|
2013年11月30日，Vifor制药的磷酸盐结合剂Velphoro（sucroferric oxyhydroxide）已获FDA批准上市，用于治疗慢性肾脏病（CKD）透析患者的高磷血症（hyperphosphatemia），以控制其血清磷水平。
There are no empirical data on avoiding drug interactions between Velphoro and most concomitant oral drugs. For oral medications where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy, consider separating the administration of the two drugs. The necessary separation depends upon the absorption characteristics of the medication concomitantly administered, such as the time to reach peak systemic levels and whether the drug is an immediate release or an extended release product. Where possible, consider monitoring for clinical response and/or blood levels of concomitant medications that have a narrow therapeutic range. 8 USE IN SPECIFIC POPULATIONS 8.1 Pregnancy Pregnancy Category B: Reproduction studies have been performed in rats and rabbits at doses up to 16 and 4 times, respectively, the human maximum recommended clinical dose on a body weight basis, and have not revealed evidence of impaired fertility or harm to the fetus due to Velphoro [see Nonclinical Toxicology (13.2)]. However, Velphoro at a dose up to 16 times the maximum clinical dose was associated with an increase in post-implantation loss in pregnant rats. Animal reproduction studies are not always predictive of human response. There are no adequate and well-controlled studies in pregnant women. 8.2 Labor and Delivery No Velphoro treatment-related effects on labor and delivery were seen in animal studies with doses up to 16 times the maximum recommended clinical dose on a body weight basis. The effects of Velphoro on labor and delivery in humans are not known. 8.3 Nursing Mothers Since the absorption of iron from Velphoro is minimal [see Clinical Pharmacology (12.3)], excretion of Velphoro in breast milk is unlikely. 8.4 Pediatric Use The safety and efficacy of Velphoro have not been established in pediatric patients. 8.5 Geriatric Use Of the total number of subjects in two active-controlled clinical studies of Velphoro (N=835), 29.7% (n=248) were 65 and over. No overall differences in safety or effectiveness were observed between these subjects and younger subjects. 10 OVERDOSAGE There are no reports of overdosage with Velphoro in patients. Since the absorption of iron from Velphoro is low [see Clinical Pharmacology (12.3)], the risk of systemic iron toxicity is low. Hypophosphatemia should be treated by standard clinical practice. Velphoro has been studied in doses up to 3,000 mg per day. 11 DESCRIPTION Velphoro chewable tablets are brown, circular, bi-planar, and are embossed with “PA 500” on 1 side. Each tablet of Velphoro contains 500 mg iron (in 2,500 mg sucroferric oxyhydroxide). The Velphoro drug substance is a mixture of polynuclear iron(III)-oxyhydroxide, sucrose, and starches. The active moiety, polynuclear iron(III)-oxyhydroxide, is practically insoluble and cannot be absorbed. The inactive ingredients are woodberry flavor, neohesperidin dihydrochalcone, magnesium stearate, and silica (colloidal, anhydrous). 12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action In the aqueous environment of the GI tract, phosphate binding takes place by ligand exchange between hydroxyl groups and/or water in sucroferric oxyhydroxide and the phosphate in the diet. The bound phosphate is eliminated with feces. Both serum phosphorus levels and calcium-phosphorus product levels are reduced as a consequence of the reduced dietary phosphate absorption. 12.2 Pharmacodynamics In vitro studies have demonstrated a robust phosphate binding capacity of Velphoro over the physiologically relevant pH range of the GI tract (1.2-7.5). The phosphate binding capacity of Velphoro peaked at pH 2.5, resulting in 96% of the available phosphate being adsorbed (phosphorus:iron concentration ratio 0.4:1). 12.3 Pharmacokinetics The active moiety of Velphoro, polynuclear iron(III)-oxyhydroxide (pn-FeOOH), is practically insoluble and therefore not absorbed and not metabolized. Its degradation product, mononuclear iron species, can however be released from the surface of pn-FeOOH and be absorbed. Because of the insolubility and degradation characteristics of Velphoro, no classical pharmacokinetic studies can be carried out. The sucrose and starch components of Velphoro can be digested to glucose and fructose, and maltose and glucose, respectively. These compounds can be absorbed in the blood. One tablet is equivalent to 1.4 g of carbohydrates. The iron uptake from radiolabelled Velphoro drug substance, 2,000 mg in 1 day, was investigated in 16 chronic kidney disease patients (8 pre-dialysis and 8 hemodialysis patients) and 8 healthy volunteers with low iron stores (serum ferritin <100 mcg/L). In healthy subjects, the median uptake of radiolabelled iron in the blood was 0.43% on Day 21. In chronic kidney disease patients, the median uptake was much less, 0.04% on Day 21. Drug Interaction Studies In vitro In vitro interactions were studied in aqueous solutions which mimic the physico-chemical conditions of the gastro-intestinal tract with or without the presence of phosphate (400 mg). The study was conducted at pH 3.0, 5.5 and 8.0 with incubation at 37°C for 6 hours. Interaction with Velphoro was seen with the following drugs: alendronate, doxycycline, levothyroxine, and paricalcitol. The following drugs did not show interaction with Velphoro: ciprofloxacin, enalapril, hydrochlorothiazide, metformin, metoprolol, nifedipine, and quinidine. In vivo Five in vivo drug interaction studies (N=40/study) were conducted with losartan, furosemide, digoxin, omeprazole and warfarin in healthy subjects receiving 1,000 mg Velphoro 3 times a day with meals. Velphoro did not alter the systemic exposure as measured by the area under the curve (AUC) of the tested drugs when co-administered with Velphoro or given 2 hours later. Data from the clinical studies (Study-05A and Study-05B) show that Velphoro does not affect the lipid lowering effects of HMG-CoA reductase inhibitors or the PTH lowering effect of calcitriol. 13 NONCLINICAL TOXICOLOGY 13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenicity studies were performed in mice and rats. In the 2-year carcinogenicity study in mice, animals were given Velphoro by diet at doses of 250, 500 or 1,000 mg/kg/day. Rare but not statistically significant neoplastic adenocarcinomas were seen in the colon of male mice at doses of 500 and 1,000 mg/kg/day. For a 60 kg person, the no-observed-adverse-effect level (NOAEL) of 250 mg/kg/day represents 5 times (on a body weight basis) the maximum recommended clinical dose of 3,000 mg/day. In addition, an increased incidence of epithelial hyperplasia was seen in the colon at all dosage levels (i.e., ≥5 times the maximum recommended clinical dose) and in the cecum at the highest dosage (equivalent to 20 times the maximum recommended clinical dose). The development of adenocarcinoma in the male mice was considered not a genotoxic effect, but the result of chronic local irritation from high amounts of intraluminal Velphoro in the GI tract. In the 2-year rat carcinogenicity study, animals were given Velphoro by diet at doses of 40, 150 or 500 mg/kg/day. No statistically significantly increased incidences of tumors were found, but there were increased incidences in epithelial hyperplasia with or without submucosal inflammation in duodenum, cecum and colon at the dose of 500 mg/kg/day (10 times the maximum recommended clinical dose). Velphoro was not mutagenic, clastogenic or DNA damaging in vitro in the Ames bacterial reverse mutation test, or in the Chinese-hamster fibroblast chromosomal aberration test, or in vivo in the rat Comet assay or peripheral blood micronucleus test. In rats, mating performance and fertility were unaffected by Velphoro at oral doses up to 800 mg/kg/day (16 times the maximum recommended clinical dose). 13.2 Animal Toxicity and/or Pharmacology In pregnant rats given up to 800 mg/kg/day Velphoro by oral gavage from Days 6 to 17 post-mating, no embryo-fetal development toxicity was observed. This dose corresponds to 16 times the maximum recommended clinical dose. In pregnant rabbits given 50, 100 or 200 mg/kg/day Velphoro by oral gavage, from Days 6 to 19 post-mating, the number of fetuses with incomplete/unossified epiphyses and metacarpals/phalanges was increased at the highest dose (corresponding to 4 times the recommended maximum clinical dose). Litter parameters were not adversely affected. In pregnant rats given Velphoro at 100, 280, or 800 mg/kg/day by oral gavage from Day 6 post-mating to lactation Day 20, offspring body weight gain was lower at age 5-13 weeks and neuromuscular function was delayed at the dose of 800 mg/kg/day. This dose represented 16 times the maximum recommended clinical dose. 14 CLINICAL STUDIES The ability of Velphoro to lower serum phosphorus in ESRD patients on dialysis was demonstrated in 2 randomized clinical trials: one 6-week, open-label, active-controlled (sevelamer hydrochloride), dose-finding study; and one 55-week, open-label, active-controlled (sevelamer carbonate), parallel-group, safety and efficacy study. In clinical trials, control of serum phosphorus levels was demonstrated at doses starting from 1,000 mg (2 tablets) per day with treatment effect being observed as early as 1-2 weeks after starting Velphoro. 14.1 Fixed-dose Study In Study-03A, 154 ESRD patients on hemodialysis who were hyperphosphatemic (serum phosphorus >5.5 mg/dL but <7.75 mg/dL) following a 2-week phosphate binder washout period, were randomized to receive Velphoro at 250 mg/day, 1,000 mg/day, 1,500 mg/day, 2,000 mg/day, or 2,500 mg/day or active-control (sevelamer hydrochloride). Velphoro treatment was divided across meals, depending on dose. No dose titration was allowed. Within each of the groups, the serum phosphorus level at the end of treatment was compared to baseline value. Velphoro was shown to be efficacious (p≤0.016) for all doses except 250 mg/day. There were no patient-reported dose limiting treatment-emergent adverse events. Mean changes in iron parameters (ferritin, transferrin saturation (TSAT) and transferrin) and vitamins (A, D, E and K) were generally not clinically meaningful and showed no apparent trends across the treatment groups. Velphoro had a similar GI adverse event profile [see Adverse Reactions (6.1)] to sevelamer hydrochloride, and no dose-dependent trend in GI events was observed. 14.2 Dose Titration Study In Study-05A, 1,054 patients on hemodialysis (N=968) or peritoneal dialysis (N=87) with serum phosphorus ≥6 mg/dL following a 2-4 week phosphate binder washout period, were randomized and treated with either Velphoro, at a starting dose of 1,000 mg/day (N=707), or active-control (sevelamer carbonate, N=348) for 24 weeks. At the end of Week 24, 93 patients on hemodialysis whose serum phosphorus levels were controlled (<5.5 mg/dL) with Velphoro in the first part of the study, were re-randomized to continue treatment with either their Week 24 maintenance dose (N=44 or a non-effective low dose control 250 mg/day, N=49) of Velphoro for a further 3 weeks. At Week 27, a superiority analysis of the Velphoro maintenance dose versus low dose was performed. The maximum dose of Velphoro was 3,000 mg/day (6 tablets/day) and the minimum dose was 1,000 mg/day (2 tablets/day). Velphoro was administered with food and the daily dose was divided across the largest meals of the day. The Velphoro maintenance dose (1,000 to 3,000 mg/day) was statistically significantly superior in sustaining the phosphorus lowering effect in hemodialysis patients at Week 27 (p<0.001) compared with the non-effective low dose control. The results are provided in Table 2. Table 2 Mean (SD) Serum Phosphorus and Change from Baseline to End of Treatment
Notes: BL is Week 24 or latest value available before Week 24 when Week 24 result is missing; End of Treatment is Week 27 value or includes the latest evaluable measurement after Week 24 (i.e., LOCF). BL = Baseline; LOCF = Last observation carried forward; SD = Standard deviation. Following completion of Study-05A, 658 patients (597 on hemodialysis and 61 on peritoneal dialysis) were treated in the 28-week extension study (Study-05B) with either Velphoro (N=391) or sevelamer carbonate (N=267) according to their original randomization. Serum phosphorus levels declined rapidly during the first few weeks of treatment and remained relatively constant thereafter. The phosphorus lowering effect of Velphoro was consistently maintained through 12 months of treatment (shown in Figure 1). Age, gender, race, or dialysis modality did not affect the efficacy of Velphoro. Serum iron level increases from baseline were not clinically meaningful and did not differ significantly compared to the active control. There was no evidence of accumulation of iron during one year treatment. There were no clinically meaningful changes for vitamins (A, D, E and K) with Velphoro.
| ||||||||||||||||||||||||||||||
