CLINICAL PHARMACOLOGY
Mechanism Of Action
Romidepsin is a histone deacetylase (HDAC) inhibitor. HDACs catalyze the removal of acetyl groups from acetylated lysine residues in histones, resulting in the
modulation of gene expression. HDACs also deacetylate non-histone proteins, such as transcription factors. In vitro, romidepsin causes the accumulation of acetylated
histones, and induces cell cycle arrest and apoptosis of some cancer cell lines with IC50 values in the nanomolar range. The mechanism of the antineoplastic effect of
romidepsin observed in nonclinical and clinical studies has not been fully characterized.
Pharmacodynamics
Cardiac Electrophysiology
At doses of 14 mg/m2 as a 4-hour intravenous infusion, and at doses of 8 (0.57 times the recommended dose), 10 (0.71 times the recommended dose) or 12 (0.86 times
the recommended dose) mg/m2 as a 1-hour infusion, no large changes in the mean QTc interval (>20 milliseconds) from baseline based on Fridericia correction method
were detected. Small increase in mean QT interval (< 10 milliseconds) and mean QT interval increase between 10 to 20 milliseconds cannot be excluded.
Romidepsin was associated with a delayed concentration-dependent increase in heart rate in patients with advanced cancer with a maximum mean increase in heart rate
of 20 beats per minute occurring at the 6-hour time point after start of romidepsin infusion for patients receiving 14 mg/m2 as a 4-hour infusion.
Pharmacokinetics
In patients with T-cell lymphomas who received 14 mg/m2 of romidepsin intravenously over a 4-hour period on days 1, 8, and 15 of a 28-day cycle, geometric mean
values of the maximum plasma concentration (Cmax) and the area under the plasma concentration versus time curve (AUC0-∞) were 377 ng/mL and 1549 ng*hr/mL,
respectively. Romidepsin exhibited linear pharmacokinetics across doses ranging from 1.0 (0.07 times the recommended dose) to 24.9 (1.76 times the recommended
dose) mg/m2 when administered intravenously over 4 hours in patients with advanced cancers.
Distribution
Romidepsin is highly protein bound in plasma (92% to 94%) over the concentration range of 50 ng/mL to 1000 ng/mL with α1-acid-glycoprotein (AAG) being the
principal binding protein. Romidepsin is a substrate of the efflux transporter P-glycoprotein (P-gp, ABCB1).
In vitro, romidepsin accumulates into human hepatocytes via an unknown active uptake process. Romidepsin is not a substrate of the following uptake transporters:
BCRP, BSEP, MRP2, OAT1, OAT3, OATP1B1, OATP1B3, or OCT2. In addition, romidepsin is not an inhibitor of BCRP, MRP2, MDR1 or OAT3. Although
romidepsin did not inhibit OAT1, OCT2, and OATP1B3 at concentrations seen clinically (1 μmol/L), modest inhibition was observed at 10 μmol/L. Romidepsin was
found to be an inhibitor of BSEP and OATP1B1.
Metabolism
Romidepsin undergoes extensive metabolism in vitro primarily by CYP3A4 with minor contribution from CYP3A5, CYP1A1, CYP2B6, and CYP2C19. At therapeutic
concentrations, romidepsin did not competitively inhibit CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, or CYP3A4 in vitro.
At therapeutic concentrations, romidepsin did not cause notable induction of CYP1A2, CYP2B6 and CYP3A4 in vitro. Therefore, pharmacokinetic drug-drug
interactions are unlikely to occur due to CYP450 induction or inhibition by romidepsin when co-administered with CYP450 substrates.
Excretion
Following 4-hour intravenous administration of romidepsin at 14 mg/m2 on days 1, 8, and 15 of a 28-day cycle in patients with T-cell lymphomas, the terminal half-life
(t1/2) was approximately 3 hours. No accumulation of plasma concentration of romidepsin was observed after repeated dosing.
Drug Interactions
Ketoconazole
Following co-administration of 8 mg/m2 ISTODAX (4-hour infusion) with ketoconazole, the overall romidepsin exposure was increased by
approximately 25% and 10% for AUC0-∞ and Cmax, respectively, compared to romidepsin alone, and the difference in AUC0-∞ between the 2 treatments was statistically
significant.
Rifampin
Following co-administration of 14 mg/m2 ISTODAX (4-hour infusion) with rifampin, the overall romidepsin exposure was increased by approximately 80%
and 60% for AUC0-∞ and Cmax, respectively, compared to romidepsin alone, and the difference between the 2 treatments was statistically significant. Co-administration
of rifampin decreased the romidepsin clearance and volume of distribution by 44% and 52%, respectively. The increase in exposure seen after co-administration with
rifampin is likely due to rifampin’s inhibition of an undetermined hepatic uptake process that is predominant for the disposition of ISTODAX.
Drugs That Inhibit P-Glycoprotein
Drugs that inhibit p-glycoprotein may increase the concentration of romidepsin.
Specific Populations
Effect Of Age, Gender, Race Or Renal Impairment
The pharmacokinetics of romidepsin was not influenced by age (27 to 83 yrs), gender, race (white vs. black) or mild (estimated creatinine clearance 50 - 80 mL/min),
moderate (estimated creatinine clearance 30-50 mL/min), or severe (estimated creatinine clearance <30 mL/min) renal impairment. The effect of end-stage renal disease
(estimated creatine clearance less than 15 mL/min) on romidepsin pharmacokinetics has not been studied.
Hepatic Impairment
Romidepsin clearance decreased with increased severity of hepatic impairment. In patients with cancer, the geometric mean Cmax values after administration of 14, 7,
and 5 mg/m2 romidepsin in patients with mild (B1: bilirubin ≤ULN and AST >ULN; B2: bilirubin >ULN but ≤1.5 x ULN and any AST), moderate (bilirubin >1.5 x
ULN to ≤3 x ULN and any AST), and severe (bilirubin >3 x ULN and any AST) hepatic impairment were approximately 111%, 96%, and 86% of the corresponding
value after administration of 14 mg/m2 romidepsin in patients with normal (bilirubin ≤upper limit of normal (ULN) and aspartate aminotransferase (AST) ≤ULN)
hepatic function, respectively. The geometric mean AUCinf values in patients with mild, moderate, and severe hepatic impairment were approximately 144%, 114%, and
116% of the corresponding value in patients with normal hepatic function, respectively. Among these 4 cohorts, moderate interpatient variability was noted for the
exposure parameters Cmax and AUCinf, as the coefficient of variation (CV) ranged from 30% to 54%.
Clinical Studies
Cutaneous T-Cell Lymphoma
ISTODAX was evaluated in 2 multicenter, single-arm clinical studies in patients with CTCL. Overall, 167 patients with CTCL were treated in the US, Europe, and
Australia. Study 1 included 96 patients with confirmed CTCL after failure of at least 1 prior systemic therapy. Study 2 included 71 patients with a primary diagnosis of
CTCL who received at least 2 prior skin directed therapies or one or more systemic therapies. Patients were treated with ISTODAX at a starting dose of 14 mg/m2
infused over 4 hours on days 1, 8, and 15 every 28 days.
In both studies, patients could be treated until disease progression at the discretion of the investigator and local regulators. Objective disease response was evaluated
according to a composite endpoint that included assessments of skin involvement, lymph node and visceral involvement, and abnormal circulating T-cells (“Sézary
cells”).
The primary efficacy endpoint for both studies was overall objective disease response rate (ORR) based on the investigator assessments, and defined as the proportion
of patients with confirmed complete response (CR) or partial response (PR). CR was defined as no evidence of disease and PR as ≥ 50% improvement in disease.
Secondary endpoints in both studies included duration of response and time to response.
Baseline Patient Characteristics
Demographic and disease characteristics of the patients in Study 1 and Study 2 are provided in Table 4.
Table 4. Baseline Patient Characteristics
(CTCL Population)
Characteristic |
Study 1
(N=96) |
Study 2
(N=71) |
Age |
N |
96 |
71 |
Mean (SD) |
57 (12) |
56 (13) |
Median (Range) |
57 (21, 89) |
57 (28, 84) |
Sex, n (%) |
Men |
59 (61) |
48 (68) |
Women |
37 (39) |
23 (32) |
Race, n (%) |
White |
90 (94) |
55 (77) |
Black |
5 (5) |
15 (21) |
Other/Not Reported |
1 (1) |
1 (1) |
Stage of Disease at Study Entry, n (%) |
IA |
0 (0) |
1 (1) |
IB |
15 (16) |
6 (9) |
IIA |
13 (14) |
2 (3) |
IIB |
21(22) |
14 (20) |
III |
23 (24) |
9 (13) |
IVA |
24 (25) |
27 (38) |
IVB |
0 (0) |
12 (17) |
Number of Prior Skin-Directed Therapies |
Median (Range) |
2 (0, 6) |
1 (0, 3) |
Number of Prior Systemic Therapies |
Median (Range) |
2 (1, 8) |
2 (0, 7) |
Clinical Results
Efficacy outcomes for CTCL patients are provided in Table 5. Median time to first response was 2 months (range 1 to 6) in both studies. Median time to CR was 4
months in Study 1 and 6 months in Study 2 (range 2 to 9).
Table 5. Clinical Results for CTCL Patients
Response Rate |
Study 1
(N=96) |
Study 2
(N=71) |
ORR (CR + PR), n (%) |
33 (34) |
25 (35) |
[95% Confidence Interval] |
[25, 45] |
[25, 49] |
CR, n (%) |
6 (6) |
4 (6) |
[95% Confidence Interval] |
[2, 13] |
[2, 14] |
PR, n (%) |
27 (28) |
21 (30) |
[95% Confidence Interval] |
[19, 38] |
[20, 43] |
Duration of Response (months) |
|
|
N |
33 |
25 |
Median (range) |
15 (1, 20*) |
11 (1, 66*) |
*Denotes censored value. |
Peripheral T-Cell Lymphoma
ISTODAX was evaluated in a multicenter, single-arm, international clinical study in patients with PTCL who had failed at least 1 prior systemic therapy (Study 3).
Patients in US, Europe, and Australia were treated with ISTODAX at a dose of 14 mg/m2 infused over 4 hours on days 1, 8, and 15 every 28 days. Of the 131 patients
treated, 130 patients had histological confirmation by independent central review and were evaluable for efficacy (HC Population). Six cycles of treatment were
planned; patients who developed progressive disease (PD), significant toxicity, or who met another criterion for study termination were to discontinue treatment.
Responding patients had the option of continuing treatment beyond 6 cycles at the discretion of the patient and Investigator until study withdrawal criteria were met.
Primary assessment of efficacy was based on rate of complete response (CR + CRu) as determined by an Independent Review Committee (IRC) using the International
Workshop Response Criteria (IWC). Secondary measures of efficacy included IRC assessment of duration of response and objective disease response (ORR, CR + CRu
+ PR).
Baseline Patient Characteristics
Demographic and disease characteristics of the PTCL patients are provided in Table 6.
Table 6. Baseline Patient Characteristics
(PTCL Population)
Characteristic |
Study 3
(N=130) |
Study 4
(N=47) |
Age (years), n |
130 |
47 |
Mean (SD) |
59 (13) |
59 (13) |
Median |
61 |
59 |
Sex, n (%) |
|
|
Male |
88 (68) |
25 (53) |
Female |
42 (32) |
22 (47) |
Race, n (%) |
|
|
White |
116 (89) |
40 (85) |
Black |
7 (5) |
4 (9) |
Asian |
3 (2) |
3 (6) |
Other |
4 (3) |
0 |
PTCL Subtype Based on Central Diagnosis, n (%) |
|
|
PTCL Unspecified (NOS) |
69 (53) |
28 (60) |
Angioimmunoblastic T-cell lymphoma (AITL) |
27 (21) |
7 (15) |
ALK-1 negative anaplastic large cell lymphoma (ALCL) |
21 (16) |
5 (11) |
Other |
13 (10) |
7 (16) |
Stage of Disease, n (%)* |
|
|
I/II |
39 (30) |
2 (4) |
III/IV |
91 (70) |
45 (96) |
ECOG Performance Status, n (%) |
|
|
0 |
46 (35) |
20 (43) |
1 |
67 (51) |
22 (47) |
2 |
17 (13) |
4 (9) |
Number of Prior Systemic Therapies |
|
|
Median (Range) |
2 (1, 8) |
3 (1, 6) |
*Stage of disease was reported at time of diagnosis for Study 3 and at time of study entry for Study 4. |
All patients in both studies had received prior systemic therapy for PTCL. In Study 4, a greater percentage of patients had extensive prior radiation and chemotherapy.
Twenty-one patients (16%) in Study 3 and 18 patients (38%) in Study 4 had received prior autologous stem cell transplant and 31 (24%) and 19 (40%) patients,
respectively, had received prior radiation therapy.
Clinical Results
Efficacy outcomes for PTCL patients as determined by the IRC are provided in Table 7 for Study 3. The complete response rate was 15% and overall response rate was
26%. Similar complete response rates were observed by the IRC across the 3 major PTCL subtypes (NOS, AITL, and ALK-1 negative ALCL). Median time to
objective response was 1.8 months (~2 cycles) for the 34 patients who achieved CR, CRu, or PR and median time to CR was 3.5 months (~4 cycles) for the 20 patients
with complete response. The responses in 12 of the 20 patients achieving CR and CRu were known to exceed 11.6 months; the follow-up on the remaining 8 patients
was discontinued prior to 8.5 months.
Table 7. Clinical Results for PTCL Patients
Response Rate |
Study 3
(N=130) |
CR+CRu, n (%)1 |
20 (15.4) [9.7, 22.8]3 |
PR, n (%)2 |
14 (10.8) [6.0, 17.4]3 |
ORR (CR+CRu+PR), n (%)2 |
34 (26.2) [18.8, 34.6]3 |
1 Primary Endpoint.
2 Secondary Endpoint.
3 Two-sided 95% Confidence Interval. |
In a second single-arm clinical study in patients with PTCL who had failed prior therapy (Study 4), patients were treated with ISTODAX at a starting dose of 14 mg/m2
infused over 4 hours on days 1, 8, and 15 every 28 days. Patients could be treated until disease progression at the discretion of the patient and the Investigator. The
percentage of patients achieving CR + CRu in Study 4 was similar to that in Study 3.