Get your patient on Bexarotene

Risk Summary

Bexarotene, a retinoid, can cause fetal harm based on findings from animal studies when administered to a pregnant female and is contraindicated during pregnancy. Bexarotene was teratogenic and caused developmental mortality in rats following oral administration during organogenesis [see Data] . Bexarotene must not be given to a pregnant female or a female who intends to become pregnant. If pregnancy does occur during treatment with bexarotene, immediately discontinue the drug and advise the pregnant female of the potential risk to a fetus.

The background risk of major birth defects and miscarriage for the indicated populations are unknown. However, the background risk in the U.S. general population of major birth defects is 2 to 4% and of miscarriage is 15 to 20% of clinically recognized pregnancies.

Data

Animal Data

Bexarotene caused malformations when administered orally to pregnant rats during days 7 to 17 of gestation. Developmental abnormalities included incomplete ossification at 4 mg/kg/day and cleft palate, depressed eye bulge/microphthalmia, and small ears at 16 mg/kg/day. The plasma AUC of bexarotene in rats at 4 mg/kg/day is approximately one third the AUC in humans at the recommended daily dose. At doses greater than 10 mg/kg/day, bexarotene caused developmental mortality. The no effect dose for fetal effects in rats was 1 mg/kg/day (producing an AUC approximately one sixth of the AUC at the recommended human daily dose).

Risk Summary

There is no information regarding the presence of bexarotene in human milk, the effects on the breast fed infant, or the effects on milk production. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from bexarotene, discontinue breastfeeding during treatment with bexarotene.

Pregnancy Testing

Obtain a negative serum pregnancy test (e.g., serum beta-human chorionic gonadotropin [beta-HCG]) with a sensitivity of at least 50 mlU/L within one week prior to bexarotene therapy. Obtain another pregnancy test at monthly intervals while the patient remains on bexarotene.

Contraception

Females

Bexarotene can cause fetal harm when administered to a pregnant female [see Use in Specific Populations (8.1)]. Females of reproductive potential should be advised to avoid becoming pregnant when bexarotene is used. Effective contraception must be used for one month prior to the initiation of therapy, during therapy and for at least one month following discontinuation of therapy; it is recommended that two reliable forms of contraception be used simultaneously unless abstinence is the chosen method. Bexarotene can potentially induce metabolic enzymes and thereby theoretically reduce the plasma concentrations of oral or other systemic hormonal contraceptives [see Drug Interactions (7)]. Thus, if treatment with bexarotene is intended in a female with reproductive potential, it is strongly recommended that one of the two reliable forms of contraception should be non-hormonal. Bexarotene therapy should be initiated on the second or third day of a normal menstrual period. No more than a one month supply of bexarotene should be given to the patient so that the results of pregnancy testing can be assessed and counseling regarding avoidance of pregnancy and birth defects can be reinforced.

Males

Male patients with sexual partners who are pregnant, possibly pregnant, or who could become pregnant must use condoms during sexual intercourse while taking bexarotene and for at least one month after the last dose of drug.

Safety and effectiveness of bexarotene in pediatric patients have not been established.

Of the total patients with CTCL in clinical trials of bexarotene, 64% were 60 years or older, while 33% were 70 years or older. No overall differences in safety were observed between patients 70 years or older and younger patients, but greater sensitivity of some older individuals to bexarotene cannot be ruled out. Responses to bexarotene were observed across all age group decades, without preference for any individual age group decade.

No specific studies have been conducted with bexarotene in subjects with hepatic impairment. Hepatic impairment is expected to lead to decreased clearance [see Clinical Pharmacology (12.3)]. If bexarotene is used in patients with hepatic impairment, monitor for signs of toxicity that may be due to increased exposure.

Bexarotene can cause fetal harm when administered to a pregnant female. Bexarotene is a member of the retinoid class of drugs that is associated with birth defects in humans and is contraindicated in females who are pregnant. Bexarotene was also teratogenic and caused developmental mortality when administered orally to pregnant rats. If this drug is used during pregnancy or if the patient becomes pregnant while taking this drug, the patient should be advised of the potential risk to a fetus.

Bexarotene capsules are contraindicated in patients with a known serious hypersensitivity to bexarotene or other components of the product.

Bexarotene induces substantial elevations in lipids in most patients. About 70% of patients with CTCL who received an initial dose of ≥300 mg/m ² /day of bexarotene had fasting triglyceride levels greater than 2.5 times the upper limit of normal. About 55% had values over 800 mg/dL with a median of about 1200 mg/dL in those patients. Cholesterol elevations above 300 mg/dL occurred in approximately 60% and 75% of patients with CTCL who received an initial dose of 300 mg/m ² /day or greater than 300 mg/m ² /day, respectively. Decreases in high density lipoprotein (HDL) cholesterol to less than 25 mg/dL were seen in about 55% and 90% of patients receiving an initial dose of 300 mg/m ² /day or greater than 300 mg/m ² /day, respectively, of bexarotene. Monitor lipid changes and treat abnormalities during therapy. The effects on triglycerides, HDL cholesterol, and total cholesterol were reversible with cessation of therapy, and could generally be mitigated by dose reduction and/or concomitant antilipemic therapy.

Perform fasting blood lipid determinations before bexarotene therapy is initiated and weekly until the lipid response to bexarotene is established, which usually occurs within two to four weeks, and monitor at eight week intervals thereafter. Fasting triglycerides should be normal or normalized with appropriate intervention prior to initiating bexarotene therapy. Maintain triglyceride levels below 400 mg/dL to reduce the risk of clinical sequelae [see Warnings and Precautions (5.2)]. If fasting triglycerides are elevated or become elevated during treatment, institute antilipemic therapy, and if necessary, reduce or interrupt the dose of bexarotene. In the 300 mg/m ² /day initial dose group, 60% of patients were given lipid lowering drugs. Atorvastatin was used in 48% (73/152) of patients with CTCL. Because of a potential drug-drug interaction, avoid gemfibrozil use with bexarotene [see Drug Interactions (7)].

Acute pancreatitis, including a fatal case, has been reported in four patients with CTCL and in six patients with non-CTCL cancers treated with bexarotene; the cases were associated with marked elevations of fasting serum triglycerides, the lowest being 770 mg/dL in one patient. One patient with advanced non-CTCL cancer died of pancreatitis. Interrupt bexarotene and evaluate if pancreatitis is suspected. Patients with CTCL who have risk factors for pancreatitis (e.g., prior pancreatitis, uncontrolled hyperlipidemia, excessive alcohol consumption, uncontrolled diabetes mellitus, biliary tract disease, and medications known to increase triglyceride levels or to be associated with pancreatic toxicity) may be at greater risk for pancreatitis associated with bexarotene [see Warnings and Precautions (5.1)].

Bexarotene caused elevations in liver chemistry tests (LFTs) in 5% (AST), 2% (ALT), and 0% (bilirubin) in patients with CTCL receiving an initial dose of 300 mg/m ² /day. In contrast, with an initial dose greater than 300 mg/m ² /day of bexarotene, the incidence of LFT elevations was higher at 7% (SGOT/AST), 9% (SGPT/ALT), and 6% (bilirubin). Two patients developed cholestasis, including one patient who died of liver failure. In clinical trials, elevated LFTs resolved within one month in 80% of patients following a decrease in dose or discontinuation of therapy. Obtain baseline LFTs and monitor LFTs after one, two and four weeks of treatment initiation, and if stable, at least every eight weeks thereafter during treatment. Interrupt or discontinue bexarotene if test results exceed three times the upper limit of normal values for AST, ALT, or bilirubin.

Bexarotene induces hypothyroidism in about half of all patients treated by causing a reversible reduction in levels of thyroid hormone (total thyroxine [total T4]) and thyroid-stimulating hormone (TSH). The incidence of decreases in TSH and total T4 were about 60% and 45%, respectively, in patients with CTCL receiving an initial dose of 300 mg/m ² /day. Hypothyroidism was reported as an adverse event in 29% of patients. Consider treatment with thyroid hormone supplementation in patients with hypothyroidism. In the 300 mg/m ² /day initial dose group, 37% of patients were treated with thyroid hormone replacement. Obtain baseline thyroid function tests and patients monitor during treatment.

Leukopenia in the range of 1000 to <3000 WBC x 10 ⁶ /L occurred in 18% of patients with CTCL receiving an initial dose of 300 mg/m ² /day of bexarotene. Patients receiving an initial dose greater than 300 mg/m ² /day of bexarotene had an incidence of leukopenia of 43%. No patient with CTCL treated with bexarotene developed leukopenia of less than 1000 WBC x 10 ⁶ /L. The usual time to onset of leukopenia was four to eight weeks after initiating bexarotene. The leukopenia observed in most patients was predominately neutropenia. In the 300 mg/m ² /day initial dose group, the incidence of NCI Grade 3 and Grade 4 neutropenia, respectively, was 12% and 4%. The leukopenia and neutropenia experienced during bexarotene therapy resolved after dose reduction or discontinuation of treatment, on average within 30 days in 93% of the patients with CTCL and 82% of patients with non-CTCL cancers. Leukopenia and neutropenia were rarely associated with severe sequelae or serious adverse events. Obtain complete blood counts (CBC) at baseline and periodically during treatment.

Posterior subcapsular cataracts occurred in preclinical toxicity studies in rats and dogs administered bexarotene daily for 6 months. New cataracts or worsening of previous cataracts occurred in 15 of 79 patients who were monitored with serial slit lamp examinations. Because of the high prevalence and rate of cataract formation in older patient populations, the relationship of bexarotene and cataracts cannot be determined in the absence of an appropriate control group. Patients treated with bexarotene who experience visual difficulties should have an appropriate ophthalmologic evaluation.

In clinical studies, patients were advised to limit vitamin A intake to ≤15,000 IU/day. Because of the relationship of bexarotene to vitamin A, patients should be advised to limit vitamin A supplements to avoid potential additive toxic effects.

In patients using insulin, agents enhancing insulin secretion (e.g., sulfonylureas), or insulin-sensitizers (e.g., thiazolidinedione class), based on the mechanism of action, bexarotene could enhance the action of these agents, resulting in hypoglycemia. Hypoglycemia has not been associated with the use of bexarotene as monotherapy.

Retinoids as a class have been associated with photosensitivity. In vitro assays indicate that bexarotene is a potential photosensitizing agent. Phototoxicity manifested as sunburn and skin sensitivity to sunlight occurred in patients who were exposed to direct sunlight while receiving bexarotene. Advise patients to minimize exposure to sunlight and artificial ultraviolet light while receiving bexarotene.

Before initiating bexarotene therapy, obtain a CBC, fasting lipid profile, liver function tests, and a thyroid profile. Fasting triglycerides should be normal or normalized with appropriate intervention prior to therapy. Monitor lab tests during bexarotene therapy as described above.

Hyperlipidemia usually occurs within the initial two to four weeks. Therefore, weekly lipid determinations are recommended during this interval. Subsequently, in patients not hyperlipidemic, determinations can be performed less frequently [see Warnings and Precautions (5.1)].

A white blood cell count with differential should be obtained at baseline and periodically during treatment. Baseline liver function tests should be obtained and should be carefully monitored after one, two and four weeks of treatment initiation, and if stable, periodically thereafter during treatment. Baseline thyroid function tests should be obtained and then monitored during treatment as indicated [see Warnings and Precautions (5.3, 5.4, 5.5, 5.6)].

CA125 assay values in patients with ovarian cancer may be increased by bexarotene therapy.

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety of bexarotene has been evaluated in two clinical trials of 152 patients with CTCL who received bexarotene for up to 97 weeks and in 352 patients in other trials. The mean duration of therapy for the 152 patients with CTCL was 166 days. The most common adverse events reported with an incidence of at least 10% in patients with CTCL treated at an initial dose of 300 mg/m ² /day of bexarotene are shown in Table 2. The events at least possibly related to treatment are lipid abnormalities (elevated triglycerides, elevated total and LDL cholesterol and decreased HDL cholesterol), hypothyroidism, headache, asthenia, rash, leukopenia, anemia, nausea, infection, peripheral edema, abdominal pain, and dry skin. Most adverse events occurred at a greater incidence in patients treated at starting doses of greater than 300 mg/m ² /day (see Table 2).

Adverse reactions leading to bexarotene dose reduction or discontinuation in at least two patients were hyperlipemia, neutropenia/leukopenia, diarrhea, fatigue/lethargy, hypothyroidism, headache, liver function test abnormalities, rash, pancreatitis, nausea, anemia, allergic reaction, muscle spasm, pneumonia, and confusion.

The NCI Grade 3 and NCI Grade 4 adverse reactions reported in two or more patients with CTCL treated at an initial dose of 300 mg/m ² /day of bexarotene (see Table 3) were hypertriglyceridemia, pruritus, headache, peripheral edema, leukopenia, rash, and hypercholesteremia. Most of these moderately severe or severe adverse events occurred at a higher rate in patients treated at starting doses of greater than 300 mg/m ² /day than in patients treated at a starting dose of 300 mg/m ² /day.

In patients with CTCL receiving an initial dose of 300 mg/m ² /day, the incidence of NCI Grade 3 or 4 elevations in triglycerides and total cholesterol was 28% and 25%, respectively (Table 4). In contrast, in patients with CTCL receiving greater than 300 mg/m ² /day, the incidence of NCI Grade 3 or 4 elevated triglycerides and total cholesterol was 45% and 45%, respectively. Other Grade 3 and 4 laboratory abnormalities are shown in Table 3.

In addition to the 152 patients enrolled in the two CTCL trials, 352 patients received bexarotene as monotherapy for various advanced malignancies at doses from 5 mg/m ² /day to 1000 mg/m ² /day. The common adverse reactions (incidence greater than 10%) were similar to those seen in patients with CTCL.

In the 504 patients (CTCL and non-CTCL) who received bexarotene as monotherapy, drug-related serious adverse reactions that were fatal, in one patient each, were acute pancreatitis, subdural hematoma, and liver failure.

In the patients with CTCL receiving an initial dose of 300 mg/m ² /day of bexarotene, adverse reactions reported at an incidence of less than 10% and not included in Tables 2 to 4 or discussed in other parts of labeling and possibly related to treatment were as follows:

Body as a Whole: chills , cellulitis, chest pain, breast pain, sepsis, and monilia infection.

Cardiovascular: hemorrhage, hypertension, angina pectoris, right heart failure, syncope, and tachycardia.

Digestive: constipation, dry mouth, flatulence, colitis, dyspepsia, cheilitis, gastroenteritis, gingivitis, liver failure, and melena.

Hemic and Lymphatic: eosinophilia, thrombocythemia, coagulation time increased, lymphocytosis, and thrombocytopenia.

Metabolic and Nutritional: LDH increased, creatinine increased, hypoproteinemia, hyperglycemia, weight decreased, weight increased, and amylase increased.

Musculoskeletal: arthralgia, myalgia, bone pain, myasthenia, and arthrosis.

Nervous: depression, agitation, ataxia, cerebrovascular accident, confusion, dizziness, hyperesthesia, hypesthesia, and neuropathy.

Respiratory: pharyngitis, rhinitis, dyspnea, pleural effusion, bronchitis, cough increased, lung edema, hemoptysis, and hypoxia.

Skin and Appendages: skin ulcer, acne, alopecia, skin nodule, macular papular rash, pustular rash, serous drainage, and vesicular bullous rash.

Special Senses: dry eyes, conjunctivitis, ear pain, blepharitis, corneal lesion, keratitis, otitis externa, and visual field defect.

Urogenital: albuminuria, hematuria, urinary incontinence, urinary tract infection, urinary urgency, dysuria, and kidney function abnormal.

The safety profile from the one post-approval trial with 59 subjects was generally comparable to that of the pivotal trials with the exception of serious adverse events hypertriglyceridemia, neutropenia and bone marrow failure which were observed more frequently in the bexarotene 300 mg/m ² /day group than in the bexarotene 150 mg/m ² /day group.

Severe hypertriglyceridemia (≥800 mg/dL) was not seen in any subject in the lower dosage arm.

The most common AEs by preferred term in either the bexarotene 300 or 150 mg/m ² /day treatment group were as follows: hypertriglyceridemia (18 subjects [62.1%] and 17 subjects [56.7%], respectively); hypothyroidism (15 subjects [51.7%] and 13 subjects [43.3%], respectively); headache (9 subjects[31.0%] and 7 subjects [23.3%], respectively); hypercholesterolemia (8 subjects [27.6%] and 7 subjects [23.3%], respectively); neutropenia (7 subjects [24.1%] and 2 subjects [6.7%], respectively); and skin exfoliation (5 subjects [17.2%] and 5 subjects [16.7%], respectively).

Higher percentage of subjects in the bexarotene 300 mg/m ² /day group than in the bexarotene 150 mg/m ² /day group experienced SAEs (13 subjects [44.8%] vs 11 subjects [36.7%], respectively.

Of the SAEs of special interest, there were more events in the bexarotene 300 mg/m ² /day group than in bexarotene 150 mg/m ² /day group of bone marrow failure (3 [10.3%] vs 1 [3.3%, respectively]), neutropenia (3 [10.3%] vs 0 [0%], respectively), and of hypertriglyceridemia (9 [31%] vs 2 [6.7%], respectively).

Bexarotene selectively binds and activates retinoid X receptor subtypes (RXRα, RXRβ, RXRγ). RXRs can form heterodimers with various receptor partners such as retinoic acid receptors (RARs), vitamin D receptor, thyroid receptor, and peroxisome proliferator activator receptors (PPARs). Once activated, these receptors function as transcription factors that regulate the expression of genes that control cellular differentiation and proliferation. Bexarotene inhibits the growth in vitro of some tumor cell lines of hematopoietic and squamous cell origin. It also induces tumor regression in vivo in some animal models. The exact mechanism of action of bexarotene in the treatment of cutaneous T-cell lymphoma (CTCL) is unknown.

Terminal half-life of bexarotene is approximately seven hours. Studies in patients with advanced malignancies show approximate single dose linearity within the therapeutic range.

Absorption

After oral administration of bexarotene, bexarotene is absorbed with a T _max of about two hours. Plasma bexarotene AUC and C _max values resulting from a 75 to 300 mg dose were 35% and 48% higher, respectively, after a fat-containing meal than after a glucose solution.

Distribution

Bexarotene is highly bound (>99%) to plasma proteins. The plasma proteins to which bexarotene binds have not been elucidated, and the ability of bexarotene to displace drugs bound to plasma proteins and the ability of drugs to displace bexarotene binding have not been studied

Elimination

Metabolism

Four bexarotene metabolites have been identified in plasma: 6-and 7-hydroxy-bexarotene and 6-and 7oxo-bexarotene. In vitro studies suggest that cytochrome P450 3A4 is the major cytochrome P450 responsible for formation of the oxidative metabolites and that the oxidative metabolites may be glucuronidated. The oxidative metabolites are active in in vitro assays of retinoid receptor activation, but the relative contribution of the parent and any metabolites to the efficacy and safety of bexarotene is unknown.

Excretion

The renal elimination of bexarotene and its metabolites was examined in patients with Type 2 diabetes mellitus. Urinary elimination of bexarotene and its known metabolites is a minor excretory pathway (<1% of administered dose).

Pharmacokinetics in Specific Populations

Age: Based on the population pharmacokinetic analysis of data for 232 patients aged ≥65 years and 343 patients aged <65 years, age has no statistically significant effect on bexarotene pharmacokinetics.

Body Weight and Gender: Based on the population pharmacokinetics analysis of data for 614 patients with a weight range of 26 to 145 kg, the bexarotene apparent clearance increases with increasing body weight. Gender has no statistically significant effect on bexarotene pharmacokinetics.

Race: Based on the population pharmacokinetic analysis of data for 540 Caucasian and 44 Black patients, bexarotene pharmacokinetics are similar in Blacks and Caucasians. There are insufficient data to evaluate potential differences in the pharmacokinetics of bexarotene for other races.

Renal Impairment: No formal studies have been conducted with bexarotene in patients with renal impairment. Urinary elimination of bexarotene and its known metabolites is a minor excretory pathway (<1% of administered dose), but because renal impairment can result in significant protein binding changes, pharmacokinetics may be altered in patients with renal impairment.

Hepatic Impairment: No specific studies have been conducted with bexarotene in patients with hepatic impairment. Because less than 1% of the dose is excreted in the urine unchanged and there is in vitro evidence of extensive hepatic contribution to bexarotene elimination, hepatic impairment would be expected to lead to greatly decreased clearance.

Drug Interactions

Effect of Other Drugs on bexarotene

CYP3A4 Inhibitors/Inducers: In a clinical study, concomitant administration of multiple doses of ketoconazole with bexarotene did not alter bexarotene plasma concentrations. This suggests that bexarotene elimination is not dependent on CYP3A4 metabolism.

Paclitaxel plus Carboplatin: The co-administration of paclitaxel (200 mg/m ² IV dose over 3 hours) plus carboplatin (at a dose expected to achieve an AUC of 6 mg•min/mL) with bexarotene (400 mg/m ² orally once daily) increased the exposure to bexarotene (AUC _0-24 and C _max ) by 2-fold compared to bexarotene alone .

Atorvastatin: Bexarotene concentrations were not affected by concomitant atorvastatin administration.

Effect of bexarotene on Other Drugs

Bexarotene did not significantly inhibit the following enzymes in human liver microsomes: CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4. In vitro data suggested a potential for bexarotene to inhibit CYP2C8 and induce CYP3A4.

Atorvastatin: The exposure (AUC) to atorvastatin (a substrate for CYP3A4) decreased by half when atorvastatin was co-administered with bexarotene (400 mg/m ² orally once daily).

Tamoxifen: Based on interim data, concomitant administration of bexarotene and tamoxifen resulted in approximately a 35% decrease in plasma concentrations of tamoxifen, possibly through induction of CYP3A4 by bexarotene.

Paclitaxel: The exposure (AUC) to paclitaxel (a substrate for CYP3A4 and CYP2C8) decreased by 19% when paclitaxel (200 mg/m ² IV dose over 3 hours) was co-administered with bexarotene (400 mg/m ² orally once daily).

Carboplatin: The co-administration of bexarotene (400 mg/m ² orally once daily) had no effect on the exposure to free or total carboplatin.

Long-term studies in animals to assess the carcinogenic potential of bexarotene have not been conducted. Bexarotene is not mutagenic to bacteria (Ames assay) or mammalian cells (mouse lymphoma assay). Bexarotene was not clastogenic in vivo (micronucleus test in mice).

No formal fertility studies were conducted with bexarotene. Bexarotene caused testicular degeneration when oral doses of 1.5 mg/kg/day were given to dogs for 91 days (producing an AUC of approximately one fifth the AUC at the recommended human daily dose).