prognosis chronic lymphocytic leukemia: a phase IV, non-interventional, observational study from the European Research Initiative on Chronic Lymphocytic Leukemia

We report the largest retrospective, phase IV non-interventional, observational study of ofatumumab therapy in heavily pre-treated patients with poor-prognosis chronic lymphocytic leukemia. Total number of patients was 103; median age was 65 years (range 39-85). Median number of prior lines of therapy was 4 (range 1-13), including, in most cases, rituximab-, fludarabine- and alemtuzumab-based regimens; 13 patients had been allografted. Of 113 adverse events, 28 (29%) were considered to be directly related to ofatumumab. Grade 3-4 toxicities included neutropenia (10%), thrombocytopenia (5%), anemia (3%), pneumonia (17%), and fever (3%). Two heavily pre-treated patients developed progressive multifocal leukoencephalopathy. On an intention-to-treat analysis, the overall response rate was 22% (3 complete response, 1 incomplete complete response). Median progression-free and overall survival times were 5 and 11 months, respectively. This study confirms in a daily-life setting the feasibility and acceptable toxicity of ofatumumab treatment in advanced chronic lymphocytic leukemia. The complete response rate, however, was low. Therefore, treatment with ofatumumab should be moved to earlier phases of the disease. Ideally, this should be done in combination with other agents, as recently approved for ofatumumab plus chlorambucil as front-line treatment for patients unfit for fludarabine. This study is registered at clinicaltrials.gov identifier:01453062.

Ofatumumab in refractory chronic lymphocytic leukemia: experience through the French early access program

BACKGROUND

The Autorisation Temporaire d'Utilisation (ATU) is an early access program available in France for drugs aimed at treating severe diseases not yet covered by a marketing authorization, for patients without any other therapeutic option and who cannot be included in a clinical trial.

PATIENTS AND METHODS

This report presents the use of single-agent ofatumumab in 30 patients with advanced chronic lymphocytic leukemia (CLL) in the French ATU program.

RESULTS

These very-high-risk patients had received multiple previous treatments (median = 6), and most had disease that was fludarabine-refractory or alemtuzumab-refractory (or both) or was unsuitable for alemtuzumab treatment. In the intent-to-treat analysis, the overall response rate was 47% (4 of 30, complete response; 10 of 30, partial response). Of 13 patients with 17p deletion, 6 displayed response to ofatumumab, including 2 complete responses. Treatment was well tolerated, with 17 grade 3 or 4 adverse events; 4 cases of grade 3 or 4 infusion reactions were reported, with favorable immediate outcome. Among nonhematologic complications, infections were the most frequent.

CONCLUSION

The results confirm the efficacy and acceptable tolerability profile of ofatumumab as a single agent in severely ill patients with CLL. Attention should be paid to possible early infusion reactions to ofatumumab, as well as to the risk of infection.

Ofatumumab: a novel, fully human anti-CD20 monoclonal antibody for the treatment of chronic lymphocytic leukemia

Ofatumumab is a fully human, IgG anti-CD20 monoclonal antibody codeveloped by GlaxoSmithKline (Brentford, UK) and Genmab (Copenhagen, Denmark). In preclinical studies, ofatumumab exhibited more potent in vitro activity than rituximab against B-cell malignancies and prolonged survival in in vivo animal models compared with rituximab. Ofatumumab is clinically well tolerated with initial infusion reactions being the predominant associated toxicity. Ofatumumab has demonstrated efficacy in relapsed/refractory chronic lymphocytic leukemia (CLL) and has received regulatory approval in both Europe and the USA for treatment of fludarabine and alemtuzumab refractory disease. Single-agent ofatumumab has resulted in overall response rates of 42-51% in relapsed/refractory CLL and up to 80% when combined with chemotherapy. In de novo CLL, overall response rates of 77-78% have been achieved.

Targeting hedgehog signaling in myelofibrosis and other hematologic malignancies

Treatment of myelofibrosis (MF), a BCR-ABL-negative myeloproliferative neoplasm, is challenging. The only current potentially curative option, allogeneic hematopoietic stem cell transplant, is recommended for few patients. The remaining patients are treated with palliative therapies to manage MF-related anemia and splenomegaly. Identification of a mutation in the Janus kinase 2 (JAK2) gene (JAK2 V617F) in more than half of all patients with MF has prompted the discovery and clinical development of inhibitors that target JAK2. Although treatment with JAK2 inhibitors has been shown to improve symptom response and quality of life in patients with MF, these drugs do not alter the underlying disease; therefore, novel therapies are needed. The hedgehog (Hh) signaling pathway has been shown to play a role in normal hematopoiesis and in the tumorigenesis of hematologic malignancies. Moreover, inhibitors of the Hh pathway have been shown to inhibit growth and self-renewal capacity in preclinical models of MF. In a mouse model of MF, combined inhibition of the Hh and JAK pathways reduced JAK2 mutant allele burden, reduced bone marrow fibrosis, and reduced white blood cell and platelet counts. Preliminary clinical data also suggest that inhibition of the Hh pathway, alone or in combination with JAK2 inhibition, may enable disease modification in patients with MF. Future studies, including one combining the Hh pathway inhibitor sonidegib and the JAK2 inhibitor ruxolitinib, are underway in patients with MF and will inform whether this combination approach can lead to true disease modification.

New treatment options for chronic lymphocytic leukemia

INTRODUCTION

Chemoimmunotherapy is the gold standard of therapy for patients with advanced chronic lymphocytic leukemia (CLL), resulting in high and durable complete response rates. However, all patients eventually relapse and CLL remains incurable. Newer and more rationally developed compounds are needed to improve CLL therapy, particularly in cases of refractory disease.

AREAS COVERED

Following a literature search on PubMed using 'chronic', 'lymphocytic', 'treatment' and 'therapy' as keywords, results obtained with novel agents were critically analyzed. Abstracts presented during 2013 at ASH, EHA, ICML, IWCLL and ASCO meetings were also included in the search.

EXPERT OPINION

New monoclonal antibodies, lenalidomide, B-cell receptor-signal transduction inhibitors and pro-apoptotic molecules have shown efficacy in patients with relapsed or refractory disease. Hopefully, the combined use of these molecules in risk-adapted treatment strategies will improve the outcome of patients with CLL and pave the way for their long-term control.

Preclinical activity of the type II CD20 antibody GA101 (obinutuzumab) compared with rituximab and ofatumumab in vitro and in xenograft models

We report the first preclinical in vitro and in vivo comparison of GA101 (obinutuzumab), a novel glycoengineered type II CD20 monoclonal antibody, with rituximab and ofatumumab, the two currently approved type I CD20 antibodies. The three antibodies were compared in assays measuring direct cell death (AnnexinV/PI staining and time-lapse microscopy), complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), and internalization. The models used for the comparison of their activity in vivo were SU-DHL4 and RL xenografts. GA101 was found to be superior to rituximab and ofatumumab in the induction of direct cell death (independent of mechanical manipulation required for cell aggregate disruption formed by antibody treatment), whereas it was 10 to 1,000 times less potent in mediating CDC. GA101 showed superior activity to rituximab and ofatumumab in ADCC and whole-blood B-cell depletion assays, and was comparable with these two in ADCP. GA101 also showed slower internalization rate upon binding to CD20 than rituximab and ofatumumab. In vivo, GA101 induced a strong antitumor effect, including complete tumor remission in the SU-DHL4 model and overall superior efficacy compared with both rituximab and ofatumumab. When rituximab-pretreated animals were used, second-line treatment with GA101 was still able to control tumor progression, whereas tumors escaped rituximab treatment. Taken together, the preclinical data show that the glyoengineered type II CD20 antibody GA101 is differentiated from the two approved type I CD20 antibodies rituximab and ofatumumab by its overall preclinical activity, further supporting its clinical investigation.

False-positive immunogenicity responses are caused by CD20+ B cell membrane fragments in an anti-ofatumumab antibody bridging assay

An electrochemiluminescent (ECL) bridging assay to detect anti-ofatumumab antibodies (ADA) in human serum samples was developed and validated. Using this assay format, clinical samples were first screened to identify potential ADA positive samples, which were then further tested by adding excess drug, confirming the positive signals as drug specific. However, when the method was implemented into clinical studies for ADA testing, a high positive rate was observed in the pre-dose samples collected from patients with chronic lymphocytic leukemia (CLL). Since the positive signals were not associated with ofatumumab (Ofa) treatment, and diminished after treatment, it was suspected that matrix interference might be responsible, resulting in false-positive responses. We performed a series of experimental investigations to identify, characterize, minimize or eliminate the possible false-positive responses. One possible source was identified to be CD20 (the target of Ofa) present on cell membrane fragments (CMFs). The false-positive responses caused by CD20(+) CMFs could be reduced by solid-phase immunodepletion, ultracentrifugation, or inhibited by adding another anti-CD20 antibody (rituximab). As a consequence, the ADA method was modified to minimize the matrix interference caused by CD20(+) CMFs and, then, validated for sample testing.

Emerging monoclonal antibodies and related agents for the treatment of chronic lymphocytic leukemia

Monoclonal antibodies (mAbs) – rituximab, ofatumumab and alemtuzumab – have been approved for use in the therapy of chronic lymphocytic leukemia (CLL). Recently, a new generation of anti-CD20 mAbs has become available for preclinical studies and clinical trials. These antibodies were engineered to have augmented antitumor activity by increasing complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity and Fc-binding affinity for the low-affinity variants of the Fcγ receptor IIIa. The most promising mAb directed against CD20 is obinutuzumab (GA-101). mAbs directed against CD22, CD37 and CD40 have also shown some activity in CLL. In addition, small modular immunopharmaceuticals – TRU-015 (anti-CD20) and TRU-016 (anti-CD37) – that retain Fc-mediated effector functions have been developed and investigated in preclinical studies and clinical trials. Antibody–drug conjugates and recombinant immunotoxins are also being evaluated in lymphoid malignancies. Further studies will elucidate the role of these agents in the treatment of CLL.

Results of a phase 1 study of AME-133v (LY2469298), an Fc-engineered humanized monoclonal anti-CD20 antibody, in FcγRIIIa-genotyped patients with previously treated follicular lymphoma

PURPOSE

AME-133v is a humanized monoclonal antibody engineered to have increased affinity to CD20 and mediate antibody-dependent cell-mediated cytotoxicity (ADCC) better than rituximab. Safety, pharmacokinetics, and efficacy were assessed in a phase 1/2 trial in patients with previously treated follicular lymphoma (FL).

PATIENTS AND METHODS

AME-133v was characterized in vitro by ADCC and cell binding assays. A phase 1 study was conducted in which 23 previously treated patients with FL were assigned sequentially to one of five dose-escalation cohorts of AME-133v at 2, 7.5, 30, 100, or 375 mg/m(2) weekly × 4 doses.

RESULTS

AME-133v showed a 13- to 20-fold greater binding affinity for CD20 and was 5- to 7-fold more potent than rituximab in ADCC assays. Cell binding assays showed AME-133v and rituximab competed for an overlapping epitope on the CD20 antigen, and AME-133v inhibited binding of biotinylated rituximab to CD20 in a concentration-dependent manner. AME-133v was well tolerated by patients and common related adverse events included chills and fatigue. One patient experienced a dose-limiting toxicity of neutropenia. AME-133v showed nonlinear pharmocokinetics with properties similar to rituximab. Selective reduction of B cells during and after AME-133v treatment was shown by flow cytometry of peripheral blood. A partial or complete response was observed in 5 of 23 (22%) patients and the median progression-free survival was 25.4 weeks.

CONCLUSIONS

AME-133v was safe and well tolerated at the doses tested. AME-133v showed encouraging results as an anti-CD20 therapy in heavily pretreated FL patients with the less favorable FcγRIIIa F-carrier genotype.