AstraZeneca has announced that the FDA ( Food and Drug Administration ) has approved the orphan drug Vandetanib ( Zactima ) for the treatment of medullary thyroid cancer that cannot be removed by surgery or that has spread to other parts of the body.

Vandetanib is a kinase inhibitor indicated for the treatment of symptomatic or progressive medullary thyroid cancer in patients with unresectable locally advanced or metastatic disease. The use of Vandetanib in patients with indolent, asymptomatic or slowly progressing disease should be carefully considered because of the treatment-related risks.

The approval of Zactima is based on the results of the ZETA study, a phase III, double-blind trial that randomized 331 patients with unresectable locally advanced or metastatic medullary thyroid cancer to Vandetanib 300 mg ( n=231 ) or placebo ( n=100 ).
In the study, patients randomized to Vandetanib showed a statistically significant improvement in progression-free survival ( PFS ) when compared to those randomized to placebo ( hazard ratio, HR=0.35; p<0.0001 ).
This difference reflects a 65% reduction in risk for disease progression.
Median progression-free survival was 16.4 months in the placebo arm and at least 22.6 months in the Vandetanib arm.
At the primary PFS analysis, no significant overall survival difference was noted. QT prolongation, torsades de pointes, and sudden death are included in the boxed warning for Vandetanib.
The most common adverse drug reactions ( greater than 20% ) seen in the ZETA trial with Vandetanib were diarrhea ( 57% ), rash ( 53% ), acne ( 35% ), nausea ( 33% ), hypertension ( 33% ), headache ( 26% ), fatigue ( 24% ), decreased appetite ( 21% ), and abdominal pain ( 21% ).

A Risk Evaluation and Mitigation Strategy ( REMS ) is required for Zactima due to the risks of QT prolongation, torsades de pointes, and sudden death. Only prescribers and pharmacies who are certified through the Zactima REMS program, a restricted distribution program, will be able to prescribe and dispense Vandetanib.

Important safety information, including boxed WARNING

Warning QT prolongation, torsades de pointes and sudden death

• Vandetanib can prolong the QT interval. Torsades de pointes and sudden death have been reported in patients receiving Vandetanib;

• Vandetanib should not be used in patients with hypocalcemia, hypokalemia, hypomagnesemia, or long QT syndrome. Hypocalcemia, hypokalemia and/or hypomagnesemia must be corrected prior to Vandetanib administration and should be periodically monitored;

• Drugs known to prolong the QT interval should be avoided. If a drug known to prolong the QT interval must be administered, more frequent ECG monitoring is recommended;

• Given the half-life of 19 days, ECGs should be obtained to monitor the QT at baseline, at 2-4 weeks and 8-12 weeks after starting treatment with Vandetanib and every 3 months thereafter. Following any dose reduction for QT prolongation, or any dose interruptions greater than 2 weeks, QT assessment should be conducted as described above;

• Because of the 19-day half-life, adverse reactions including a prolonged QT interval may not resolve quickly. Monitor appropriately;

• Do not use Vandetanib in patients with congenital long QT syndrome;

• Because of the risk of QT prolongation, ECGs and levels of serum potassium, calcium, magnesium, and TSH should be monitored at baseline, at 2-4 weeks and 8-12 weeks after starting treatment with Vandetanib, and every 3 months thereafter and following dose adjustments;

• Severe skin reactions ( including Stevens-Johnson syndrome ), some leading to death, have been reported and may prompt permanent discontinuation of Vandetanib;

• Interstitial lung disease ( ILD ) has been observed with Vandetanib and deaths have been reported. Interrupt Vandetanib treatment and investigate unexplained dyspnea, cough, and fever;

• Ischemic cerebrovascular events, serious hemorrhagic events, and heart failure have been observed with Vandetanib and some cases have been fatal;

• Diarrhea has been observed with Vandetanib. Serum electrolytes and ECGs should be carefully monitored in cases of diarrhea because of the risk of QT prolongation with Vandetanib. If severe diarrhea develops, Vandetanib treatment should be stopped until diarrhea improves;

• Hypothyroidism, hypertension, and reversible posterior leukoencephalopathy syndrome ( RPLS ) have been observed with Vandetanib;

• The concomitant use of known strong CYP3A4 inducers may reduce drug levels of Vandetanib and should be avoided. The administration of Vandetanib with antiarrhythmic drugs and other drugs that may prolong the QT interval should be avoided;

• Vandetanib exposure is increased in patients with impaired renal function. The starting dose of Vandetanib should be reduced to 200 mg in patients with moderate to severe renal impairment and the QT interval should be monitored closely;

• Vandetanib is not recommended for patients with moderate and severe hepatic impairment, since safety and efficacy have not been established;

• Vandetanib can cause fetal harm when administered to a pregnant woman. Women of childbearing potential should be advised to avoid pregnancy while receiving Vandetanib and for at least 4 months following treatment;

• The most common laboratory abnormalities ( greater than 20% ) were decreased calcium ( 57% ), increased ALT ( 51% ), and decreased glucose ( 24% ).

Source: AstraZeneca, 2011

XagenaMedicine2011