Oral arsenic trioxide–based maintenance regimens for first complete remission of acute promyelocytic leukemia: a 10-year follow-up study

Acute promyelocytic leukemia: what is the new standard of care?

Acute promyelocytic leukemia (APL) is one of the most exciting stories of modern medicine. Once a disease that was highly lethal, the majority of patients are now cured with the advent of molecularly targeted therapy with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). In many patients, chemotherapy can be omitted completely, particularly in patients with low- or intermediate-risk disease (white blood cell count ≤ 10,000/μl). Recent data show overall survival exceeding 90% with ATRA and ATO-based induction and consolidation strategies. In the uncommon patient in whom relapse does occur, most can still be cured with ATO and autologous hematopoietic cell transplantation. Remaining challenges in APL management include the rapid identification and treatment of newly diagnosed patients to decrease the early death rate, optimizing treatment strategies in high-risk patients (white blood cell count>10,000/μl), and the role of maintenance therapy in lower risk patients.

Oral arsenic trioxide-based regimen as salvage treatment for relapsed or refractory mantle cell lymphoma

BACKGROUND

Mantle cell lymphoma (MCL) is aggressive, and relapsed/refractory disease has poor outcomes.

PATIENTS AND METHODS

Thirty-nine patients (men = 34, women = 5) at 64 (41-82) years of age with relapsed/refractory MCL, ineligible for high-dose chemotherapy and had received 2 (1-5) prior regimens, were treated with a continuous oral regimen, comprising oral arsenic trioxide (oral-As2O3), chlorambucil and ascorbic acid.

RESULTS

Overall response rate was 49% (complete response, CR = 28%; partial response, PR = 21%). Only grade 1/2 toxicities were observed (hematologic: 56%, hepatic: 8%). Response was maintained in 11 patients (CR = 8; PR = 3), after a median of 24 (2-108) months. Independent prognostic factors for response were increased lactate dehydrogenase (P = 0.04) and unfavorable MCL international prognostic index (P = 0.04). At a median follow-up of 21 (1-118) months, the median progression-free survival (PFS) was 16 months, and overall survival (OS) 38 months. Independent prognostic factors for PFS were female gender (P = 0.002), and Eastern Cooperative Oncology Group (ECOG) performance score of 2 (P = 0.009). Independent prognostic factors for OS were female gender (P < 0.001), ECOG performance score of 2 (P = 0.03), non-response (P < 0.001), and disease progression after initial response (P = 0.05).

CONCLUSION

An oral regimen of oral-As2O3, chlorambucil and ascorbic acid was active with minimal toxicity in relapsed/refractory MCL, achieving durable responses in ∼30% of cases.

Acute Promyelocytic Leukemia (APL): Comparison Between Children and Adults

The outcome of adults and children with Acute Promyelocytic Leukemia (APL) has dramatically changed since the introduction of all trans retinoic acid (ATRA) therapy. Based on the results of several multicenter trials, the current recommendations for the treatment of patients with APL include ATRA and anthracycline-based chemotherapy for the remission induction and consolidation, and ATRA combined with low-dose chemotherapy for maintenance. This has improved the prognosis of APL by increasing the complete remission (CR) rate, actually > 90%, decreasing the induction deaths and by reducing the relapse rate, leading to cure rates nowadays exceeding 80% considering both adults and children.1-9 More recently the combination of ATRA and arsenic trioxide (ATO) as induction and consolidation therapy has been shown to be at least not inferior and possibly superior to ATRA plus chemotherapy in adult patients with APL conventionally defined as non-high risk (Sanz score).10 Childhood APL has customarily been treated on adult protocols. Data from several trials have shown that the overall outcome in pediatric APL appears similar to that reported for the adult population; however, some clinical and therapeutic aspects differ in the two cohorts which require some important considerations and treatment adjustments.

Treatment of acute promyelocytic leukemia with arsenic trioxide: clinical results and open questions

Acute promyelocytic leukemia (APL) is a rare form of acute myeloid leukemia. The specific translocation t(15;17), which results in the fusion gene PML-RARA is the diagnostic and pathomechanistic hallmark of APL. By combination, treatment consisting of the differentiating agent all-trans retinoic acid (ATRA), which targets this molecular lesion, and cytotoxic chemotherapy, cure can be achieved in over 70% of patients. Recently, arsenic trioxide (ATO) has emerged to be the most active single agent in the treatment of APL. Previous studies employing ATO in relapse settings reported average complete remission rates of 85% and a mean overall survival of over 60%. In recent approaches installing ATO in first-line treatment, ATO-induced response rates comparable to previous combination regimen. The results of these newer studies indicate that the backbone of chemotherapy can be dramatically reduced or completely replaced by ATO and ATRA with similar or even better outcome.

Role of arsenic trioxide in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a unique subtype of acute myeloid leukemia that is characterized by distinct clinical, morphological, cytogenetic, and molecular abnormalities. It is associated with a striking risk of early hemorrhagic death due to disseminated intravascular coagulation and hyperfibrinolysis. The prognosis of APL has improved dramatically following the introduction of all-trans retinoic acid (ATRA) and its combination with anthracycline-based chemotherapy during induction and consolidation. Patients with high-risk APL, defined by a white cell count >10 × 10(9)/L at diagnosis, also appear to benefit from the addition of intermediate- or high-dose cytarabine during consolidation. Arsenic trioxide (ATO) has proved to be even more effective than ATRA as a single agent, and is now routinely used for the treatment of the 20%-30% of patients who manifest disease relapse after initial treatment with ATRA and chemotherapy. ATO has a toxicity profile that differs considerably from that of both ATRA and cytotoxic chemotherapy, and accordingly presents its own specific challenges during treatment. Optimizing a strategy for the incorporation of ATO into initial therapy is currently the focus of several cooperative group trials, with an emphasis on minimizing or even eradicating the use of chemotherapy. ATRA plus ATO without chemotherapy appears to be adequate during induction and consolidation for patients with standard-risk APL, but triple therapy that includes limited anthracycline or gemtuzumab ozogamicin (GO) during induction is required for high-risk APL. Uncertainty still exists regarding the minimum amount of chemotherapy and number of consolidation cycles necessary, the optimal scheduling of ATO, and the potential utility of oral ATO administration. Although prolonged oral maintenance therapy is usually included in most current APL treatment protocols, its value remains controversial, and the superior anti-leukemic efficacy of ATO-based therapy may facilitate its elimination in the future.

Meta-analysis of all-trans retinoic acid-linked arsenic trioxide treatment for acute promyelocytic leukemia

OBJECTIVES

To explore the combination therapy of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO, As2O3) on acute promyelocytic leukemia (APL).

METHODS

A meta-analysis of six studies was performed. Among 415 included cases, 165 cases were in the ATRA + ATO group, 129 cases in the ATRA-alone group, and 121 cases in the ATO-alone group. The complete remission (CR) rate and incidences of three groups were compared, respectively, between the therapies of ATRA + ATO with ATRA-alone, ATRA + ATO with ATO-alone, and ATRA with ATO.

RESULTS

The assessment results showed that ATRA + ATO therapy significantly improved the CR rate and decreased the incidences of cutaneous reaction compared with ATRA-alone (P < 0.05). However, incidence of liver injury was higher in the ATRA + ATO and ATO-alone groups than that in ATRA-alone group (P < 0.05). Difference in the complications between ATRA + ATO therapy and ATO-alone was not significant (P > 0.05).

CONCLUSIONS

In conclusion, we suggest low-dose ATRA and ATO combination therapy may be more effective for the treatment of APL.

Anticancer activity of small-molecule and nanoparticulate arsenic(III) complexes

Starting in ancient China and Greece, arsenic-containing compounds have been used in the treatment of disease for over 3000 years. They were used for a variety of diseases in the 20th century, including parasitic and sexually transmitted illnesses. A resurgence of interest in the therapeutic application of arsenicals has been driven by the discovery that low doses of a 1% aqueous solution of arsenic trioxide (i.e., arsenous acid) lead to complete remission of certain types of leukemia. Since Food and Drug Administration (FDA) approval of arsenic trioxide (As2O3) for treatment of acute promyelocytic leukemia in 2000, it has become a front-line therapy in this indication. There are currently over 100 active clinical trials involving inorganic arsenic or organoarsenic compounds registered with the FDA for the treatment of cancers. New generations of inorganic and organometallic arsenic compounds with enhanced activity or targeted cytotoxicity are being developed to overcome some of the shortcomings of arsenic therapeutics, namely, short plasma half-lives and a narrow therapeutic window.

Retinoic acid plus arsenic trioxide, the ultimate panacea for acute promyelocytic leukemia?

Rarely in the field of cancer treatment did we experience as many surprises as with acute promyelocytic leukemia (APL). Yet, the latest clinical trial reported by Lo-Coco et al in the New England Journal of Medicine is a practice-changing study, as it reports a very favorable outcome of virtually all enrolled low-intermediate risk patients with APL without any DNA-damaging chemotherapy. Although predicted from previous small pilot studies, these elegant and stringently controlled results open a new era in leukemia therapy.

Arsenic trioxide suppressed mantle cell lymphoma by downregulation of cyclin D1

Mantle cell lymphoma (MCL) is aggressive with poor prognosis. Due to t(11;14)(q13;q32), cyclin D1 is overexpressed. The in vitro activities of arsenic trioxide (As2O3) in MCL were investigated. In MCL lines Jeko-1 and Granta-519, As2O3 induced dose-dependent and time-dependent increases in apoptosis accompanied by cyclin D1 suppression. Downregulation of cyclin D1 resulted in decreased retinoblastoma protein phosphorylation, which led to repressed G1 progression to S/G2 phases. As2O3 did not affect cyclin D1 gene transcription. Instead, As2O3 activated glycogen synthase kinase-3beta (by tyrosine-216 phosphorylation) and IkappaB kinase alpha/beta (by serine-176/180 phosphorylation), both of which phosphorylated cyclin D1 at threonine-286, leading to its poly-ubiquitination and degradation in the proteasome. These observations were recapitulated partly in primary MCL samples obtained from patients refractory to conventional treatment. Our findings suggested that As2O3 might be clinically useful in MCL.

Pathways of arsenic uptake and efflux

Arsenic is the most prevalent environmental toxic substance and ranks first on the U.S. Environmental Protection Agency's Superfund List. Arsenic is a carcinogen and a causative agent of numerous human diseases. Paradoxically arsenic is used as a chemotherapeutic agent for treatment of acute promyelocytic leukemia. Inorganic arsenic has two biological important oxidation states: As(V) (arsenate) and As(III) (arsenite). Arsenic uptake is adventitious because the arsenate and arsenite are chemically similar to required nutrients. Arsenate resembles phosphate and is a competitive inhibitor of many phosphate-utilizing enzymes. Arsenate is taken up by phosphate transport systems. In contrast, at physiological pH, the form of arsenite is As(OH)(3), which resembles organic molecules such as glycerol. Consequently, arsenite is taken into cells by aquaglyceroporin channels. Arsenic efflux systems are found in nearly every organism and evolved to rid cells of this toxic metalloid. These efflux systems include members of the multidrug resistance protein family and the bacterial exchangers Acr3 and ArsB. ArsB can also be a subunit of the ArsAB As(III)-translocating ATPase, an ATP-driven efflux pump. The ArsD metallochaperone binds cytosolic As(III) and transfers it to the ArsA subunit of the efflux pump. Knowledge of the pathways and transporters for arsenic uptake and efflux is essential for understanding its toxicity and carcinogenicity and for rational design of cancer chemotherapeutic drugs.

Arsenic trioxide stabilizes accumulations of adeno-associated virus virions at the perinuclear region, increasing transduction in vitro and in vivo

Interactions with cellular stress pathways are central to the life cycle of many latent viruses. Here, we utilize adeno-associated virus (AAV) as a model to study these interactions, as previous studies have demonstrated that cellular stressors frequently increase transduction of recombinant AAV (rAAV) vectors and may even substitute for helper virus functions. Since several chemotherapeutic drugs are known to increase rAAV transduction, we investigated the effect of arsenic trioxide (As(2)O(3)), an FDA-approved chemotherapeutic agent with known effects on several other virus life cycles, on the transduction of rAAV. In vitro, As(2)O(3) caused a dose-dependent increase in rAAV2 transduction over a broad range of cell lines from various cell types and species (e.g., HEK-293, HeLa, HFF hTERT, C-12, and Cos-1). Mechanistically, As(2)O(3) treatment acted to prevent loss of virions from the perinuclear region, which correlated with increased cellular vector genome retention, and was distinguishable from proteasome inhibition. To extend our investigation of the cellular mechanism, we inhibited reactive oxygen species formation and determined that the As(2)O(3)-mediated increase in rAAV2 transduction was dependent upon production of reactive oxygen species. To further validate our in vitro data, we tested the effect of As(2)O(3) on rAAV transduction in vivo and determined that treatment initiated transgene expression as early as 2 days posttransduction and increased reporter expression by up to 10-fold. Moreover, the transduction of several other serotypes of rAAV was also enhanced in vivo, suggesting that As(2)O(3) affects a pathway used by several AAV serotypes. In summary, our data support a model wherein As(2)O(3) increases rAAV transduction both in vitro and in vivo and maintains perinuclear accumulations of capsids, facilitating productive nuclear trafficking.

Osteoblasts survive the arsenic trioxide treatment by activation of ATM-mediated pathway

Arsenic trioxide (ATO) is widely used in tumor treatment, but excessive arsenic exposure can have adverse effects. We recently found that, in primary osteoblasts, ATO produces oxidative stress and causes DNA tailing, but does not induce apoptosis. We further examined the signaling pathway by which osteoblasts survive ATO treatment, and found that they were arrested at G2/M phase of the cell cycle at 30h and overrode the G2/M boundary at 48h. After treatment for 30h, there was increased Cdc2 phosphorylation and expression of Wee1, a Cdc2 kinase, and expression of the cell cycle inhibitor, p21(waf1/cip1), which interacts with Cdc2. Furthermore, levels of the phosphatase Cdc25C, which activates Cdc2, were decreased, while the ratio of its phosphorylated/inactivated form to the total amount was increased. Moreover, phosphorylation/activation of the checkpoint kinases Chk1, Chk2 and p53 levels were increased, as were levels of activated ATM and γ-H2AX. The cell viability was decreased as an ATM inhibitor was added. Additionally, these effects of ATO on γ-H2AX, Chk1, Chk2, p53, and p21(waf1/cip1) were reduced by an ATM inhibitor. These findings suggest that G2/M phase arrest of osteoblasts is mediated by Chk1/Chk2 activation via an ATM-dependent pathway by which osteoblasts survive.

Sporopachydermia cereana fungaemia in refractory leukaemia presenting as breakthrough infection during micafungin therapy

The Sporopachydermia cereana species lives in decaying stems of cactus and is exceptionally rare as a human pathogen. A 57-year-old man with therapy-refractory acute promyelocytic leukaemia developed severe neutropaenia. After about 3 weeks of micafungin used as prophylaxis, he developed high fever, multiple pulmonary nodular infiltrates and a painful leg lesion. Blood culture yielded a yeast which was not identified by the Vitek 2 system. On ITS1-5.8S-ITS2 gene sequencing, the isolate was identified as S. cereana. Antifungal sensitivity by the Etest showed that the minimum inhibitory concentration for fluconazole was 0.75 μg/mL, and for anidulafungin, it was >32 μg/mL. He responded to liposomal amphotericin B but later died of Escherichia coli septicaemia. There were no cactus plants in the vicinity, suggesting that S. cereana might have alternative habitats.

Treatment breakthroughs for the management of acute myeloid leukemia

SUMMARY Although there has been substantial improvement in the survival of younger patients with acute myeloid leukemia (AML) since the 1970s, over the past two decades subsequent gains have been modest. Survival rates in older patients with AML remain dismal and have seen minimal change since the advent of modern induction chemotherapy. However, over the past decade, there has been a dramatic increase in the development of new therapies that have promising potential to further improve survival in both older and younger patients with AML. In this review, we will examine recent and ongoing breakthroughs in genetic discovery and gene profiling, intensification of induction chemotherapy, the development of novel agents, the management of older adults and allogeneic hematopoietic cell transplantation. We will also discuss exciting advances in the management of acute promyelocytic leukemia; a disease that is now imminently curable.

All-trans-retinoic acid, idarubicin, and IV arsenic trioxide as initial therapy in acute promyelocytic leukemia (APML4)

The treatment of acute promyelocytic leukemia has improved considerably after recognition of the effectiveness of all-trans-retinoic acid (ATRA), anthracycline-based chemotherapy, and arsenic trioxide (ATO). Here we report the use of all 3 agents in combination in an APML4 phase 2 protocol. For induction, ATO was superimposed on an ATRA and idarubicin backbone, with scheduling designed to exploit antileukemic synergy while minimizing cardiotoxicity and the severity of differentiation syndrome. Consolidation comprised 2 cycles of ATRA and ATO without chemotherapy, followed by 2 years of maintenance with ATRA, oral methotrexate, and 6-mercaptopurine. Of 124 evaluable patients, there were 4 (3.2%) early deaths, 118 (95%) hematologic complete remissions, and all 112 patients who commenced consolidation attained molecular complete remission. The 2-year rate for freedom from relapse is 97.5%, failure-free survival 88.1%, and overall survival 93.2%. These outcomes were not influenced by FLT3 mutation status, whereas failure-free survival was correlated with Sanz risk stratification (P[trend] = .03). Compared with our previously reported ATRA/idarubicin-based protocol (APML3), APML4 patients had statistically significantly improved freedom from relapse (P = .006) and failure-free survival (P = .01). In conclusion, the use of ATO in both induction and consolidation achieved excellent outcomes despite a substantial reduction in anthracycline exposure. This trial was registered at the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12605000070639.

"Boldness be my friend" (Shakespeare; Cymbeline)

Au et al report in this issue of Blood that oral arsenic trioxide (ATO) may be safely used in maintenance therapy in acute promyelocytic leukemia (APL). This is a major improvement in convenience given that intravenous (IV)ATO requires daily administration for weeks at a time. In addition, the oral formulation may be less toxic. The time seems right to carefully explore the introduction of oral ATO earlier in treatment of the disease.