2.1 Recommended Dose

Monotherapy

The recommended dose of fulvestrant injection is 500 mg to be administered intramuscularly into the buttocks (gluteal area) slowly (1 to 2 minutes per injection) as two 5 mL injections, one in each buttock, on Days 1, 15, 29 and once monthly thereafter [see Clinical Studies (14)].

Combination Therapy

When fulvestrant injection is used in combination with palbociclib, abemaciclib, or ribociclib, the recommended dose of fulvestrant injection is 500 mg to be administered intramuscularly into the buttocks (gluteal area) slowly (1 to 2 minutes per injection) as two 5 mL injections, one in each buttock, on Days 1, 15, 29 and once monthly thereafter.

When fulvestrant injection is used in combination with palbociclib, the recommended dose of palbociclib is a 125 mg capsule taken orally once daily for 21 consecutive days followed by 7 days off treatment to comprise a complete cycle of 28 days. Palbociclib should be taken with food. Refer to the Full Prescribing Information for palbociclib.

When fulvestrant injection is used in combination with abemaciclib, the recommended dose of abemaciclib is 150 mg orally, twice daily. Abemaciclib may be taken with or without food. Refer to the Full Prescribing Information for abemaciclib.

When fulvestrant injection is used in combination with ribociclib, the recommended dose of ribociclib is 600 mg taken orally, once daily for 21 consecutive days followed by 7 days off treatment resulting in a complete cycle of 28 days. Ribociclib can be taken with or without food. Refer to the Full Prescribing Information for ribociclib.

Pre/perimenopausal women treated with the combination of fulvestrant injection plus palbociclib, abemaciclib, or ribociclib, should be treated with luteinizing hormone-releasing hormone (LHRH) agonists according to current clinical practice standards [see Clinical Studies (14)].

2.2 Dose Modification

Monotherapy

Hepatic Impairment

A dose of 250 mg is recommended for patients with moderate hepatic impairment (Child-Pugh class B) to be administered intramuscularly into the buttock (gluteal area) slowly (1 to 2 minutes) as one 5 mL injection on Days 1, 15, 29 and once monthly thereafter.

Fulvestrant injection has not been evaluated in patients with severe hepatic impairment (Child-Pugh class C) [see Warnings and Precautions (5.2) and Use in Specific Populations (8.6)].

Combination Therapy

When fulvestrant injection is used in combination with palbociclib, abemaciclib, or ribociclib, refer to monotherapy dose modification instructions for fulvestrant injection.

Refer to the Full Prescribing Information of co-administered palbociclib, abemaciclib, or ribociclib for dose modification guidelines in the event of toxicities, for use with concomitant medications, and other relevant safety information.

2.3 Administration Technique

Administer the injection according to the local guidelines for performing large volume intramuscular injections.

NOTE: Due to the proximity of the underlying sciatic nerve, caution should be taken if administering fulvestrant injection at the dorsogluteal injection site [see Warnings and Precautions (5.3) and Adverse Reactions (6.1)].

The proper method of administration of fulvestrant injection for intramuscular use is described in the following instructions.

For each single-dose prefilled syringe:

1.

Remove glass syringe barrel from tray and check that it is not damaged.

2.

Remove perforated patient record label from syringe.

3.

Inspect drug product in glass syringe for any visible particulate matter or discoloration prior to use. Discard if particulate matter or discoloration is present.

4.

Peel open the safety needle (SafetyGlide™) outer packaging.

5.

Hold the syringe upright on the ribbed part (C). With the other hand, take hold of the cap (A) and carefully turn counterclockwise to unscrew the twist-off cap (A) (see Figure 1).

 

Figure 1

6.

Remove the protective cap (A) from the tip of the syringe barrel. DO NOT TOUCH THE STERILE SYRINGE TIP (Luer-Lok) (B) (see Figure 2).

Figure 2

7.

Attach the safety needle to the syringe tip (Luer-Lok). Twist needle until firmly seated (see Figure 3). Confirm that the needle is locked to the Luer connector before moving or tilting the syringe out of the vertical plane to avoid spillage of syringe contents.

Figure 3

For Administration:

8.

Pull shield straight off needle to avoid damaging needle point.

9.

Remove needle sheath.

10.

Expel excess gas from the syringe (a small gas bubble may remain).

11.

Administer intramuscularly slowly (1 to 2 minutes/injection) into the buttock (gluteal area). For user convenience, the needle ‘bevel up’ position is orientated to the lever arm, as shown in Figure 4.

Figure 4

12.

After injection, immediately activate the lever arm to deploy the needle shielding by applying a single-finger stroke to the activation assisted lever arm to push the lever arm completely forward. Listen for a click. Confirm that the needle shielding has completely covered the needle (see Figure 5). NOTE: Activate away from self and others.

Figure 5

13.

Discard the empty syringe into an approved sharps collector in accordance with applicable regulations and institutional policy.

14.

Repeat steps 1 through 13 for second syringe.

How To Use Fulvestrant Injection

For the 2 x 5 mL syringe package, the contents of both syringes must be injected to receive the 500 mg recommended dose.

SAFETYGLIDE™ INSTRUCTIONS FROM BECTON DICKINSON

SafetyGlide™ is a trademark of Becton Dickinson and Company.

Important Administration Information

To help avoid HIV (AIDS), HBV (Hepatitis), and other infectious diseases due to accidental needlesticks, contaminated needles should not be recapped or removed, unless there is no alternative or that such action is required by a specific medical procedure. Hands must remain behind the needle at all times during use and disposal.

Do not autoclave SafetyGlide™ Needle before use.

Becton Dickinson guarantees the contents of their unopened or undamaged packages to be sterile, non-toxic, and non-pyrogenic.

5.1 Risk of Bleeding

Because fulvestrant is administered intramuscularly, it should be used with caution in patients with bleeding diatheses, thrombocytopenia, or anticoagulant use.

5.2 Increased Exposure in Patients with Hepatic Impairment

The safety and pharmacokinetics of fulvestrant were evaluated in a study in seven subjects with moderate hepatic impairment (Child-Pugh class B) and seven subjects with normal hepatic function. Exposure was increased in patients with moderate hepatic impairment, therefore, a dose of 250 mg is recommended [see Dosage and Administration (2.2)].

Fulvestrant has not been studied in patients with severe hepatic impairment (Child-Pugh class C) [see Use in Specific Populations (8.6)].

5.3 Injection Site Reaction

Injection site related events including sciatica, neuralgia, neuropathic pain, and peripheral neuropathy have been reported with fulvestrant injection. Caution should be taken while administering fulvestrant at the dorsogluteal injection site due to the proximity of the underlying sciatic nerve [see Dosage and Administration (2.3) and Adverse Reactions (6.1)].

5.4 Embryo-Fetal Toxicity

Based on findings from animal studies and its mechanism of action, fulvestrant can cause fetal harm when administered to a pregnant woman. In animal reproduction studies, administration of fulvestrant to pregnant rats and rabbits during organogenesis resulted in embryo-fetal toxicity at daily doses that are significantly less than the maximum recommended human dose. Advise pregnant women of the potential risk to a fetus. Advise females of reproductive potential to use effective contraception during treatment with fulvestrant and for one year after the last dose [see Use in Specific Populations(8.1), (8.3) and Clinical Pharmacology (12.1)].

5.5 Immunoassay Measurement of Serum Estradiol

Due to structural similarity of fulvestrant and estradiol, fulvestrant can interfere with estradiol measurement by immunoassay, resulting in falsely elevated estradiol levels.

6.1 Clinical Trials Experience

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

Monotherapy

Comparison of Fulvestrant 500 mg and Fulvestrant 250 mg (CONFIRM)

The following adverse reactions (ARs) were calculated based on the safety analysis of CONFIRM comparing the administration of fulvestrant 500 mg intramuscularly once a month with fulvestrant 250 mg intramuscularly once a month. The most frequently reported adverse reactions in the fulvestrant 500 mg group were injection site pain (11.6% of patients), nausea (9.7% of patients), and bone pain (9.4% of patients); the most frequently reported adverse reactions in the fulvestrant 250 mg group were nausea (13.6% of patients), back pain (10.7% of patients), and injection site pain (9.1% of patients).

Table 1 lists adverse reactions reported with an incidence of 5% or greater, regardless of assessed causality, from CONFIRM.

Table 1: Adverse Reactions in CONFIRM (≥5% in Either Treatment Group)

In the pooled safety population (N=1127) from clinical trials comparing fulvestrant 500 mg to fulvestrant 250 mg, post-baseline increases of ≥1 CTC grade in either AST, ALT, or alkaline phosphatase were observed in >15% of patients receiving fulvestrant. Grade 3 to 4 increases were observed in 1 to 2% of patients. The incidence and severity of increased hepatic enzymes (ALT, AST, ALP) did not differ between the 250 mg and the 500 mg fulvestrant arms.

Comparison of Fulvestrant 500 mg and Anastrozole 1 mg (FALCON)

The safety of fulvestrant 500 mg versus anastrozole 1 mg was evaluated in FALCON. The data described below reflect exposure to fulvestrant in 228 out of 460 patients with HR-positive advanced breast cancer in postmenopausal women not previously treated with endocrine therapy who received at least one (1) dose of treatment in FALCON.

Permanent discontinuation associated with an adverse reaction occurred in 4 of 228 (1.8%) patients receiving fulvestrant, and in 3 of 232 (1.3%) patients receiving anastrozole. Adverse reactions leading to discontinuation for those patients receiving fulvestrant included drug hypersensitivity (0.9%), injection site hypersensitivity (0.4%), and elevated liver enzymes (0.4%).

The most common adverse reactions (≥10%) of any grade reported in patients in the fulvestrant arm were arthralgia, hot flash, fatigue, and nausea.

Adverse reactions reported in patients who received fulvestrant in FALCON at an incidence of ≥5% in either treatment arm are listed in Table 2, and laboratory abnormalities are listed in Table 3.

Table 2: Adverse Reactions in FALCON

Table 3: Laboratory Abnormalities in FALCON*

*In FALCON, post-baseline increases of ≥1 CTC grade in either AST, ALT, or alkaline phosphatase were observed in >10% of patients receiving fulvestrant. Grade 3 to 4 increases were observed in 1% to 3% of patients.

Comparison of Fulvestrant 250 mg and Anastrozole 1 mg in Combined Trials (Studies 0020 and 0021)

The most commonly reported adverse reactions in the fulvestrant and anastrozole treatment groups were gastrointestinal symptoms (including nausea, vomiting, constipation, diarrhea, and abdominal pain), headache, back pain, vasodilatation (hot flashes), and pharyngitis.

Injection site reactions with mild transient pain and inflammation were seen with fulvestrant and occurred in 7% of patients given the single 5 mL injection (Study 0020) and in 27% of patients given the 2 x 2.5 mL injections (Study 0021) in the two clinical trials that compared fulvestrant 250 mg and anastrozole 1 mg.

Table 4 lists adverse reactions reported with an incidence of 5% or greater, regardless of assessed causality, from the two controlled clinical trials comparing the administration of fulvestrant 250 mg intramuscularly once a month with anastrozole 1 mg orally once a day.

*Including more severe injection site related sciatica, neuralgia, neuropathic pain, and peripheral neuropathy. All patients on fulvestrant received injections, but only those anastrozole patients who were in Study 0021 received placebo injections.

Combination Therapy

Combination Therapy with Palbociclib (PALOMA-3)

The safety of fulvestrant 500 mg plus palbociclib 125 mg/day versus fulvestrant plus placebo was evaluated in PALOMA-3. The data described below reflect exposure to fulvestrant plus palbociclib in 345 out of 517 patients with HR-positive, HER2-negative advanced or metastatic breast cancer who received at least 1 dose of treatment in PALOMA-3. The median duration of treatment for fulvestrant plus palbociclib was 10.8 months while the median duration of treatment for fulvestrant plus placebo arm was 4.8 months.

No dose reduction was allowed for fulvestrant in PALOMA-3. Dose reductions of palbociclib due to an adverse reaction of any grade occurred in 36% of patients receiving fulvestrant plus palbociclib.

Permanent discontinuation associated with an adverse reaction occurred in 19 of 345 (6%) patients receiving fulvestrant plus palbociclib, and in 6 of 172 (3%) patients receiving fulvestrant plus placebo. Adverse reactions leading to discontinuation for those patients receiving fulvestrant plus palbociclib included fatigue (0.6%), infections (0.6%), and thrombocytopenia (0.6%).

The most common adverse reactions (≥10%) of any grade reported in patients in the fulvestrant plus palbociclib arm by descending frequency were neutropenia, leukopenia, infections, fatigue, nausea, anemia, stomatitis, diarrhea, thrombocytopenia, vomiting, alopecia, rash, decreased appetite, and pyrexia.

The most frequently reported Grade ≥3 adverse reactions (≥5%) in patients receiving fulvestrant plus palbociclib in descending frequency were neutropenia and leukopenia.

Adverse reactions (≥10%) reported in patients who received fulvestrant plus palbociclib or fulvestrant plus placebo in PALOMA-3 are listed in Table 5, and laboratory abnormalities are listed in Table 6.

Table 5: Adverse Reactions (≥10%) in PALOMA-3

Additional adverse reactions occurring at an overall incidence of <10.0% of patients receiving fulvestrant plus palbociclib in PALOMA-3 included asthenia (7.5%), aspartate aminotransferase increased (7.5%), dysgeusia (6.7%), epistaxis (6.7%), lacrimation increased (6.4%), dry skin (6.1%), alanine aminotransferase increased (5.8%), vision blurred (5.8%), dry eye (3.8%), and febrile neutropenia (0.9%).

Table 6: Laboratory Abnormalities in PALOMA-3

Combination Therapy with Abemaciclib (MONARCH 2)

The safety of fulvestrant (500 mg) plus abemaciclib (150 mg twice daily) versus fulvestrant plus placebo was evaluated in MONARCH 2. The data described below reflect exposure to fulvestrant in 664 patients with HR-positive, HER2-negative advanced breast cancer who received at least one dose of fulvestrant plus abemaciclib or placebo in MONARCH 2.

Median duration of treatment was 12 months for patients receiving fulvestrant plus abemaciclib and 8 months for patients receiving fulvestrant plus placebo.

Dose reductions due to an adverse reaction occurred in 43% of patients receiving fulvestrant plus abemaciclib. Adverse reactions leading to dose reductions ≥5% of patients were diarrhea and neutropenia. Abemaciclib dose reduction due to diarrhea of any grade occurred in 19% of patients receiving fulvestrant plus abemaciclib compared to 0.4% of patients receiving fulvestrant plus placebo. Abemaciclib dose reductions due to neutropenia of any grade occurred in 10% of patients receiving fulvestrant plus abemaciclib compared to no patients receiving fulvestrant plus placebo.

Permanent study treatment discontinuation due to an adverse event was reported in 9% of patients receiving fulvestrant plus abemaciclib and in 3% of patients receiving fulvestrant plus placebo. Adverse reactions leading to permanent discontinuation for patients receiving fulvestrant plus abemaciclib were infection (2%), diarrhea (1%), hepatotoxicity (1%), fatigue (0.7%), nausea (0.2%), abdominal pain (0.2%), acute kidney injury (0.2%), and cerebral infarction (0.2%).

Deaths during treatment or during the 30-day follow up, regardless of causality, were reported in 18 cases (4%) of fulvestrant plus abemaciclib treated patients versus 10 cases (5%) of fulvestrant plus placebo treated patients. Causes of death for patients receiving fulvestrant plus abemaciclib included: 7 (2%) patient deaths due to underlying disease, 4 (0.9%) due to sepsis, 2 (0.5%) due to pneumonitis, 2 (0.5%) due to hepatotoxicity, and one (0.2%) due to cerebral infarction.

The most common adverse reactions reported (≥20%) in the fulvestrant plus abemaciclib arm were diarrhea, fatigue, neutropenia, nausea, infections, abdominal pain, anemia, leukopenia, decreased appetite, vomiting, and headache (Table 7). The most frequently reported (≥5%) Grade 3 or 4 adverse reactions were neutropenia, diarrhea, leukopenia, anemia, and infections.

 

Table 7: Adverse Reactions ≥10% of Patients Receiving Fulvestrant Plus Abemaciclib and ≥2% Higher Than Fulvestrant Plus Placebo in MONARCH 2

Additional adverse reactions in MONARCH 2 include venous thromboembolic events (deep vein thrombosis, pulmonary embolism, cerebral venous sinus thrombosis, subclavian vein thrombosis, axillary vein thrombosis, and DVT inferior vena cava), which were reported in 5% of patients treated with fulvestrant plus abemaciclib as compared to 0.9% of patients treated with fulvestrant plus placebo.

 

Table 8: Laboratory Abnormalities ≥10% in Patients Receiving Fulvestrant Plus Abemaciclib and ≥2% Higher Than Fulvestrant Plus Placebo in MONARCH 2

Combination Therapy with Ribociclib (MONALEESA-3)

The safety of fulvestrant 500 mg plus ribociclib 600 mg versus fulvestrant plus placebo was evaluated in MONALEESA-3. The data described below reflect exposure to fulvestrant plus ribociclib in 483 out of 724 postmenopausal patients with HR-positive, HER2-negative advanced or metastatic breast cancer for initial endocrine based therapy or after disease progression on endocrine therapy who received at least one dose of fulvestrant plus ribociclib or placebo in MONALEESA-3. Median duration of treatment was 15.8 months for fulvestrant plus ribociclib and 12 months for fulvestrant plus placebo.

Dose reductions due to adverse reactions occurred in 32% of patients receiving fulvestrant plus ribociclib and in 3% of patients receiving fulvestrant plus placebo. Among patients receiving fulvestrant plus ribociclib, 8% were reported to have permanently discontinued both fulvestrant plus ribociclib, and 9% were reported to have discontinued ribociclib alone due to ARs. Among patients receiving fulvestrant plus placebo, 4% were reported to have permanently discontinued both fulvestrant and placebo and 2% were reported to have discontinued placebo alone due to ARs.

Adverse reactions leading to treatment discontinuation of fulvestrant plus ribociclib (as compared to fulvestrant plus placebo) were ALT increased (5% vs. 0%), AST increased (3% vs. 0.6%), and vomiting (1% vs. 0%).

The most common adverse reactions (reported at a frequency ≥20% on the fulvestrant plus ribociclib arm and ≥2% higher than fulvestrant plus placebo) were neutropenia, infections, leukopenia, cough, nausea, diarrhea, vomiting, constipation, pruritus, and rash. The most frequently reported Grade ¾ adverse reactions (reported at a frequency ≥5%) in patients receiving fulvestrant plus ribociclib in descending frequency were neutropenia, leukopenia, infections, and abnormal liver function tests.

Adverse reactions and laboratory abnormalities occurring in patients in MONALEESA-3 are listed in Table 9 and Table 10, respectively.

 

Table 9: Adverse Reactions Occurring in ≥10% and ≥2% higher than fulvestrant plus Placebo Arm in MONALEESA-3 (All Grades)

Additional adverse reactions in MONALEESA-3 for patients receiving fulvestrant plus ribociclib included asthenia (14%), dyspepsia (10%), thrombocytopenia (9%), dry skin (8%), dysgeusia (7%), electrocardiogram QT prolonged (6%), dry mouth (5%), vertigo (5%), dry eye (5%), lacrimation increased (4%), erythema (4%), hypocalcemia (4%), blood bilirubin increased (1%), and syncope (1%).

Table 10: Laboratory Abnormalities Occurring in ≥10% of Patients in MONALEESA-3

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of fulvestrant. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

For fulvestrant 250 mg, other adverse reactions reported as drug-related and seen infrequently (<1%) include thromboembolic phenomena, myalgia, vertigo, leukopenia, and hypersensitivity reactions, including angioedema and urticaria.

Vaginal bleeding has been reported infrequently (<1%), mainly in patients during the first 6 weeks after changing from existing hormonal therapy to treatment with fulvestrant. If bleeding persists, further evaluation should be considered.

Elevation of bilirubin, elevation of gamma GT, hepatitis, and liver failure have been reported infrequently (<1%).

8.1 Pregnancy

Risk Summary

Based on findings from animal studies and its mechanism of action, fulvestrant can cause fetal harm when administered to a pregnant woman [see Clinical Pharmacology (12.1)]. There are no available data in pregnant women to inform the drug-associated risk. In animal reproduction studies, administration of fulvestrant to pregnant rats and rabbits during organogenesis caused embryo-fetal toxicity, including skeletal malformations and fetal loss, at daily doses that were 6% and 30% of the maximum recommended human dose based on mg/m2, respectively [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. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.

Data

Animal Data

Administration of fulvestrant to rats prior to and up to implantation caused embryonic loss at daily doses that were 0.6% of the daily maximum recommended human dose based on mg/m2. When fulvestrant was administered to pregnant rats during the period of organogenesis, intramuscular doses ≥0.1 mg/kg/day (6% of the human recommended dose based on mg/m2) caused effects on embryo-fetal development consistent with its antiestrogenic activity. Fulvestrant caused an increased incidence of fetal abnormalities in rats (tarsal flexure of the hind paw at 2 mg/kg/day; equivalent to the human dose based on mg/m2) and non-ossification of the odontoid and ventral tubercle of the first cervical vertebra at doses ≥0.1 mg/kg/day. Fulvestrant administered at 2 mg/kg/day caused fetal loss.

When administered to pregnant rabbits during the period of organogenesis, fulvestrant caused pregnancy loss at an intramuscular dose of 1 mg/kg/day (equivalent to the human dose based on mg/m2). Further, at 0.25 mg/kg/day (30% the human dose based on mg/m2), fulvestrant caused increases in placental weight and post-implantation loss in rabbits. Fulvestrant was associated with an increased incidence of fetal variations in rabbits (backwards displacement of the pelvic girdle, and 27 pre-sacral vertebrae at 0.25 mg/kg/day; 30% the human dose based on mg/m2) when administered during the period of organogenesis.

8.2 Lactation

Risk Summary

There is no information regarding the presence of fulvestrant in human milk, nor of its effects on milk production or breastfed infant. Fulvestrant can be detected in rat milk [see Data]. Because of the potential for serious adverse reactions in breastfed infants from fulvestrant, advise a lactating woman not to breastfeed during treatment with fulvestrant and for one year after the final dose.

Data

Levels of fulvestrant were approximately 12-fold higher in milk than in plasma after exposure of lactating rats to a dose of 2 mg/kg. Drug exposure in rodent pups from fulvestrant-treated lactating dams was estimated as 10% of the administered dose. In a study in rats of fulvestrant at 10 mg/kg given twice or 15 mg/kg given once (less than the recommended human dose based on mg/m2) during lactation, offspring survival was slightly reduced.

8.3 Females and Males of Reproductive Potential

Pregnancy Testing

Pregnancy testing is recommended for females of reproductive potential within seven days prior to initiating fulvestrant.

Contraception

Females

Fulvestrant can cause fetal harm when administered to a pregnant woman [see Use in Specific Populations (8.1)]. Advise females of reproductive potential to use effective contraception during treatment and for one year after the last dose.

Infertility

Based on animal studies, fulvestrant may impair fertility in females and males of reproductive potential. The effects of fulvestrant on fertility were reversible in female rats [see Nonclinical Toxicology (13.1)].

8.4 Pediatric Use

Safety and effectiveness in pediatric patients have not been established. A multi-center, single-arm, open-label, study of fulvestrant was conducted in 30 girls with McCune-Albright Syndrome (MAS) associated with Progressive Precocious Puberty (PPP). The median age at informed consent was 6 years old (range: 1 to 8).

The first 10 patients initially received fulvestrant 2 mg/kg. Based on PK data from the first 6 patients, all 10 patients receiving 2 mg/kg were escalated to a dose of 4 mg/kg and all other patients received 4 mg/kg from study entry.

Baseline measurements for vaginal bleeding days, bone age, growth velocity, and Tanner staging for at least 6 months prior to study entry were provided retrospectively by the parent, guardian, or local consultant. All measurements during the study period were collected prospectively. Patients’ baseline characteristics included the following: a mean ± SD chronological age of 5.9±1.8 years; a mean rate of bone age advancement (change in bone age in years divided by change in chronological age in years) of 2±1.03; and a mean growth velocity z-score of 2.4±3.26.

Twenty-nine of 30 patients completed the 12-month study period. The following results were observed: 35% (95% CI: 16%, 57%) of the 23 patients with baseline vaginal bleeding experienced a complete cessation of vaginal bleeding on-treatment (month 0 to 12); a reduction in the rate of bone age advancement during the 12-month study period compared to baseline (mean change = -0.9 [95% CI: -1.4, -0.4]); and a reduction in mean growth velocity Z-score on-treatment compared to baseline (mean change = -1.1 [95% CI: -2.7, 0.4]). There were no clinically meaningful changes in median Tanner stage (breast or pubic), mean uterine volume, or mean ovarian volume, or predicted adult height (PAH) on-treatment compared to baseline. The effect of fulvestrant on bone mineral density in children has not been studied and is not known.

Eight patients (27%) experienced adverse reactions that were considered possibly related to fulvestrant. These included injection site reactions (inflammation, pain, hematoma, pruritus, rash), abdominal pain, contusion, tachycardia, hot flash, extremity pain, and vomiting. Nine (30%) patients reported an SAE, none of which were considered related to fulvestrant. No patients discontinued study treatment due to an AE and no patients died.

Pharmacokinetics

The pharmacokinetics of fulvestrant was characterized using a population pharmacokinetic analysis with sparse samples per patient obtained from 30 female pediatric patients aged 1 to 8 years with PPP associated with MAS. Pharmacokinetic data from 294 postmenopausal women with breast cancer who received 125 or 250 mg monthly dosing regimen were also included in the analysis.

In these pediatric patients receiving 4 mg/kg monthly intramuscular dose of fulvestrant, the geometric mean (SD) CL/F was 444 (165) mL/min which was 32% lower than adults. The geometric mean (SD) steady state trough concentration (Cmin,ss) and AUCss was 4.19 (0.87) ng/mL and 3680 (1020) ng·hr/mL, respectively.

8.5 Geriatric Use

For fulvestrant 250 mg, when tumor response was considered by age, objective responses were seen in 22% and 24% of patients under 65 years of age and in 11% and 16% of patients 65 years of age and older, who were treated with fulvestrant in Study 0021 and Study 0020, respectively.

8.6 Hepatic Impairment

Fulvestrant is metabolized primarily in the liver.

The pharmacokinetics of fulvestrant were evaluated after a single dose of 100 mg in subjects with mild and moderate hepatic impairment and normal hepatic function (n=7 subjects/group), using a shorter-acting intramuscular injection formulation. Subjects with mild hepatic impairment (Child-Pugh class A) had comparable mean AUC and clearance values to those with normal hepatic function. In subjects with moderate hepatic impairment (Child-Pugh class B), the average AUC of fulvestrant increased by 70% compared to patients with normal hepatic function. AUC was positively correlated with total bilirubin concentration (p=0.012). Fulvestrant has not been studied in patients with severe hepatic impairment (Child-Pugh class C).

A dose of fulvestrant 250 mg is recommended in patients with moderate hepatic impairment (Child-Pugh class B) [see Dosage and Administration (2.2) and Warnings and Precautions (5.2)].

8.7 Renal Impairment

Negligible amounts of fulvestrant are eliminated in urine; therefore, a study in patients with renal impairment was not conducted. In the advanced breast cancer trials, fulvestrant concentrations in women with estimated creatinine clearance as low as 30 mL/min were similar to women with normal creatinine.

12.1 Mechanism of Action

Many breast cancers have estrogen receptors (ER) and the growth of these tumors can be stimulated by estrogen. Fulvestrant is an estrogen receptor antagonist that binds to the estrogen receptor in a competitive manner with affinity comparable to that of estradiol and downregulates the ER protein in human breast cancer cells.

In vitro studies demonstrated that fulvestrant is a reversible inhibitor of the growth of tamoxifen-resistant, as well as estrogen-sensitive human breast cancer (MCF-7) cell lines. In in vivo tumor studies, fulvestrant delayed the establishment of tumors from xenografts of human breast cancer MCF-7 cells in nude mice. Fulvestrant inhibited the growth of established MCF-7 xenografts and of tamoxifen-resistant breast tumor xenografts.

Fulvestrant showed no agonist-type effects in in vivo uterotrophic assays in immature or ovariectomized mice and rats. In in vivo studies in immature rats and ovariectomized monkeys, fulvestrant blocked the uterotrophic action of estradiol. In postmenopausal women, the absence of changes in plasma concentrations of FSH and LH in response to fulvestrant treatment (250 mg monthly) suggests no peripheral steroidal effects.

12.2 Pharmacodynamics

In a clinical study in postmenopausal women with primary breast cancer treated with single doses of fulvestrant 15 to 22 days prior to surgery, there was evidence of increasing down-regulation of ER with increasing dose. This was associated with a dose-related decrease in the expression of the progesterone receptor, an estrogen-regulated protein. These effects on the ER pathway were also associated with a decrease in Ki67 labeling index, a marker of cell proliferation.

12.3 Pharmacokinetics

Absorption

The single dose and multiple dose PK parameters for the 500 mg dosing regimen with an additional dose (AD) at Day 15 are reported in Table 11. The additional dose of fulvestrant given two weeks after the initial dose allows for steady state concentrations to be reached within the first month of dosing.

Distribution

The apparent volume of distribution at steady state is approximately 3 to 5 L/kg. This suggests that distribution is largely extravascular. Fulvestrant is highly (99%) bound to plasma proteins; VLDL, LDL, and HDL lipoprotein fractions appear to be the major binding components. The role of sex hormone-binding globulin, if any, could not be determined.

Metabolism

Biotransformation and disposition of fulvestrant in humans have been determined following intramuscular and intravenous administration of 14C-labeled fulvestrant. Metabolism of fulvestrant appears to involve combinations of a number of possible biotransformation pathways analogous to those of endogenous steroids, including oxidation, aromatic hydroxylation, conjugation with glucuronic acid and/or sulphate at the 2, 3 and 17 positions of the steroid nucleus, and oxidation of the side chain sulphoxide. Identified metabolites are either less active or exhibit similar activity to fulvestrant in antiestrogen models.

Studies using human liver preparations and recombinant human enzymes indicate that cytochrome P-450 3A4 (CYP 3A4) is the only P-450 isoenzyme involved in the oxidation of fulvestrant; however, the relative contribution of P-450 and non-P-450 routes in vivo is unknown.

Excretion

Fulvestrant was rapidly cleared by the hepatobiliary route with excretion primarily via the feces (approximately 90%). Renal elimination was negligible (less than 1%). After an intramuscular injection of 250 mg, the clearance (Mean ± SD) was 690 ± 226 mL/min with an apparent half-life about 40 days.

Special Populations

Geriatric

In patients with breast cancer, there was no difference in fulvestrant pharmacokinetic profile related to age (range 33 to 89 years).

Gender

Following administration of a single intravenous dose, there were no pharmacokinetic differences between men and women or between premenopausal and postmenopausal women. Similarly, there were no differences between men and postmenopausal women after intramuscular administration.

Race

In the advanced breast cancer treatment trials, the potential for pharmacokinetic differences due to race have been evaluated in 294 women including 87.4% Caucasian, 7.8% Black, and 4.4% Hispanic. No differences in fulvestrant plasma pharmacokinetics were observed among these groups. In a separate trial, pharmacokinetic data from postmenopausal ethnic Japanese women were similar to those obtained in non-Japanese patients.

Drug-Drug Interactions

There are no known drug-drug interactions. Fulvestrant does not significantly inhibit any of the major CYP isoenzymes, including CYP 1A2, 2C9, 2C19, 2D6, and 3A4 in vitro, and studies of co-administration of fulvestrant with midazolam indicate that therapeutic doses of fulvestrant have no inhibitory effects on CYP 3A4 or alter blood levels of drug metabolized by that enzyme. Although fulvestrant is partly metabolized by CYP 3A4, a clinical study with rifampin, an inducer of CYP 3A4, showed no effect on the pharmacokinetics of fulvestrant. Also, results from a healthy volunteer study with ketoconazole, a potent inhibitor of CYP 3A4, indicated that ketoconazole had no effect on the pharmacokinetics of fulvestrant and dosage adjustment is not necessary in patients co-prescribed CYP 3A4 inhibitors or inducers [see Drug Interactions (7)]. Data from a clinical trial in patients with breast cancer showed that there was no clinically relevant drug interaction when fulvestrant is co-administered with palbociclib, abemaciclib, or ribociclib.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Two-year carcinogenesis studies were conducted in rats and mice. Positive findings were observed in both species. Rats were treated at intramuscular doses of 15 mg/kg/30 days, 10 mg/rat/30 days, and 10 mg/rat/15 days.

These doses correspond to 0.9-, 1.5-, and 3-fold (in females) and 0.8-, 0.8-, and 2-fold (in males) the systemic exposure [AUC0-30 days] achieved in women receiving the recommended dose of 500 mg/month. An increased incidence of benign ovarian granulosa cell tumors and testicular Leydig cell tumors was evident, in females dosed at 10 mg/rat/15 days and males dosed at 15 mg/rat/30 days, respectively. Mice were treated at oral doses of 0, 20, 150 and 500 mg/kg/day. These doses correspond to 0-, 0.8-, 8.4-, and 18-fold (in females) and 0.8-, 7.1-, and 11.9- fold (in males), the systemic exposure (AUC0-30 days) achieved in women receiving the recommended dose of 500 mg/month. There was an increased incidence of sex cord stromal tumors (both benign and malignant) in the ovary of mice at doses of 150 and 500 mg/kg/day. Induction of such tumors is consistent with the pharmacology-related endocrine feedback alterations in gonadotropin levels caused by an antiestrogen.

Fulvestrant was not mutagenic or clastogenic in multiple in vitro tests with and without the addition of a mammalian liver metabolic activation factor (bacterial mutation assay in strains of Salmonella typhimurium and Escherichia coli, in vitro cytogenetics study in human lymphocytes, mammalian cell mutation assay in mouse lymphoma cells and in vivo micronucleus test in rat).

In female rats, fulvestrant administered at doses ≥0.01 mg/kg/day (0.6% the human recommended dose based on body surface area [BSA in mg/m2]), for 2 weeks prior to and for 1 week following mating, caused a reduction in fertility and embryonic survival. No adverse effects on female fertility and embryonic survival were evident in female animals dosed at 0.001 mg/kg/day (0.06% the human dose based on BSA in mg/m2). Restoration of female fertility to values similar to controls was evident following a 29-day withdrawal period after dosing at 2 mg/kg/day (equivalent to the human dose based on BSA in mg/m2). The effects of fulvestrant on the fertility of female rats appear to be consistent with its antiestrogenic activity. The potential effects of fulvestrant on the fertility of male animals were not studied, but in a 6-month toxicology study, male rats treated with intramuscular doses of 15 mg/kg/30 days, 10 mg/rat/30 days, or 10 mg/rat/15 days fulvestrant showed a loss of spermatozoa from the seminiferous tubules, seminiferous tubular atrophy, and degenerative changes in the epididymides. Changes in the testes and epididymides had not recovered 20 weeks after cessation of dosing. These fulvestrant doses correspond to 1.3-, 1.2-, and 3.5-fold the systemic exposure [AUC0-30 days] achieved in women receiving the recommended dose of 500 mg/month.