Clofarabine in the treatment of newly diagnosed acute myeloid leukemia in older adults

Acute Myeloid Leukemia Treatment in the Elderly: A Comprehensive Review of the Present and Future

BACKGROUND

Acute myeloid leukemia (AML) is a disease of the hematopoietic system that remains a therapeutic challenge despite advances in our understanding of the underlying cancer biology in the past decade. It is also an affliction of the elderly that predominantly affects patients over 60 years of age. Standard therapy involves intensive chemotherapy that is often difficult to tolerate in older populations. Fortunately, recent developments in molecular targeting have shown promising results in treating leukemia, paving the way for novel treatment strategies that are easier to tolerate.

SUMMARY

Venetoclax, a BCL-2 inhibitor, when combined with a hypomethylating agent, has proven to be a highly effective and well-tolerated drug and established itself as a new standard for treating AML in patients who are unfit for standard intensive therapy. Other targeted therapies include clinically proven and FDA-approved agents, such as IDH1/2 inhibitors, FLT3 inhibitors, and Gemtuzumab, as well as newer and more experimental drugs such as magrolimab, PI-kinase inhibitors, and T-cell engaging therapy. Some of the novel agents such as magrolimab and menin inhibitors are particularly promising, providing therapeutic options to a wider population of patients than ever before. Determining who will benefit from intense or novel low-intense therapy remains a challenge, and it requires careful assessment of individual patient's fitness and disease characteristics.

KEY MESSAGES

This article reviews past and current treatment strategies that harness various mechanisms of leukemia-targeting agents and introduces novel therapies on the horizon aimed at exploring therapeutic options for the elderly and unfit patient population. It also provides a strategy to select the best available therapy for elderly patients with both newly diagnosed and relapsed/refractory AML.

Ni-Catalyzed Cross-Coupling of 2-Iodoglycals and 2-Iodoribals with Grignard Reagents: A Route to 2-C-Glycosides and 2'-C-Nucleosides

The synthesis of 2-C-glycals and 2-C-ribals was achieved in good yields using a nickel-catalyzed cross-coupling between 2-iodoglycals and 2-iodoribal respectively and Grignard reagents. The prepared 2-C-glycals and ribals were then transformed into 2-C-2-deoxyglycosides, 2-C-diglycosides and 2'-C-2'-deoxynucleosides. The developed method was applied to the synthesis of a 2-chloroadenine 2'-deoxyribonucleoside - a structural analogue of cladribine (Mavenclad®, Leustatin®) and clofarabine (Clolar®, Evoltra®), two compounds used in the treatment of relapsing-remitting multiple sclerosis and hairy cell leukemia.

Outcomes of previously untreated elderly patients with AML: a propensity score-matched comparison of clofarabine vs. FLAG

The 5-year overall survival (OS) in patients ≥ 60 years old with acute myeloid leukemia (AML) remains < 10%. Clofarabine-based induction (CLO) provides an alternative to low-intensity therapy (LIT) and palliative care for this population, but supporting data are conflicted. Recently, our institution adopted the FLAG regimen (fludarabine, cytarabine, and granulocyte colony-stimulating factor) based on data reporting similar outcomes to CLO in elderly patients with AML unable to tolerate anthracycline-based induction. We retrospectively analyzed the efficacy and safety of patients ≥ 60 years old with AML treated with FLAG or CLO over the past 10 years. We performed a propensity score match that provided 32 patients in each group. Patients treated with FLAG had a higher CR/CRi rate (65.6 vs. 37.5%, P = 0.045) and OS (7.9 vs. 2.8 months, P = 0.085) compared to CLO. Furthermore, FLAG was better tolerated with significantly less grade 3/4 toxicities and a shorter duration of neutropenia (18.5 vs. 30 days, P = 0.002). Finally, we performed a cost analysis that estimated savings to be $30,000-45,000 per induction with FLAG. Our study supports the use of FLAG both financially and as an effective, well-tolerated high-dose treatment regimen for elderly patients with AML. No cases of cerebellar neurotoxicity occurred.

Efficacy of CLARA in recurrent/refractory acute myeloid leukaemia patients unresponsive to FLAG chemotherapy

We hereby report our multicentre, retrospective experience with CLARA in patients with fludarabine/cytarabine/G-CSF (FLAG) refractory AML. The study included all consecutive R/R AML patients, who received CLARA salvage during October 2010-October 2015 period. All patients were unresponsive to FLAG salvage chemotherapy regimen and did not undergo previous allo-HCT. A total of 40 patients were included. Following CLARA 5 (12.5%) patients experienced induction mortality and 10 (25%) patients achieved CR. 25 (62.5%) patients were unresponsive to CLARA. 7 (17.5%) out of 10 patients in CR received allo-HCT. Median overall survival of patients who achieved CR after CLARA was 24.5 months (8.5-54.5) and 3 months (2.5-5), in patients who underwent and didn't allo-HCT, respectively. Our results indicate that CLARA may be good alternative even in FLAG refractory AML patients and can be used as a bridge to allo-HCT, who have a suitable donor and able to tolerate the procedure.

Natural Products as a Vital Source for the Discovery of Cancer Chemotherapeutic and Chemopreventive Agents

Throughout history, natural products have played a dominant role in the treatment of human ailments. For example, the legendary discovery of penicillin transformed global existence. Presently, natural products comprise a large portion of current-day pharmaceutical agents, most notably in the area of cancer therapy. Examples include Taxol, vinblastine, and camptothecin. These structurally unique agents function by novel mechanisms of action; isolation from natural sources is the only plausible method that could have led to their discovery. In addition to terrestrial plants as sources for starting materials, the marine environment (e.g., ecteinascidin 743, halichondrin B, and dolastatins), microbes (e.g., bleomycin, doxorubicin, and staurosporin), and slime molds (e.g., epothilone B) have yielded remarkable cancer chemotherapeutic agents. Irrespective of these advances, cancer remains a leading cause of death worldwide. Undoubtedly, the prevention of human cancer is highly preferable to treatment. Cancer chemoprevention, the use of vaccines or pharmaceutical agents to inhibit, retard, or reverse the process of carcinogenesis, is another important approach for easing this formidable public health burden. Similar to cancer chemotherapeutic agents, natural products play an important role in this field. There are many examples, including dietary phytochemicals such as sulforaphane and phenethyl isothiocyanate (cruciferous vegetables) and resveratrol (grapes and grape products). Overall, natural product research is a powerful approach for discovering biologically active compounds with unique structures and mechanisms of action. Given the unfathomable diversity of nature, it is reasonable to suggest that chemical leads can be generated that are capable of interacting with most or possibly all therapeutic targets.

Clofarabine in the treatment of elderly patients with acute myeloid leukemia

BACKGROUND

Elderly patients with acute myeloid leukemia (AML) have a poor outcome because of co- morbidities, poor tolerance to intensive chemotherapy and inherently more resistant disease. Clofarabine is a second generation nucleoside analogue which has shown promising activity in elderly patients with AML. This study was conducted to review the outcome of treatment with clofarabine in a group of such patients.

METHODS

The records of 5 elderly patients who were diagnosed to have AML and treated with clofarabine over a 12 month period were reviewed retrospectively.

RESULTS

There were 2 female and 3 male patients with a median age of 68 years (range 65-82). At the time of treatment, 2 patients had newly diagnosed AML not considered suitable for intensive therapy, while 3 patients had partial or no response to conventional chemotherapy. The overall response rate was 100%, all patients achieving a complete remission. Induction and consolidation were well tolerated. All patients developed neutropenia with a median duration of 20 days (range 17-42). One patient developed hand and foot syndrome and a generalized rash but recovered. There was no mortality and all patients remained in remission after a median follow-up of 5.2 months (Range 3-10).

CONCLUSION

Clofarabine (alone or in combination) is active in elderly AML patients with an acceptable safety profile and should be considered a potential option in this group.

Effectiveness of primary anti-Aspergillus prophylaxis during remission induction chemotherapy of acute myeloid leukemia

Although antifungal prophylaxis is frequently administered to patients with acute myeloid leukemia (AML) during remission-induction chemotherapy (RIC), its impact on reducing invasive fungal infections (IFIs) outside clinical trials is rarely reported. We performed a retrospective observational study to identify risk factors for development of IFIs (definite or probable, using revised European Organization for Research and Treatment of Cancer [EORTC] criteria) and all-cause mortality in a cohort of 152 AML patients receiving RIC (2009 to 2011). We also compared rates of IFI and mortality in patients who received echinocandin versus anti-Aspergillus azole (voriconazole or posaconazole) prophylaxis during the first 120 days of RIC. In multivariate analysis, clofarabine-based RIC (hazard ratio [HR], 3.5; 95% confidence interval [CI], 1.5 to 8.3; P = 0.004) and echinocandin prophylaxis (HR, 4.6; 95% CI, 1.8 to 11.9; P = 0.002) were independently associated with higher rates of IFI rates during RIC. Subsequent analysis failed to identify any malignancy- or chemotherapy-related covariates linked to echinocandin prophylaxis that accounted for the higher rates of breakthrough IFI. Although the possibility of other confounding variables cannot be excluded, our findings suggest that echinocandin-based prophylaxis during RIC for AML may be associated with a higher risk of breakthrough IFI.

Decitabine in the treatment of acute myeloid leukemia in elderly patients

The majority of patients with acute myeloid leukemia (AML) are elderly and have a poor prognosis despite induction therapy. Decitabine, a DNA-hypomethylating agent that induces differentiation and apoptosis of leukemic cells, is a well-tolerated alternative to aggressive chemotherapy. It is currently FDA-approved for myelodysplastic syndrome, including patients with 20%–30% bone marrow blasts. Recent clinical attention has focused on evaluating decitabine as frontline therapy for untreated high-risk elderly AML patients. A large randomized international phase III study comparing decitabine to supportive care and cytarabine in elderly AML patients demonstrated significantly improved complete remission rates, but the survival difference did not reach significance. Due to this, decitabine did not achieve FDA approval for AML, but continues to be used off-label. Current research is focused on further defining subgroups of elderly AML patients who may derive greater benefit from decitabine therapy and combining it with other low-intensity active agents for AML.

Phase I study of clofarabine in adult patients with acute myeloid leukemia in Japan

OBJECTIVE

There are limited treatment options for relapsed/refractory acute myeloid leukemia patients or previously untreated elderly (≥60 years) patients with acute myeloid leukemia. In Phase II studies from the USA and Europe, single-agent clofarabine demonstrated activity and acceptable toxicity in elderly patients with previously untreated acute myeloid leukemia. This Phase I, multicenter study assessed the maximum-tolerated dose, safety, pharmacokinetics and efficacy of clofarabine in Japanese adults with acute myeloid leukemia.

METHODS

Intravenous clofarabine (20, 30 and 40 mg/m(2)/day) was administered for 5 days to Japanese adult patients with relapsed or refractory acute myeloid leukemia or elderly patients with newly diagnosed acute myeloid leukemia.

RESULTS

Fourteen patients, median age of 67.5 (59-72) years, were enrolled in this study. Eleven out of 14 patients had relapsed/refractory acute myeloid leukemia. Three patients received clofarabine at 20 mg/m(2), six at 30 mg/m(2) and five at 40 mg/m(2). Frequently reported treatment-related adverse events included thrombocytopenia (100%), anemia (93%), neutropenia (86%), nausea (86%), alanine aminotransferase increase (71%), headache (71%) and febrile neutropenia (57%). Three patients experienced reversible dose-limiting toxicities; two had increased alanine aminotransferase with 30 and 40 mg/m(2) and one had Grade 3 elevation of serum amylase with 40 mg/m(2). The maximum-tolerated dose was 30 mg/m(2)/day. Cmax and exposure area under the curve0-24h increased with increasing dose and were proportional to dose through the tested dose range. Among the 14 assessable patients, four (29%) achieved complete remission and two (14%) complete remission without platelet recovery. The overall remission rate was 43%.

CONCLUSIONS

These results demonstrate safety and preliminary, promising activity of clofarabine in Japanese patients with acute myeloid leukemia. Further investigation is warranted.

Clofarabine in the treatment of acute myeloid leukemia in older adults

OBJECTIVE

To review the literature evaluating the efficacy and tolerability of clofarabine as a single agent and in combination therapy for older patients with acute myeloid leukemia (AML).

METHOD

A literature search of the PubMed database (1996-April 2012) using the search terms clofarabine and acute myeloid leukemia was performed. All relevant English language articles were reviewed. Clinical trials with patients aged 50 years or older diagnosed with AML were included.

RESULTS

Two studies evaluating clofarabine as monotherapy and five studies evaluating clofarabine in combination with cytarabine were reviewed. Clofarabine demonstrated activity in older adults with AML. Response rates and median overall survival (OS) for patients receiving clofarabine were similar to those for patients receiving conventional induction chemotherapy. The induction mortality rate with clofarabine was lower than that seen with intensive chemotherapy. However, clofarabine was associated with a significant risk of severe complications including myelosuppression and sepsis.

CONCLUSION

Clofarabine is an active agent for the treatment of older patients with AML as a single agent or in combination therapy. Based on published data and side-effect profiles, clofarabine may be an appropriate alternative to intensive chemotherapy for older patients with AML, offering similar response rates to traditional 7+3 chemotherapy with potentially decreased induction mortality. The use of clofarabine in combination with newer agents including DNA methyltransferase inhibitors like decitabine is a promising approach for older patients who are not eligible for intensive chemotherapy. Additional randomized controlled trials are needed to directly compare the efficacy of clofarabine as a single agent and in combination therapy compared with intensive chemotherapy regimens.