Arsenic trioxide Other names: Arsenic Sesquioxide Arsenic Oxidearsenous Trioxide

QT/QTc prolongation is expected during treatment with arsenic trioxide, and torsade de pointes and complete heart block have been reported. Patients who are receiving, or who have received, medicinal products known to cause hypokalaemia or hypomagnesaemia, such as diuretics or amphotericin B, may be at higher risk for torsade de pointes. Caution is advised when arsenic trioxide is co-administered with other medicinal products known to cause QT/QTc interval prolongation such as macrolide antibiotics, the antipsychotic thioridazine, or medicinal products known to cause hypokalaemia or hypomagnesaemia.

Since no data are available across all hepatic impairment groups and hepatotoxic effects may occur during the treatment with arsenic trioxide, caution is advised in the use of arsenic trioxide in patients with hepatic impairment.

Since no data are available across all renal impairment groups, caution is advised in the use of arsenic trioxide in patients with renal impairment.

Treatment with arsenic trioxide has been associated with the development of hyperleucocytosis (≥10 × 10³/μl) in some relapsed/refractory APL patients. There did not appear to be a relationship between baseline white blood cell (WBC) counts and development of hyperleucocytosis nor did there appear to be a correlation between baseline WBC count and peak WBC counts. Hyperleucocytosis was never treated with additional chemotherapy and resolved on continuation of TRISENOX. WBC counts during consolidation were not as high as during induction treatment and were <10 × 10³/μl, except in one patient who had a WBC count of 22 × 10³/μl during consolidation. Twenty relapsed/refractory APL patients (50%) experienced leucocytosis; however, in all these patients, the WBC count was declining or had normalized by the time of bone marrow remission and cytotoxic chemotherapy or leucopheresis was not required. In newly diagnosed patients with low to intermediate risk APL leucocytosis developed during induction therapy in 35 of 74 (47%) patients. However all cases were successfully managed with hydroxyurea therapy.

In newly diagnosed and relapsed/refractory APL patients who develop sustained leucocytosis after initiation of therapy, hydroxyurea should be administered. Hydroxyurea should be continued at a given dose to keep the white blood cell count ≤10 × 10³/μl and subsequently tapered.

Table 1. Recommendation for initiation of hydroxyurea:

Arsenic trioxide can cause QT interval prolongation and complete atrioventricular block. QT prolongation can lead to a torsade de pointes-type ventricular arrhythmia, which can be fatal. Previous treatment with anthracyclines may increase the risk of QT prolongation. The risk of torsade de pointes is related to the extent of QT prolongation, concomitant administration of QT prolonging medicinal products (such as class Ia and III antiarrythmics (e.g. quinidine, amiodarone, sotalol, dofetilide), antipsychotics (e.g. thioridazine), antidepressants (e.g. amitriptyline), some macrolides (e.g. erythromycin), some antihistamines (e.g. terfenadine and astemizole), some quinolone antibiotics (e.g. sparfloxacin), and other individual medicinal products known to increase QT interval (e.g. cisapride)), a history of torsade de pointes, pre-existing QT interval prolongation, congestive heart failure, administration of potassium-wasting diuretics, amphotericin B or other conditions that result in hypokalaemia or hypomagnesaemia.

In clinical trials, in the relapsed/refractory setting, 40% of patients treated with arsenic trioxide experienced at least one QT corrected (QTc) interval prolongation greater than 500 msec. Prolongation of the QTc was observed between 1 and 5 weeks after arsenic trioxide infusion, and then returned to baseline by the end of 8 weeks after arsenic trioxide infusion. One patient (receiving multiple, concomitant medicinal products, including amphotericin B) had asymptomatic torsade de pointes during induction therapy for relapsed APL with arsenic trioxide. In newly diagnosed APL patients 15.6% showed QTc prolongation with arsenic trioxide in combination with ATRA. In one newly diagnosed patient induction treatment was terminated because of severe prolongation of the QTc interval and electrolyte abnormalities on day 3 of induction treatment.

ECG and electrolyte monitoring recommendations

Prior to initiating therapy with arsenic trioxide, a 12-lead ECG must be performed and serum electrolytes (potassium, calcium, and magnesium) and creatinine must be assessed; pre-existing electrolyte abnormalities must be corrected and, if possible, medicinal products that are known to prolong the QT interval must be discontinued. Patients with risk factors of QTc prolongation or risk factors of torsade de pointes should be monitored with continuous cardiac monitoring (ECG). For QTc greater than 500 msec, corrective measures must be completed and the QTc reassessed with serial ECGs and, if available, a specialist advice could be sought prior to considering using arsenic trioxide. During therapy with arsenic trioxide, potassium concentrations must be kept above 4 mEq/l and magnesium concentrations must be kept above 1.8 mg/dl. Patients who reach an absolute QT interval value >500 msec must be reassessed and immediate action must be taken to correct concomitant risk factors, if any, while the risk/benefit of continuing versus suspending arsenic trioxide therapy must be considered.

If syncope, rapid or irregular heartbeat develops, the patient must be hospitalised and monitored continuously, serum electrolytes must be assessed, arsenic trioxide therapy must be temporarily discontinued until the QTc interval regresses to below 460 msec, electrolyte abnormalities are corrected, and the syncope and irregular heartbeat cease. After recovery, treatment should be resumed at 50% of the preceding daily dose. If QTc prolongation does not recur within 7 days of restarting treatment at the reduced dose, treatment with arsenic trioxide can be resumed at 0.11 mg/kg body weight per day for a second week. The daily dose can be escalated back to 100% of the original dose if no prolongation occurs. There are no data on the effect of arsenic trioxide on the QTc interval during the infusion. Electrocardiograms must be obtained twice weekly, and more frequently for clinically unstable patients, during induction and consolidation.

Cases of encephalopathy were reported with treatment with arsenic trioxide. Wernicke encephalopathy after arsenic trioxide treatment was reported in patients with vitamin B₁ deficiency. Patients at risk of B₁ deficiency should be closely monitored for signs and symptoms of encephalopathy after arsenic trioxide initiation. Some cases recovered with vitamin B₁ supplementation.

In newly diagnosed patients with low to intermediate risk APL 63.2% developed grade 3 or 4 hepatic toxic effects during induction or consolidation treatment with arsenic trioxide in combination with ATRA. However, toxic effects resolved with temporary discontinuation of either arsenic trioxide, ATRA or both. Treatment with arsenic trioxide must be discontinued before the scheduled end of therapy at any time that a hepatotoxicity grade 3 or greater on the National Cancer Institute Common Toxicity Criteria is observed. As soon as bilirubin and/or SGOT and/or alkaline phosphatase are decreased to below 4 times the normal upper level, treatment with arsenic trioxide should be resumed at 50% of the previous dose during the first 7 days. Thereafter, in absence of worsening of the previous toxicity, arsenic trioxide should be resumed at full dosage. In case of reappearance of hepatotoxicity, arsenic trioxide must be permanently discontinued.

27% of patients with APL, in the relapsed/refractory setting, treated with arsenic trioxide have experienced symptoms similar to a syndrome called the retinoic-acid-acute promyelocytic leukaemia (RA-APL) or APL differentiation syndrome, characterised by fever, dyspnoea, weight gain, pulmonary infiltrates and pleural or pericardial effusions, with or without leucocytosis. This syndrome can be fatal.

In newly diagnosed APL patients treated with arsenic trioxide and all-trans-retinoic acid (ATRA), APL differentiation syndrome was observed in 19% including 5 severe cases. At the first signs that could suggest the syndrome (unexplained fever, dyspnoea and/or weight gain, abnormal chest auscultatory findings or radiographic abnormalities), treatment with arsenic trioxide must be temporarily discontinued and high-dose steroids (dexamethasone 10 mg intravenously twice a day) must be immediately initiated, irrespective of the leukocyte count and continued for at least 3 days or longer until signs and symptoms have abated. If clinically justified/required, concomitant diuretic therapy is also recommended.

The majority of patients do not require permanent termination of arsenic trioxide therapy during treatment of the APL differentiation syndrome. As soon as signs and symptoms have subsided, treatment with arsenic trioxide can be resumed at 50% of the previous dose during the first 7 days. Thereafter, in the absence of worsening of the previous toxicity, arsenic trioxide might be resumed at full dosage. In the case of the reappearance of symptoms arsenic trioxide should be reduced to the previous dosage. In order to prevent the development of the APL differentiation syndrome during induction treatment, prednisone (0.5 mg/kg body weight per day throughout induction treatment) may be administered from day 1 of arsenic trioxide application to the end of induction therapy in APL patients.

It is recommended that chemotherapy not be added to treatment with steroids since there is no experience with administration of both steroids and chemotherapy during treatment of the leukocyte activation syndrome due to arsenic trioxide. Post-marketing experience suggests that a similar syndrome may occur in patients with other types of malignancy. Monitoring and management for these patients should be as described above.

Arsenic trioxide has been shown to be embryotoxic and teratogenic in animal studies. There are no studies in pregnant women using arsenic trioxide. If this medicinal product is used during pregnancy or if the patient becomes pregnant while taking this product, the patient must be informed of the potential harm to the foetus.

Arsenic is excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from arsenic trioxide, breastfeeding must be discontinued prior to and throughout administration.

Contraception in males and females

Women of childbearing potential and men must use effective contraception during treatment with arsenic trioxide.

Fertility

No clinical or non-clinical fertility studies have been conducted with arsenic trioxide.

Arsenic trioxide has no or negligible influence on the ability to drive and use machines.

Summary of the safety profile

Related adverse reactions of CTC grade 3 and 4 occurred in 37% of relapsed/refractory APL patients in clinical trials. The most commonly reported reactions were hyperglycaemia, hypokalaemia, neutropenia, and increased alanine amino transferase (ALT). Leucocytosis occurred in 50% of patients with relapsed/refractory APL, as determined by haematology assessments.

Serious adverse reactions were common (1-10%) and not unexpected in the relapsed/refractory population. Those serious adverse reactions attributed to arsenic trioxide included APL differentiation syndrome (3), leucocytosis (3), prolonged QT interval (4, 1 with torsade de pointes), atrial fibrillation/atrial flutter (1), hyperglycaemia (2) and a variety of serious adverse reactions related to haemorrhage, infections, pain, diarrhoea, nausea.

In general, treatment-emergent adverse events tended to decrease over time, in relapsed/refractory APL patients perhaps accounted for by amelioration of the underlying disease process. Patients tended to tolerate consolidation and maintenance treatment with less toxicity than in induction. This is probably due to the confounding of adverse events by the uncontrolled disease process early on in the treatment course and the myriad concomitant medicinal products required to control symptoms and morbidity.

In a phase 3, multicentre, non-inferiority trial comparing all-trans-retinoic acid (ATRA) plus chemotherapy with ATRA plus arsenic trioxide in newly diagnosed low-to-intermediate risk APL patients (Study APL0406), serious adverse reactions including hepatic toxicity, thrombocytopenia, neutropenia and QTc prolongation were observed in patients treated with arsenic trioxide.

Tabulated list of adverse reactions

The following undesirable effects have been reported in the APL0406 study in newly diagnosed patients and in clinical trials and/or post-marketing experience in relapsed/refractory APL patients. Undesirable effects are listed in the table below as MedDRA preferred term by system organ class and frequencies observed during arsenic trioxide clinical trials in 52 patients with refractory/relapsed APL. Frequencies are defined as: (very common ≥1/10), (common ≥1/100 to <1/10), (uncommon ≥1/1,000 to <1/100), not known (cannot be estimated from available data).

Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.

* In the CALGB study C9710, 2 cases of grade ≥3 increased GGT were reported out of the 200 patients who received arsenic trioxide consolidation cycles (cycle 1 and cycle 2) versus none in the control arm.

Description of selected adverse reactions

Differentiation syndrome

During arsenic trioxide treatment, 14 of the 52 patients in the APL studies in the relapsed setting had one or more symptoms of APL differentiation syndrome, characterised by fever, dyspnoea, weight gain, pulmonary infiltrates and pleural or pericardial effusions, with or without leucocytosis. Twenty-seven patients had leucocytosis (WBC ≥10 × 10³/l) during induction, 4 of whom had values above 100,000/l. Baseline white blood cell (WBC) counts did not correlate with development of leucocytosis on study, and WBC counts during consolidation therapy were not as high as during induction. In these studies, leucocytosis was not treated with chemotherapeutic medicinal products. Medicinal products that are used to lower the white blood cell count often exacerbate the toxicities associated with leucocytosis, and no standard approach has proven effective. One patient treated under a compassionate use program died from cerebral infarct due to leucocytosis, following treatment with chemotherapeutic medicinal products to lower WBC count. Observation is the recommended approach with intervention only in selected cases.

Mortality in the pivotal studies in the relapsed setting from disseminated intravascular coagulation (DIC) associated haemorrhage was very common (>10%), which is consistent with the early mortality reported in the literature.

In newly diagnosed patients with low to intermediate risk APL, differentiation syndrome was observed in 19% including 5 severe cases.

In post marketing experience, a differentiation syndrome, like retinoic acid syndrome, has also been reported for the treatment of malignancies other than APL with arsenic trioxide.

QT interval prolongation

Arsenic trioxide can cause QT interval prolongation. QT prolongation can lead to a torsade de pointes-type ventricular arrhythmia, which can be fatal. The risk of torsade de pointes is related to the extent of QT prolongation, concomitant administration of QT prolonging medicinal products, a history of torsade de pointes, pre-existing QT interval prolongation, congestive heart failure, administration of potassium-wasting diuretics, or other conditions that result in hypokalaemia or hypomagnesaemia. One patient (receiving multiple, concomitant medicinal products, including amphotericin B) had asymptomatic torsade de pointes during induction therapy for relapsed APL with arsenic trioxide. She went onto consolidation without further evidence of QT prolongation.

In newly diagnosed patients, with low to intermediate risk APL, QTc prolongation was observed in 15.6%. In one patient induction treatment was terminated because of severe prolongation of the QTc interval and electrolyte abnormalities on day 3.

Peripheral neuropathy

Peripheral neuropathy, characterised by paraesthesia/dysaesthisia, is a common and well known effect of environmental arsenic. Only 2 relapsed/refractory APL patients discontinued treatment early due to this adverse event and one went on to receive additional arsenic trioxide on a subsequent protocol. Forty-four per cent of relapsed/refractory APL patients experienced symptoms that could be associated with neuropathy; most were mild to moderate and were reversible upon cessation of treatment with arsenic trioxide.

Hepatotoxicity (grade 3-4)

In newly diagnosed patients with low to intermediate risk APL 63.2% developed grade 3 or 4 hepatic toxic effects during induction or consolidation treatment with arsenic trioxide in combination with ATRA. However, toxic effects resolved with temporary discontinuation of either arsenic trioxide, ATRA or both.

Haematological and gastrointestinal toxicity

In newly diagnosed patients with low to intermediate risk APL, gastrointestinal toxicity, grade 3-4 neutropenia and grade 3 or 4 thrombocytopenia occurred, however these were 2.2 times less frequent in patients treated with arsenic trioxide in combination with ATRA compared to patients treated with ATRA + chemotherapy.