Vorinostat Other names: Suberoylanilide hydroxamic acid Suberanilohydroxamic acid

Risk Summary

Based on its mechanism of action and findings from animal studies, vorinostat can cause fetal harm when administered to a pregnant woman.

There are insufficient data on vorinostat use in pregnant women to inform a drug-associated risk of major birth defects and miscarriage. In animal reproduction studies, administration of vorinostat to pregnant rats and rabbits during the period of organogenesis caused adverse developmental outcomes at maternal exposures approximately 0.5 times the human exposure based on AUC_{0-24 hours} (see Data). Advise pregnant women of the potential risk to a fetus.

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Data

Animal Data

Results of animal studies indicate that vorinostat crosses the placenta and is found in fetal plasma at levels up to 50% of maternal concentrations. Doses up to 50 and 150 mg/kg/day were tested in rats and rabbits, respectively (~0.5 times the human exposure based on AUC_{0-24 hours}). Treatment-related developmental effects including decreased mean live fetal weights, incomplete ossifications of the skull, thoracic vertebra, sternebra, and skeletal variations (cervical ribs, supernumerary ribs, vertebral count and sacral arch variations) were seen in rats at the highest dose of vorinostat tested. Reductions in mean live fetal weight and an elevated incidence of incomplete ossification of the metacarpals were seen in rabbits dosed at 150 mg/kg/day. The no observed effect levels (NOELs) for these findings were 15 and 50 mg/kg/day (<0.1 times the human exposure based on AUC) in rats and rabbits, respectively. A dose-related increase in the incidence of malformations of the gall bladder was noted in all drug treatment groups in rabbits versus the concurrent control.

Risk Summary

There are no data on the presence of vorinostat or its metabolites in human milk, the effects on a breastfed child, or the effects on milk production. Because many drugs are excreted in human milk and because of the potential for serious adverse drug reactions in a nursing child, advise lactating women not to breastfeed during treatment with vorinostat and for at least 1 week after the last dose.

Carcinogenicity studies have not been performed with vorinostat.

Vorinostat was mutagenic in vitro in the bacterial reverse mutation assays (Ames test), caused chromosomal aberrations in vitro in Chinese hamster ovary (CHO) cells and increased the incidence of micro-nucleated erythrocytes when administered to mice (Mouse Micronucleus Assay).

Treatment-related effects on female reproduction were identified in the oral fertility study when females were dosed for 14 days prior to mating through gestational day 7. Doses of 15, 50 and 150 mg/kg/day to rats resulted in approximate exposures of 0.15, 0.36 and 0.70 times the expected clinical exposure based on AUC. Dose-dependent increases in corpora lutea were noted at ≥15 mg/kg/day, which resulted in increased peri-implantation losses at ≥50 mg/kg/day. At 150 mg/kg/day, there were increases in the incidences of dead fetuses and in resorptions.

No effects on reproductive performance or fertility were observed in male rats dosed (20, 50, 150 mg/kg/day; approximate exposures of 0.15, 0.36 and 0.70 times the expected clinical exposure based on AUC) for 70 days prior to mating with untreated females.

The following serious adverse reactions have been associated with vorinostat in clinical trials and are discussed in greater detail in other sections of the label:

• Thromboembolism
• Myelosuppression
• Gastrointestinal Toxicity
• Hyperglycemia
• Clinical Chemistry Abnormalities
• Severe thrombocytopenia when combined with other Histone Deacetylase (HDAC) Inhibitors

Clinical Trials Experience

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 vorinostat was evaluated in 107 CTCL patients in two single arm clinical studies in which 86 patients received 400 mg once daily.

The data described below reflect exposure to vorinostat 400 mg once daily in the 86 patients for a median number of 97.5 days on therapy (range 2 to 480+ days). Seventeen (19.8%) patients were exposed beyond 24 weeks and 8 (9.3%) patients were exposed beyond 1 year. The population of CTCL patients studied was 37 to 83 years of age, 47.7% female, 52.3% male, and 81.4% white, 16.3% black, and 1.2% Asian or multi-racial.

Common Adverse Reactions

The most common drug-related adverse reactions can be classified into 4 symptom complexes: gastrointestinal symptoms (diarrhea, nausea, anorexia, weight decrease, vomiting, constipation), constitutional symptoms (fatigue, chills), hematologic abnormalities (thrombocytopenia, anemia), and taste disorders (dysgeusia, dry mouth). The most common serious drug-related adverse reactions were pulmonary embolism and anemia.

Table 1 summarizes the frequency of CTCL patients with specific adverse reactions, using the National Cancer Institute-Common Terminology Criteria for Adverse Events (NCI-CTCAE, version 3.0).

Table 1. Clinical or Laboratory Adverse Reactions Occurring in CTCL Patients (Incidence ≥10% of patients):

The frequencies of more severe thrombocytopenia, anemia and fatigue were increased at doses higher than 400 mg once daily of vorinostat.

Serious Adverse Reactions

The most common serious adverse reactions in the 86 CTCL patients in two clinical trials were pulmonary embolism reported in 4.7% (4/86) of patients, squamous cell carcinoma reported in 3.5% (3/86) of patients and anemia reported in 2.3% (2/86) of patients. There were single events of cholecystitis, death (of unknown cause), deep vein thrombosis, enterococcal infection, exfoliative dermatitis, gastrointestinal hemorrhage, infection, lobar pneumonia, myocardial infarction, ischemic stroke, pelviureteric obstruction, sepsis, spinal cord injury, streptococcal bacteremia, syncope, T-cell lymphoma, thrombocytopenia and ureteric obstruction.

Discontinuations

Of the CTCL patients who received the 400-mg once daily dose, 9.3% (8/86) of patients discontinued vorinostat due to adverse reactions. These adverse reactions, regardless of causality, included anemia, angioneurotic edema, asthenia, chest pain, exfoliative dermatitis, death, deep vein thrombosis, ischemic stroke, lethargy, pulmonary embolism, and spinal cord injury.

Dose Modifications

Of the CTCL patients who received the 400-mg once daily dose, 10.5% (9/86) of patients required a dose modification of vorinostat due to adverse reactions. These adverse reactions included increased serum creatinine, decreased appetite, hypokalemia, leukopenia, nausea, neutropenia, thrombocytopenia and vomiting. The median time to the first adverse reactions resulting in dose reduction was 42 days (range 17 to 263 days).

Laboratory Abnormalities

Laboratory abnormalities were reported in all of the 86 CTCL patients who received the 400-mg once-daily dose.

Increased serum glucose was reported as a laboratory abnormality in 69% (59/86) of CTCL patients who received the 400-mg once daily dose; only 4 of these abnormalities were severe (Grade 3). Increased serum glucose was reported as an adverse reaction in 8.1% (7/86) of CTCL patients who received the 400-mg once daily dose.

Transient increases in serum creatinine were detected in 46.5% (40/86) of CTCL patients who received the 400-mg once daily dose. Of these laboratory abnormalities, 34 were NCI CTCAE Grade 1, 5 were Grade 2, and 1 was Grade 3.

Proteinuria was detected as a laboratory abnormality (51.4%) in 38 of 74 patients tested. The clinical significance of this finding is unknown.

Dehydration

Based on reports of dehydration as a serious drug-related adverse reaction in clinical trials, patients were instructed to drink at least 2 L/day of fluids for adequate hydration.

Adverse Reactions in Non-CTCL Patients

The frequencies of individual adverse reactions were substantially higher in the non-CTCL population. Drug-related serious adverse reactions reported in the non-CTCL population which were not observed in the CTCL population included single events of blurred vision, asthenia, hyponatremia, tumor hemorrhage, Guillain-Barré syndrome, renal failure, urinary retention, cough, hemoptysis, hypertension, and vasculitis.

In patients recovering from bowel surgery and treated perioperatively with vorinostat, anastomotic healing complications including fistulas, perforations, and abscess formation have occurred.