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Mechanism Of Action
Regorafenib is a small molecule inhibitor of multiple membrane-bound and intracellular kinases involved in normal cellular functions and in pathologic processes such as oncogenesis, tumor angiogenesis, and maintenance of the tumor microenvironment. In in vitro biochemical or cellular assays, regorafenib or its major human active metabolites M-2 and M-5 inhibited the activity of RET, VEGFR1, VEGFR2, VEGFR3, KIT, PDGFR-alpha, PDGFR-beta, FGFR1, FGFR2, TIE2, DDR2, TrkA, Eph2A, RAF-1, BRAF, BRAF V600E, SAPK2, PTK5, and Abl at concentrations of regorafenib that have been achieved clinically. In in vivo models, regorafenib demonstrated anti-angiogenic activity in a rat tumor model, and inhibition of tumor growth as well as anti-metastatic activity in several mouse xenograft models including some for human colorectal carcinoma.
The effect of multiple doses of Stivarga (160 mg once daily for 21 days) on the QTc interval was evaluated in an openlabel, single-arm study in 25 patients with advanced solid tumors. No large changes in the mean QTc interval (i.e., > 20 msec) were detected in the study.
Following a single 160 mg dose of Stivarga in patients with advanced solid tumors, regorafenib reaches a geometric mean peak plasma level (Cmax) of 2.5 μg/mL at a median time of 4 hours and a geometric mean area under the plasma concentration vs. time curve (AUC) of 70.4 μg*h/mL. The AUC of regorafenib at steady-state increases less than dose proportionally at doses greater than 60 mg. At steady-state, regorafenib reaches a geometric mean Cmax of 3.9 μg/mL and a geometric mean AUC of 58.3 μg*h/mL. The coefficient of variation of AUC and Cmax is between 35% and 44%.
The mean relative bioavailability of tablets compared to an oral solution is 69% to 83%.
In a food-effect study, 24 healthy men received a single 160 mg dose of Stivarga on three separate occasions: under a fasted state, with a high-fat meal and with a low-fat meal. A high-fat meal (945 calories and 54.6 g fat) increased the mean AUC of regorafenib by 48% and decreased the mean AUC of the M-2 and M-5 metabolites by 20% and 51%, respectively, as compared to the fasted state. A low-fat meal (319 calories and 8.2 g fat) increased the mean AUC of regorafenib, M-2 and M-5 by 36%, 40% and 23%, respectively as compared to fasted conditions. Stivarga was administered with a low-fat meal in Studies 1 and 2 [see DOSAGE AND ADMINISTRATION, Clinical Studies].
Regorafenib undergoes enterohepatic circulation with multiple plasma concentration peaks observed across the 24-hour dosing interval. Regorafenib is highly bound (99.5%) to human plasma proteins.
Following a single 160 mg oral dose of Stivarga, the geometric mean (minimum to maximum) elimination half-lives for regorafenib and the M-2 metabolite in plasma are 28 hours (14 to 58 hours) and 25 hours (14 to 32 hours), respectively. M-5 has a longer mean (minimum to maximum) elimination half-life of 51 hours (32 to 70 hours).
Regorafenib is metabolized by CYP3A4 and UGT1A9. The main circulating metabolites of regorafenib measured at steady-state in human plasma are M-2 (N-oxide) and M-5 (N-oxide and N-desmethyl). Both metabolites have similar in vitro pharmacological activity and steady-state concentrations as regorafenib. M-2 and M-5 are highly protein bound (99.8% and 99.95%, respectively).
Approximately 71% of a radiolabeled dose was excreted in feces (47% as parent compound, 24% as metabolites) and 19% of the dose was excreted in urine (17% as glucuronides) within 12 days after administration of a radiolabeled oral solution at a dose of 120 mg.
Age, sex, race and weight had no clinically meaningful effect on the pharmacokinetics of regorafenib.
The pharmacokinetics of regorafenib, M-2, and M-5 was evaluated in 14 patients with hepatocellular carcinoma (HCC) and mild hepatic impairment (Child-Pugh A); 4 patients with HCC and moderate hepatic impairment (Child-Pugh B); and 10 patients with solid tumors and normal hepatic function after the administration of a single 100 mg dose of Stivarga. No clinically important differences in the mean exposure of regorafenib, M-2, or M-5 were observed in patients with mild or moderate hepatic impairment compared to the patients with normal hepatic function. The pharmacokinetics of regorafenib has not been studied in patients with severe hepatic impairment (Child-Pugh C).
The pharmacokinetics of regorafenib, M-2, and M-5 was evaluated in 10 patients with mild renal impairment (CLcr 60-89 mL/min) and 18 patients with normal renal function following the administration of Stivarga at a dose of 160 mg daily for 21 days. No differences in the mean steady-state exposure of regorafenib, M-2, or M-5 were observed in patients with mild renal impairment compared to patients with normal renal function. Limited pharmacokinetic data were available from patients with moderate renal impairment (CLcr 30-59 mL/min). The pharmacokinetics of regorafenib has not been studied in patients with severe renal impairment or end-stage renal disease.
Drug Interaction Studies
Effect of Regorafenib on Cytochrome P450 Substrates: In vitro studies suggested that regorafenib is an inhibitor of CYP2C8, CYP2C9, CYP2B6, CYP3A4 and CYP2C19; M-2 is an inhibitor of CYP2C9, CYP2C8, CYP3A4 and CYP2D6, and M-5 is an inhibitor of CYP2C8. In vitro studies suggested that regorafenib is not an inducer of CYP1A2, CYP2B6, CYP2C19, and CYP3A4 enzyme activity.
Patients with advanced solid tumors received single oral doses of CYP substrates, 2 mg of midazolam (CYP3A4), 40 mg of omeprazole (CYP2C19) and 10 mg of warfarin (CYP2C9) or 4 mg of rosiglitazone (CYP2C8) one week before and two weeks after Stivarga at a dose of 160 mg once daily. No clinically meaningful effect was observed in the mean AUC of rosiglitazone (N=12) or the mean omeprazole (N=11) plasma concentrations measured 6 hours after dosing or the mean AUC of midazolam (N=15). The mean AUC of warfarin (N=8) increased by 25% [see WARNINGS AND PRECAUTIONS].
Effect of CYP3A4 Strong Inducers on Regorafenib: Twenty-two healthy men received a single 160 mg dose of Stivarga alone and then 7 days after starting rifampin. Rifampin, a strong CYP3A4 inducer, was administered at a dose of 600 mg daily for 9 days. The mean AUC of regorafenib decreased by 50% and mean AUC of M-5 increased by 264%. No change in the mean AUC of M-2 was observed [see DRUG INTERACTIONS].
Effect of CYP3A4 Strong Inhibitors on Regorafenib: Eighteen healthy men received a single 160 mg dose of Stivarga alone and then 5 days after starting ketoconazole. Ketoconazole, a strong CYP3A4 inhibitor, was administered at a dose of 400 mg daily for 18 days. The mean AUC of regorafenib increased by 33% and the mean AUC of M-2 and M-5 both decreased by 93% [see DRUG INTERACTIONS].
Effect of Neomycin on Regorafenib: Twenty-seven healthy men received a single 160 mg dose of Stivarga and then 5 days after starting neomycin. Neomycin, a non-absorbable antibiotic, was administered at a dose of 1 gram three times daily for 5 days. No clinically meaningful effect on the mean AUC of regorafenib was observed; however, the mean AUC of M-2 decreased by 76% and the mean AUC of M-5 decreased by 86%. The decreased exposure of M-2 and M-5 may result in a decreased efficacy of Stivarga. The effects of other antibiotics on the exposure of regorafenib and its active metabolites have not been studied.
Effect of Regorafenib on UGT1A1 Substrates: In vitro studies showed that regorafenib, M-2, and M-5 competitively inhibit UGT1A9 and UGT1A1 at therapeutically relevant concentrations. Eleven patients received irinotecan-containing combination chemotherapy with Stivarga at a dose of 160 mg. The mean AUC of irinotecan increased by 28% and the mean AUC of SN-38 increased by 44% when irinotecan was administered 5 days after the last of 7 daily doses of Stivarga.
In vitro screening of transporters: In vitro data suggested that regorafenib, M-2, and M-5 are inhibitors of breast cancer resistance protein (BCRP) and that regorafenib and M-2 are inhibitors of multidrug resistance protein 1 (MDR1).
Animal Toxicology And/Or Pharmacology
In a chronic 26-week repeat dose study in rats there was a dose-dependent increase in the finding of thickening of the atrioventricular valve. At a dose that resulted in an exposure of approximately 12% of the human exposure at the recommended dose, this finding was present in half of the examined animals.
The clinical efficacy and safety of Stivarga were evaluated in an international, multicenter, randomized (2:1), doubleblind, placebo-controlled trial (Study 1) in 760 patients with previously-treated metastatic colorectal cancer. The major efficacy outcome measure was overall survival (OS); additional efficacy outcome measures included progression-free survival (PFS) and objective tumor response rate.
Patients were randomized to receive 160 mg regorafenib orally once daily (N=505) plus best supportive care (BSC) or placebo (N=255) plus BSC for the first 21 days of each 28-day cycle. Stivarga was administered with a low-fat breakfast that contains less than 30% fat [see DOSAGE AND ADMINISTRATION, CLINICAL PHARMACOLOGY]. Treatment continued until disease progression or unacceptable toxicity.
Baseline demographics were: median age 61 years, 61% men, 78% White, and all patients had an ECOG performance status of 0 or 1. The primary sites of disease were colon (65%), rectum (29%), or both (6%). History of KRAS evaluation was reported for 729 (96%) patients; 430 (59%) of these patients were reported to have KRAS mutation. The median number of prior lines of therapy for metastatic disease was 3. All patients received prior treatment with fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy, and with bevacizumab. All but one patient with KRAS mutationnegative tumors received panitumumab or cetuximab.
The addition of Stivarga to BSC resulted in a statistically significant improvement in survival compared to placebo plus BSC (see Table 5 and Figure 1).
Table 5: Efficacy Results from Study 1
|Number of Deaths (%)||275 (55%)||157 (62%)|
|Median Overall Survival (months)||6.4||5.0|
|95% CI*||(5.8, 7.3)||(4.4, 5.8)|
|HR (95% CI)||0.77 (0.64, 0.94)|
|Stratified log-rank test p-valuea,b||0.0102|
|Number of Deaths or Progressions (%)||417 (83%)||231 (91%)|
|Median Progression-Free Survival (months)||2.0||1.7|
|95% CI||(1.9, 2.3)||(1.7, 1.8)|
|HR (95% CI)||0.49 (0.42, 0.58)|
|Stratified log-rank test p-value a||< 0.0001|
|Overall Response Rate|
|Overall Response, N (%)||5 (1%)||1 (0.4%)|
|95% CI||0.3%, 2.3%||0%, 2.2%|
|a Stratified by geographic region and time
from diagnosis of metastatic disease.
b Crossed the Oâ€™Brien-Fleming boundary (two-sided p-value < 0.018) at second interim analysis.
* CI=confidence interval
Figure 1: Kaplan-Meier Curves of Overall Survival
Gastrointestinal Stromal Tumors
The efficacy and safety of Stivarga were evaluated in an international, multicenter, randomized (2:1), double-blind, placebo-controlled trial (Study 2) in 199 patients with unresectable, locally advanced or metastatic gastrointestinal stromal tumor (GIST), who had been previously treated with imatinib mesylate and sunitinib malate. Randomization was stratified by line of therapy (third vs. four or more) and geographic region (Asia vs. rest of the world).
The major efficacy outcome measure of Study 2 was progression-free survival (PFS) based on disease assessment by independent radiological review using modified RECIST 1.1 criteria, in which lymph nodes and bone lesions were not target lesions and progressively growing new tumor nodule within a pre-existing tumor mass was progression. The key secondary outcome measure was overall survival.
Patients were randomized to receive 160 mg regorafenib orally once daily (N=133) plus best supportive care (BSC) or placebo (N=66) plus BSC for the first 21 days of each 28-day cycle. Treatment continued until disease progression or unacceptable toxicity. In Study 2, the median age of patients was 60 years, 64% were men, 68% were White, and all patients had baseline ECOG performance status of 0 (55%) or 1 (45%). At the time of disease progression as assessed by central review, the study blind was broken and all patients were offered the opportunity to take Stivarga at the investigatorâ€™s discretion. Fifty-six (85%) patients randomized to placebo and 41 (31%) patients randomized to Stivarga received open-label Stivarga.
A statistically significant improvement in PFS was demonstrated among patients treated with Stivarga compared to placebo (see Table 6 and Figure 2). There was no statistically significant difference in overall survival at the time of the planned interim analysis based on 29% of the total events for the final analysis.
Table 6: Efficacy Results for Study 2
|Number of Deaths or Progressions (%)||82 (62%)||63 (96%)|
|Median Progression-Free Survival (months)||4.8||0.9|
|95% CI||(3.9, 5.7)||(0.9, 1.1)|
|HR (95% CI)||0.27 (0.]||[9, 0.39)|
|Stratified log-rank test p-value a||< 0.0001|
|Number of Deaths (%)||29 (22%)||17 (26%)|
|Median Overall Survival (months)||NRb||NRb|
|HR (95% CI)||0.77 (0.4||12, 1.41)|
|Stratified log-rank test p-valuea,b||0.2|
|a Stratified by line of treatment and geographical
b NR: Not reached.
Figure 2: Kaplan-Meier Curves of Progression-Free
Survival for Study 2
Last reviewed on RxList: 6/28/2016
This monograph has been modified to include the generic and brand name in many instances.
Additional Stivarga Information
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