Clinical Pharmacology for Gattex
Mechanism Of Action
Teduglutide is an analog of naturally occurring human glucagon-like peptide-2 (GLP-2), a peptide secreted by L-cells of the distal intestine. GLP-2 is known to increase intestinal and portal blood flow and inhibit gastric acid secretion. Teduglutide binds to the glucagon-like peptide-2 receptors located in intestinal subpopulations of enteroendocrine cells, subepithelial myofibroblasts and enteric neurons of the submucosal and myenteric plexus. Activation of these receptors results in the local release of multiple mediators including insulin-like growth factor (IGF)-1, nitric oxide and keratinocyte growth factor (KGF).
Pharmacodynamics
Intestinal Fluid Absorption
The ability of GATTEX to improve intestinal absorption was studied in 17 adult subjects with Short Bowel Syndrome (N=2-3 per dose group) using daily doses of 0.03, 0.1, 0.15 mg/kg (doses ranging from 0.6 to 3 times the recommended dose) in a 21-day, open-label, multicenter, dose-ranging study. All subcutaneous (abdomen) doses studied, except 0.03 mg/kg once daily, resulted in enhanced gastrointestinal fluid (wet weight) absorption of approximately 750 to 1000 mL/day, and increased villus height and crypt depth of the intestinal mucosa.
Cardiac Electrophysiology
At a dose 5 times the recommended dose, GATTEX did not prolong the QT interval to any clinically relevant extent.
Pharmacokinetics
Absorption
In healthy subjects, GATTEX administered subcutaneously had an absolute bioavailability of 88% and reached maximum plasma teduglutide concentrations at 3 to 5 hours after administration. Following a 0.05 mg/kg subcutaneous dose in SBS subjects, the median peak teduglutide concentration (Cmax) was 36 ng/mL and the median area under the curve at steady state (AUCtau) was 0.15 μg•hr/mL. No accumulation of teduglutide was observed following repeated subcutaneous administrations.
The Cmax and AUC of teduglutide was dose proportional over the dose range of 0.05 to 0.4 mg/kg (up to 8 times the recommended dose of GATTEX).
Distribution
In healthy subjects, teduglutide has a volume of distribution (103 mL/kg) similar to blood volume.
Elimination
Metabolism
The metabolic pathway of teduglutide was not investigated in humans. However, teduglutide is expected to be degraded into small peptides and amino acids via catabolic pathways, similar to the catabolism of endogenous GLP-2.
Excretion
In healthy subjects, teduglutide plasma clearance was approximately 123 mL/hr/kg which is similar to the GFR suggesting that teduglutide is primarily cleared by the kidney. Teduglutide has a mean terminal half-life (t1/2) of approximately 2 hours in healthy subjects and 1.3 hours in SBS subjects.
Use In Specific Populations
Geriatric Patients
No differences were observed between healthy subjects younger than 65 years and those older than 65 years. Experience in subjects 75 years and above is limited.
Pediatric Patients
Following subcutaneous administration, similar steady state Cmax of teduglutide across age groups was demonstrated by population pharmacokinetics modeling (see Table 2). However, lower AUC was seen in pediatric patients 1 to 17 years of age as compared with adults and increases with increasing age.
Table 2: Teduglutide Pharmacokinetic Parameters Following Subcutaneous Dosing of GATTEX 0.05 mg/kg by Age Groups
| Age |
Parameters (Mean ± SD) |
| Cmax, ss (ng/mL) |
AUCss (ng•h/mL) |
CL/F (L/h) |
t1/2 (h) |
| 12 to 17 years (n=3) |
29.7 ± 8.4 |
154 ± 17.6 |
13.0 ± 2.3 |
1.0 ± 0.01 |
| 1 to 11 years (n=37) |
33.5 ± 11.5 |
128 ± 56.7 |
7.45 ± 2.1 |
0.7 ± 0.2 |
Male And Female Patients
No clinically relevant gender differences were observed.
Patients With Renal Impairment
In adult subjects with moderate to severe renal impairment or end stage renal disease (ESRD) (creatinine clearance <60 mL/min), the Cmax and AUC0-inf of teduglutide increased with the degree of renal impairment following a single subcutaneous dose of 10 mg GATTEX. Teduglutide exposure increased by a factor of 1.6, 1.4, and 2.1 (Cmax) and 1.5, 1.7, and 2.6 (AUC0-inf) in subjects with moderate, severe renal impairment and ESRD, respectively, compared to healthy subjects [see DOSAGE AND ADMINISTRATION, Use In Specific Populations].
Patients With Hepatic Impairment
Subjects with moderate hepatic impairment (Child-Pugh Class B) had an approximately 10 to 15% lower teduglutide Cmax and AUC compared to healthy matched control subjects after a single subcutaneous dose of 20 mg GATTEX. This reduction in teduglutide exposure is not thought to be clinically meaningful. GATTEX was not studied in subjects with severe hepatic impairment (Child-Pugh Class C).
Drug Interaction Studies
Clinical interaction studies were not performed. No inhibition or induction of the cytochrome P450 enzyme system has been observed based on in vitro studies although the relevance of in vitro studies to an in vivo setting is unknown.
Immunogenicity
The observed incidence of anti-drug antibodies is highly dependent on the sensitivity and specificity of the assay. Differences in assay methods preclude meaningful comparisons of the incidence of anti-drug antibodies in the studies described below with the incidence of anti-drug antibodies in other studies, including those of GATTEX or of other teduglutide products.
Adults
Based on integrated data from two studies in adults with SBS (a 6-month randomized placebo-controlled study, followed by a 24-month open-label study), the development of anti-teduglutide antibodies in patients who received subcutaneous administration of 0.05 mg/kg GATTEX once daily was 3% (2/60) at Month 3, 17% (13/77) at Month 6, 24% (16/67) at Month 12, 33% (11/33) at Month 24, and 48% (14/29) at Month 30. Anti-teduglutide antibodies were cross-reactive to native glucagon-like peptide (GLP-2) in 5 of the 6 patients (83%) who had anti-teduglutide antibodies and were tested for cross-reactivity. In the same two studies, a total of 36 patients were tested for neutralizing antibodies: one patient developed borderline positive neutralizing antibody responses at month 24 of the extension study. The antibody formation has not been associated with clinically relevant safety findings, reduced efficacy or changed pharmacokinetics of GATTEX.
Pediatric Patients 1 Year To Less Than 17 Years Of Age
In pediatric patients who received subcutaneous administration of 0.05 mg/kg GATTEX once daily for 24 weeks, the rate of anti-teduglutide antibody formation at Month 6 was 19% (5/26) and was similar to the rate of antibody formation in adult patients (17%). Of the 5 pediatric patients who had developed antibodies to teduglutide at Month 6, 2 patients had neutralizing antibodies. However, with the longer duration of treatment, the rate of anti-teduglutide formation at Month 12 was higher in pediatric patients with 54% (14/26), compared to that of adults (24%). Of the 14 pediatric patients who had developed antibodies to teduglutide at Month 12, 1 patient had neutralizing antibodies.
Among the small number of pediatric patients who developed anti-teduglutide antibodies, no association with adverse events or lack of efficacy was observed.
Clinical Studies
Treatment Of SBS In Adults
Study 1 (Placebo-Controlled) And Study 2 (Open-Label Extension Of Study 1)
Study 1 (CL0600-020, NCT00798967)
The efficacy, safety, and tolerability of GATTEX was evaluated in a randomized, double-blind, placebo-controlled, parallel-group, multi-national, multicenter clinical study (Study 1) in adults with SBS who were dependent on parenteral nutrition/intravenous (PN/I.V.) support for at least 12 months and required PN at least 3 times per week. For 8 weeks (or less) prior to randomization, investigators optimized the PN/I.V. volume of all patients. Optimization was followed by a 4-week to 8-week period of fluid stabilization. Patients then were randomized (1:1) to placebo (n=43) or GATTEX 0.05 mg/kg/day (n=43). Study treatment was administered subcutaneously once daily for 24 weeks. PN/I.V. volume adjustments (up to 30% decrease) and clinical assessments were made at 2, 4, 8, 12, 20, and 24 weeks.
The primary efficacy endpoint was based on a clinical response, defined as a patient achieving at least 20% reduction in weekly PN/I.V. volume from Baseline (immediately before randomization) to both Weeks 20 and 24.
The mean age of patients was 50 years. Mean duration of PN/I.V. dependency prior to enrollment was 6 years (range 1 to 26 years). The most common reasons for intestinal resection leading to SBS were vascular disease (34%, 29/85), Crohn’s Disease (21%, 18/85), and “other” (21%, 18/85). Stoma was present in 45% (38/85) of patients, and the most common type was jejunostomy/ileostomy (82%, 31/38). The mean length of remaining small intestine was 77.3±64.4 cm (range: 5 to 343 cm). The colon was not in continuity in 44% (37/85) patients. At baseline, the mean (± SD) prescribed days per week for PN/I.V. infusion was 5.73 (±1.59) days.
The percentages of treatment group responders were compared in the intent-to-treat population of this study which was defined as all randomized patients. Sixty-three percent (27/43) of GATTEX-treated patients versus 30% (13/43) of placebo-treated patients were considered responders (p=0.002).
At Week 24, the mean reduction in weekly PN/I.V. volume was 4.4 Liters for GATTEX-treated patients (from pre-treatment baseline of 12.9 Liters) versus 2.3 Liters for placebo-treated patients (from pre-treatment baseline of 13.2 Liters/week) (p<0.001).
Twenty-one patients on GATTEX (54%) versus 9 on placebo (23%) achieved at least a one-day reduction in PN/I.V. support.
The mean changes from Baseline in PN/I.V. volume by visit are shown in Figure 2.
Figure 2: Change (±95% CI) in PN/I.V. volume (L/week)
Study 2 (CL0600-021, NCT00930644)
Study 2 was a 2-year open-label extension of Study 1 in which 88 patients received GATTEX 0.05 mg/kg/day. Ninety-seven percent (76/78) of patients who completed Study 1 elected to enroll in Study 2 (37 received GATTEX; 39 received Placebo). An additional 12 patients entered Study 2, who had been optimized and stabilized but not randomized in Study 1 because of closed enrollment.
30 months exposure
Thirty GATTEX patients completed a total duration of 30 months (Study 1 followed by Study 2 treatment). Of these, 28 patients (93%) achieved a 20% or greater reduction of parenteral support (PS). Of responders in Study 1 who had completed 2 additional years of continuous treatment with GATTEX, 96% (21/22) sustained their response to GATTEX. The mean reduction in PN/I.V. (n=30) was 7.55 L/week (a 66% reduction from baseline). Ten patients were weaned off their PN/I.V. support while on GATTEX treatment for 30 months. Patients were maintained on GATTEX even if no longer requiring PN/I.V. support. These 10 patients had required PN/I.V. support for 1.2 to 15.5 years, and prior to GATTEX had required between 3.5 L/week and 13.4 L/week of PN/I.V. support. At the end of study, 21 (70%), 18 (60%) and 18 (60%) of the 30 completers achieved a reduction of 1, 2, or 3 days per week in PN/I.V. support, respectively.
24 months exposure
Of the 39 placebo-treated patients from Study 1 entering Study 2, 29 completed 24 months of treatment with GATTEX. The mean reduction in PN/I.V. was 3.11 L/week (an additional 28.3% reduction) from the start of Study 2. Sixteen (55%) of the 29 completers achieved a 20% or greater reduction of PS. At the end of the study, 14 (48%), 7 (24%) and 5 (17%) achieved a reduction of 1, 2, or 3 days per week in PN/I.V. support, respectively. Two patients were weaned off their PN/I.V. support while on GATTEX. Of the 12 patients entering Study 2 directly, 6 completed 24 months of treatment with GATTEX. Similar effects were seen. One of the six patients was weaned off their PN/I.V. support while on GATTEX.
Study 3 (Placebo-Controlled) And Study 4 (Blinded Uncontrolled Extension Of Study 3)
Study 3 (CL0600-004, NCT00081458)
Study 3 was a randomized, double-blind, placebo-controlled, three parallel-group, multinational study in adults with SBS who were dependent on parenteral nutrition/intravenous (PN/I.V.)
support for at least 12 months and required PN at least 3 times per week. After a period of optimization and stabilization similar to Study 1, patients were randomized to receive 24 weeks of one of the following treatment regimens: GATTEX 0.05 mg/kg/day (n=35), GATTEX 0.1 mg/kg/day (twice the recommended dose) (n=33), or placebo (n=16). GATTEX 0.1 mg/kg/day is not a recommended dosage [see DOSAGE AND ADMINISTRATION]. The treatment groups were compared using the intent-to-treat population of this study which was defined as all randomized patients who were administered at least one dose of study drug. This population contained one less patient in the 0.1 mg/kg/day dose group hence n=32 in this group for all analyses. The primary efficacy endpoint was a graded categorical score that did not achieve statistical significance for the high dose. Further evaluation of PN/I.V. volume reduction using the endpoint of response (defined as at least 20% reduction in PN/I.V. fluid from Baseline to Weeks 20 and 24) showed that 46% of patients on GATTEX 0.05 mg/kg/day responded versus 6% on placebo. Patients on GATTEX in both dose groups experienced a 2.5 L/week reduction in PS requirements versus 0.9 L/week for placebo at 24 weeks. Two patients in the GATTEX 0.05 mg/kg/day dose group were weaned off PS by Week 24.
Study 4 (CL0600-005, NCT00172185)
Study 4 was a blinded, uncontrolled extension of Study 3, in which 65 patients from Study 3 received GATTEX for up to an additional 28 weeks of treatment. Of responders in Study 3 who entered Study 4, 75% sustained response on GATTEX after one year of treatment. In the GATTEX 0.05 mg/kg/day dose group, a 20% or greater reduction of PS was achieved in 68% (17/25) of patients. The mean reduction of weekly PN/I.V. volume was 4.9 L/week (52% reduction from baseline) after one year of continuous GATTEX treatment. The patients who had been completely weaned off PN/I.V. support in Study 3 remained off PS through Study 4. During Study 4, an additional patient from Study 3 was weaned off PS.
Treatment Of SBS In Pediatric Patients
Study 5 (TED-C14-006, NCT02682381)
Study 5 was a 24-week, multicenter study conducted in 59 pediatric patients aged 1 year through 17 years with SBS who were dependent on PS. Patients chose whether to receive GATTEX or standard of care (SOC). Patients who chose to receive GATTEX treatment were subsequently randomized in a double-blind manner to 0.025 mg/kg/day (n=24) or 0.05 mg/kg/day (n=26), while 9 patients enrolled in the SOC arm. Randomization to the GATTEX dose groups was stratified by age.
Patients treated with 0.05 mg/kg had a mean age of 6 years at baseline. The most common reasons for intestinal resection leading to SBS were gastroschisis (54%, 14/26), midgut volvulus (23%, 6/26), and necrotizing enterocolitis (12%, 3/26). Stoma was present in 19% (5/26) of patients, and the most common type was jejunostomy (80%, 4/5). The mean length of remaining small intestine was 47 (±28) cm (range: 9 to 120 cm). In the 25 patients who had remaining colon, the colon was in continuity in 22 patients. At baseline, the mean PS volume was 60 (±29) mL/kg/day (range: 24 to 133 mL/kg/day) [8 (±4) L/week (range: 3 to 19 L/week)] and mean PS infusion time was 7 (±1) days/week (range: 5 to 7 days/week) and 11 (±3) hours/day (range: 7 to 20 hours/day).
Results described in Table 3 correspond to the recommended GATTEX dosage of 0.05 mg/kg subcutaneously once daily.
Table 3: Summary of Efficacy Endpoints at Week 24* for Study 5 – Patients treated with GATTEX 0.05 mg/kg/day (N = 26)
| Efficacy Endpoints |
Results |
| Reduction in PS volume of at least 20%, n/N (%) |
18/26 (69%) |
| Achieved enteral autonomy, n/N (%) |
3/26 (12%) |
| Reduction in PS infusion of ≥1 day/week, n/N (%) |
10/26 (38%) |
| Change in PS volume from baseline (mL/kg/day), mean |
-23 (18) mL/kg/day |
| (SD) and [mean% (SD)] |
[-42% (29%)] |
| *Results based on patient diary data, ITT population |
Study 6 (SHP633-304, NCT02954458)
Study 6 was a prospective, open-label, long-term extension study of pediatric patients who completed Study 5. In the extension study, patients received additional treatment with GATTEX 0.05 mg/kg subcutaneously once daily if they deteriorated or stopped improving after discontinuation of prior GATTEX treatment. Of the 15 patients who initially responded in Study 5 and enrolled in Study 6, 13 patients (87%) required additional treatment with GATTEX. Efficacy results at the end of the first 24-week treatment period in Study 6 (total treatment for a mean of 40 weeks) were similar to those achieved at the end of 24 weeks treatment in Study 5. One additional patient treated with 0.05 mg/kg in Study 5 eventually achieved enteral autonomy during follow-up in Study 6.