The core concepts of core binding factor acute myeloid leukemia: Current considerations for prognosis and treatment

Core binding factor acute myeloid leukemia (CBF AML), defined by t(8;21) or inv(16), is a subset of favorable risk AML. Despite its association with a high complete remission rate after induction and relatively good prognosis overall compared with other subtypes of AML, relapse risk after induction chemotherapy remains high. Optimizing treatment planning to promote recurrence free survival and increase the likelihood of survival after relapse is imperative to improving outcomes. Recent areas of research have included evaluation of the role of gemtuzumab in induction and consolidation, the relative benefit of increased cycles of high dose cytarabine in consolidation, the utility of hypomethylating agents and kinase inhibitors, and the most appropriate timing of stem cell transplant. Surveillance with measurable residual disease testing is increasingly being utilized for monitoring disease in remission, and ongoing investigation seeks to determine how to use this tool for early identification of patients who would benefit from proceeding to transplant. In this review, we outline the current therapeutic approach from diagnosis to relapse while highlighting the active areas of investigation in each stage of treatment.

Can Immune Therapy Cure Acute Myeloid Leukemia?

OPINION STATEMENT

Although safe and effective immune therapies have been developed in several cancers, this has not been so in acute myeloid leukaemia (AML). Studies of antibodies to CD33, CD123 and CLL-1 report with unconvincing efficacy and substantial adverse events. Lacking AML-specific target antigens, these approaches using non-specific antigen targets often cause unacceptable bone marrow toxicity and off-target adverse events. Studies of AML incidence in persons with immune deficiency indicate little if any immune surveillance against AML. In contrast, data studies of recipients of haematopoietic cell transplants support an effective allogeneic anti-AML effect associated with graft-versus-host disease (GvHD) and possibly a specific graft-versus-leukaemia (GvL) effect. A special problem in the immune therapy of AML is few neo-antigens compared with solid cancers because of a relatively low mutation frequency. Studies of CAR-T-, CAR-NK-adaptor CAR-T- and allogeneic NK-cells are progressing as are approaches using synthetic biology. Presently, there are no convincing data of efficacy of immune therapy in AML.

Electrostatic anti-CD33-antibody-protamine nanocarriers as platform for a targeted treatment of acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is a fatal clonal hematopoietic malignancy, which results from the accumulation of several genetic aberrations in myeloid progenitor cells, with a worldwide 5-year survival prognosis of about 30%. Therefore, the development of more effective therapeutics with novel mode of action is urgently demanded. One common mutated gene in the AML is the DNA-methyltransferase DNMT3A whose function in the development and maintenance of AML is still unclear. To specifically target "undruggable" oncogenes, we initially invented an RNAi-based targeted therapy option that uses the internalization capacity of a colorectal cancer specific anti-EGFR-antibody bound to cationic protamine and the anionic siRNA. Here, we present a new experimental platform technology of molecular oncogene targeting in AML.

METHODS

Our AML-targeting system consists of an internalizing anti-CD33-antibody-protamine conjugate, which together with anionic molecules such as siRNA or ibrutinib-Cy3.5 and cationic free protamine spontaneously assembles into vesicular nanocarriers in aqueous solution. These nanocarriers were analyzed concerning their physical properties and relevant characteristics in vitro in cell lines and in vivo in xenograft tumor models and patient-derived xenograft leukemia models with the aim to prepare them for translation into clinical application.

RESULTS

The nanocarriers formed depend on a balanced electrostatic combination of the positively charged cationic protamine-conjugated anti-CD33 antibody, unbound cationic protamine and the anionic cargo. This nanocarrier transports its cargo safely into the AML target cells and has therapeutic activity against AML in vitro and in vivo. siRNAs directed specifically against two common mutated genes in the AML, the DNA-methyltransferase DNMT3A and FLT3-ITD lead to a reduction of clonal growth in vitro in AML cell lines and inhibit tumor growth in vivo in xenotransplanted cell lines. Moreover, oncogene knockdown of DNMT3A leads to increased survival of mice carrying leukemia patient-derived xenografts. Furthermore, an anionic derivative of the approved Bruton's kinase (BTK) inhibitor ibrutinib, ibrutinib-Cy3.5, is also transported by this nanocarrier into AML cells and decreases colony formation.

CONCLUSIONS

We report important results toward innovative personalized, targeted treatment options via electrostatic nanocarrier therapy in AML.

Is there an optimal adjunct therapy to traditional cytotoxic induction?

The traditional cytotoxic induction regimen for acute myeloid leukemia (AML) is seven days of standard-dose cytarabine and three days of an anthracycline antibiotic (such as daunorubicin or idarubicin), commonly known as "7 + 3." Many studies have been conducted to find an additional agent that might improve efficacy. Data from select studies has shown, in certain populations, benefit to adding cladribine, clofarabine and lomustine to a traditional backbone. For mutation-based chemotherapy regimens, midostaurin with 7 + 3 is the current standard of care for FLT3-mutant, younger AML patients. As we learn more about the synergism of molecular agents and traditional anti-cancer treatments, we can hopefully develop novel regimens without abandoning some of the benefits of these mutation agnostic historical therapies.

MDSC targeting with Gemtuzumab ozogamicin restores T cell immunity and immunotherapy against cancers

BACKGROUND

Targeting of MDSCs is a major clinical challenge in the era of immunotherapy. Antibodies which deplete MDSCs in murine models can reactivate T cell responses. In humans such approaches have not developed due to difficulties in identifying targets amenable to clinical translation.

METHODS

RNA-sequencing of M-MDSCs and G-MDSCs from cancer patients was undertaken. Flow cytometry and immunohistochemistry of blood and tumours determined MDSC CD33 expression. MDSCs were treated with Gemtuzumab ozogamicin and internalisation kinetics, and cell death mechanisms determined by flow cytometry, confocal microscopy and electron microscopy. Effects on T cell proliferation and CAR-T cell anti-tumour cytotoxicity were identified in the presence of Gemtuzumab ozogamicin.

FINDINGS

RNA-sequencing of human M-MDSCs and G-MDSCs identified transcriptomic differences, but that CD33 is a common surface marker. Flow cytometry indicated CD33 expression is higher on M-MDSCs, and CD33+ MDSCs are found in the blood and tumours regardless of cancer subtype. Treatment of human MDSCs leads to Gemtuzumab ozogamicin internalisation, increased p-ATM, and cell death; restoring T cell proliferation. Anti-GD2-/mesothelin-/EGFRvIII-CAR-T cell activity is enhanced in combination with the anti-MDSC effects of Gemtuzumab ozogamicin.

INTERPRETATION

The study identifies that M-MDSCs and G-MDSCs are transcriptomically different but CD33 is a therapeutic target on peripheral and infiltrating MDSCs across cancer subtypes. The immunotoxin Gemtuzumab ozogamicin can deplete MDSCs providing a translational approach to reactivate T cell and CAR-T cell responses against multiple cancers. In the rare conditions of HLH/MAS gemtuzumab ozogamicin provides a novel anti-myeloid strategy. FUND: This work was supported by Cancer Research UK, CCLG, Treating Children with Cancer, and the alumni and donors to the University of Birmingham.

[Diagnosis and treatment of acute myeloid leukemia : The updated 2018 Onkopedia Guideline]

In April 2018, an updated version of the previously published guidelines on acute myeloid leukemia (AML) from 2010 and 2017 was released. A revision was necessary because of two positive aspects: First, new data and insights on risk stratification and monitoring, and second, the clinical development and approval of new agents. The modified genetic risk classification allows a more precise distinction of different diagnostic groups and consequently a better matched post-remission treatment. The availability of new targeted drugs such as inhibitors turns genetic analyses from a mere prognostic tool into an instrument for treatment decisions. Several recently approved agents expand the treatment options for AML and raise hope for an improved prognosis and cure in the future.