CLINICAL PHARMACOLOGY
Mechanism Of Action
Erdafitinib is a kinase
inhibitor that binds to and inhibits enzymatic activity of FGFR1, FGFR2, FGFR3
and FGFR4 based on in vitro data. Erdafitinib also binds to RET, CSF1R, PDGFRA,
PDGFRB, FLT4, KIT, and VEGFR2. Erdafitinib inhibited FGFR phosphorylation and
signaling and decreased cell viability in cell lines expressing FGFR genetic
alterations, including point mutations, amplifications, and fusions.
Erdafitinib demonstrated antitumor activity in FGFR-expressing cell lines and
xenograft models derived from tumor types, including bladder cancer.
Pharmacodynamics
Cardiac Electrophysiology
Based on evaluation of QTc interval in an open-label,
dose escalation and dose expansion study in 187 patients with cancer,
erdafitinib had no large effect (i.e., > 20 ms) on the QTc interval.
Serum Phosphate
Erdafitinib increased serum phosphate level as a
consequence of FGFR inhibition. BALVERSA should be increased to the maximum
recommended dose to achieve target serum phosphate levels of 5.5– 7.0 mg/dL in
early cycles with continuous daily dosing [see DOSAGE AND ADMINISTRATION].
In erdafitinib clinical trials, the use of drugs which
can increase serum phosphate levels, such as potassium phosphate supplements,
vitamin D supplements, antacids, phosphate-containing enemas or laxatives, and
medications known to have phosphate as an excipient were prohibited unless no
alternatives exist. To manage phosphate elevation, phosphate binders were
permitted. Avoid concomitant use with agents that can alter serum phosphate
levels before the initial dose increase period based on serum phosphate levels [see
DRUG INTERACTIONS].
Pharmacokinetics
Following administration of 8 mg once daily, the mean
(coefficient of variation [CV%]) erdafitinib steady-state maximum observed
plasma concentration (Cmax), area under the curve (AUCtau), and minimum
observed plasma concentration (Cmin) were 1,399 ng/mL (51%), 29,268 ng•h/mL
(60%), and 936 ng/mL (65%), respectively.
Following single and repeat once daily dosing,
erdafitinib exposure (maximum observed plasma concentration [Cmax] and area
under the plasma concentration time curve [AUC]) increased proportionally
across the dose range of 0.5 to 12 mg (0.06 to 1.3 times the maximum approved
recommended dose). Steady state was achieved after 2 weeks with once daily
dosing and the mean accumulation ratio was 4-fold.
Absorption
Median time to achieve peak plasma concentration (tmax)
was 2.5 hours (range: 2 to 6 hours).
Effect Of Food
No clinically meaningful differences with erdafitinib
pharmacokinetics were observed following administration of a high-fat and
high-calorie meal (800 calories to 1,000 calories with approximately 50% of
total caloric content of the meal from fat) in healthy subjects.
Distribution
The mean apparent volume of distribution of erdafitinib
was 29 L in patients.
Erdafitinib protein binding was 99.8% in patients,
primarily to alpha-1-acid glycoprotein.
Elimination
The mean total apparent clearance (CL/F) of erdafitinib
was 0.362 L/h in patients. The mean effective half-life of erdafitinib was 59
hours in patients.
Metabolism
Erdafitinib is primarily metabolized by CYP2C9 and
CYP3A4. The contribution of CYP2C9 and CYP3A4 in the total clearance of
erdafitinib is estimated to be 39% and 20% respectively. Unchanged erdafitinib
was the major drug-related moiety in plasma, there were no circulating
metabolites.
Excretion
Following a single oral dose of radiolabeled erdafitinib,
approximately 69% of the dose was recovered in feces (19% as unchanged) and 19%
in urine (13% as unchanged).
Specific Populations
No clinically meaningful trends in the pharmacokinetics
of erdafitinib were observed based on age (2188 years), sex, race, body weight
(36-132 kg), mild (eGFR [estimated glomerular filtration rate, using
modification of diet in renal disease equation] 60 to 89 mL/min/1.73 m²) or
moderate (eGFR 30-59 mL/min/1.73 m²) renal impairment or mild hepatic
impairment (total bilirubin ≤ ULN and AST > ULN, or total bilirubin
> 1.0–1.5 x ULN and any AST).
The pharmacokinetics of erdafitinib in patients with
severe renal impairment, renal impairment requiring dialysis, moderate or
severe hepatic impairment is unknown.
Drug Interaction Studies
Clinical Studies and Model-Based Approaches
Strong CYP2C9 Inhibitors
Erdafitinib mean ratios (90% CI) for Cmax and AUCinf were
121% (99.9, 147) and 148% (120, 182), respectively, when co-administered with
fluconazole, a strong CYP2C9 inhibitor and moderate CYP3A4 inhibitor, relative
to erdafitinib alone.
Strong CYP3A4 Inhibitors
Erdafitinib mean ratios (90% CI) for Cmax and AUCinf were
105% (86.7, 127) and 134% (109, 164), respectively, when co-administered with
itraconazole (a strong CYP3A4 inhibitor and P-gp inhibitor) relative to
erdafitinib alone.
Strong CYP3A4/2C9 Inducers
Simulations suggested that rifampicin (a strong
CYP3A4/2C9 inducer) may significantly decrease erdafitinib Cmax and AUC.
In Vitro Studies
CYP Substrates
Erdafitinib is a time dependent inhibitor and inducer of
CYP3A4. The effect of erdafitinib on a sensitive CYP3A4 substrate is unknown.
Erdafitinib is not an inhibitor of other major CYP isozymes at clinically
relevant concentrations.
Transporters
Erdafitinib is a substrate and inhibitor of P-gp. P-gp
inhibitors are not expected to affect erdafitinib exposure to a clinically
relevant extent. Erdafitinib is an inhibitor of OCT2.
Erdafitinib does not inhibit BCRP, OATP1B, OATP1B3, OAT1,
OAT3, OCT1, MATE-1, or MATE-2K at clinically relevant concentrations.
Acid-Lowering Agents
Erdafitinib has adequate solubility across the pH range
of 1 to 7.4. Acid-lowering agents (e.g., antacids, H2-antagonists, proton pump
inhibitors) are not expected to affect the bioavailability of erdafitinib.
Pharmacogenomics
CYP2C9 activity is reduced in individuals with genetic
variants, such as the CYP2C9*2 and CYP2C9*3 polymorphisms. Erdafitinib exposure
was similar in subjects with CYP2C9*1/*2 and *1/*3 genotypes relative to
subjects with CYP2C9*1/*1 genotype (wild type). No data are available in
subjects characterized by other genotypes (e.g., *2/*2, *2/*3, *3/*3).
Simulation suggested no clinically meaningful differences in erdafitinib
exposure in subjects with CYP2C9*2/*2 and *2/*3 genotypes. The exposure of
erdafitinib is predicted to be 50% higher in subjects with the CYP2C9*3/*3
genotype, estimated to be present in 0.4% to 3% of the population among various
ethnic groups.
Clinical Studies
Urothelial Carcinoma With Susceptible FGFR Genetic
Alterations
Study BLC2001 (NCT02365597) was a multicenter,
open-label, single-arm study to evaluate the efficacy and safety of BALVERSA in
patients with locally advanced or metastatic urothelial carcinoma (mUC).
Fibroblast growth factor receptor (FGFR) mutation status for screening and
enrollment of patients was determined by a clinical trial assay (CTA). The
efficacy population consists of a cohort of eighty-seven patients who were
enrolled in this study with disease that had progressed on or after at least
one prior chemotherapy and that had at least 1 of the following genetic
alterations: FGFR3 gene mutations (R248C, S249C, G370C, Y373C) or FGFR gene
fusions (FGFR3-TACC3, FGFR3BAIAP2L1, FGFR2-BICC1, FGFR2-CASP7), as determined
by the CTA performed at a central laboratory. Tumor samples from 69 patients
were tested retrospectively by the QIAGEN therascreen® FGFR RGQ RT-PCR Kit,
which is the FDA-approved test for selection of patients with mUC for BALVERSA.
Patients received a starting dose of BALVERSA at 8 mg
once daily with a dose increase to 9 mg once daily in patients whose serum
phosphate levels were below the target of 5.5 mg/dL between days 14 and 17; a
dose increase occurred in 41% of patients. BALVERSA was administered until
disease progression or unacceptable toxicity. The major efficacy outcome
measures were objective response rate (ORR) and duration of response (DoR), as
determined by blinded independent review committee (BIRC) according to RECIST
v1.1.
The median age was 67 years (range: 36 to 87 years), 79%
were male, and 74% were Caucasian. Most patients (92%) had a baseline Eastern
Cooperative Oncology Group (ECOG) performance status of 0 or 1. Sixty-six
percent of patients had visceral metastases. Eighty-four (97%) patients
received at least one of cisplatin or carboplatin previously. Fifty-six percent
of patients only received prior cisplatin-based regimens, 29% received only
prior carboplatin-based regimens, and 10% received both cisplatin and carboplatin-based
regimens. Three (3%) patients had disease progression following prior
platinum-containing neoadjuvant or adjuvant therapy only. Twenty-four percent
of patients had been treated with prior anti PD-L1/PD-1 therapy.
Efficacy results are summarized in Table 7 and Table 8.
Overall response rate was 32.2%. Responders included patients who had
previously not responded to anti PD-L1/PD-1 therapy.
Table 7: Efficacy Results
Endpoint |
BIRCa assessment
N=87 |
ORR (95% CI) |
32.2% (22.4, 42.0) |
Complete response (CR) |
2.3% |
Partial response (PR) |
29.9% |
Median DoR in months (95% CI) |
5.4 (4.2, 6.9) |
a BIRC: Blinded Independent Review Committee
ORR = CR + PR
CI = Confidence Interval |
Table 8: Efficacy Results by FGFR Genetic Alteration
FGFR3 Point Mutation |
BIRCa assessment
N=64 |
ORR (95% CI) |
40.6% (28.6, 52.7) |
FGFR3 Fusion b c |
N=18 |
ORR (95% CI) |
11.1% (0, 25.6) |
FGFR2 Fusion c |
N=6 |
ORR |
0 |
a BIRC: Blinded Independent Review Committee
b Both responders had FGFR3-TACC3_V1 fusion
c One patient with a FGFR2-CASP7/FGFR3-TACC3_V3 fusion is reported
in both FGFR2 fusion and FGFR3 fusion above
ORR = CR + PR
CI = Confidence Interval |