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SOMAVERT® (pegvisomant) Clinical Studies

14 CLINICAL STUDIES

A total of one hundred twelve patients (63 men and 49 women) with acromegaly participated in a 12-week, randomized, double-blind, multi-center study comparing placebo and SOMAVERT. The mean ±SD age was 48±14 years, and the mean duration of acromegaly was 8±8 years. Ninety three had undergone previous pituitary surgery, of which 57 had also been treated with conventional radiation therapy. Six patients had undergone irradiation without surgery, nine had received only drug therapy, and four had received no previous therapy. At study start, the mean ± SD time since the subjects' last surgery and/or irradiation therapy, respectively, was 6.8 ± 0.93 years (n=63) and 5.6 ± 0.57 years (n=93).

Subjects were qualified for enrollment if their serum IGF-I, drawn after the required drug washout period, was ≥1.3 times the upper limit of the age-adjusted normal range. They were randomly assigned at the baseline visit to one of four treatment groups: placebo (n=32), 10 mg/day (n=26), 15 mg/day (n= 26), or 20 mg/day (n=28) of SOMAVERT subcutaneouslyIGF-I. The primary efficacy endpoint was IGF-I percent change in IGF-I concentrations from baseline to week 12. The three groups that received SOMAVERT showed statistically significant (p<0.01) reductions in serum levels of IGF-I compared with the placebo group (Table 4).

Table 4. Mean Percent Change from Baseline in IGF-I at Week 12 for Intent-to-Treat Population
Placebo
n=31
SOMAVERT
10 mg/day
n=26
15 mg/day
n=26
20 mg/day
n=28
*
P<0.01; n=number of patients; SD = standard deviation
Mean baseline IGF-I (ng/ml) (SD) 670 (288) 627 (251) 649 (293) 732 (205)
Mean percent change from baseline in IGF-I (SD) -4.0 (17)
-27 (28)
-48 (26)
-63 (21)
SOMAVERT minus Placebo
(95% CI for treatment difference)
-23*
(-35, -11)
-44*
(-56, -33)
-59*
(-68, -49)

There were also reductions in serum levels of free IGF-I, IGFBP-3, and ALS compared with placebo at all post-baseline visits (Figure 1).

Figure 1. Effects of SOMAVERT on Serum Markers (Mean ± Standard Error)
Figure 1

After 12 weeks of treatment, the following percentages of patients had normalized IGF-1 (Figure 2):

Figure 2. Percent of Patients Whose IGF-I Levels Normalized at Week 12
Figure 2

Table 5 shows the effect of treatment with SOMAVERT on ring size (standard jeweler's sizes converted to a numeric score ranging from 1 to 63), and on signs and symptoms of acromegaly. Each individual score for a sign or symptom of acromegaly (for soft-tissue swelling, arthralgia, headache, perspiration and fatigue) was based on a nine-point ordinal rating scale (0 = absent and 8 = severe and incapacitating), and the total score for signs or symptoms of acromegaly was derived from the sum of the individual scores. Mean baseline scores were as follows: ring size = 47.1; total signs and symptoms = 15.2; soft tissue swelling = 2.5; arthralgia = 3.2; headache = 2.4; perspiration = 3.3; and fatigue = 3.7.

Table 5. Mean Change from Baseline (SD) at Week 12 for Ring Size and Signs and Symptoms of Acromegaly
Placebo
n=30
SOMAVERT
10 mg/day
n=26
15 mg/day
n=24–25
20 mg/day
n=26–27
Ring size -0.1 (2.3) -0.8 (1.6) -1.9 (2.0) -2.5 (3.3)
Total score for signs and symptoms of acromegaly 1.3 (6.0) -2.5 (4.3) -4.4 (5.9) -4.7 (4.7)
  Soft-tissue swelling 0.3 (2.3) -0.7 (1.6) -1.2 (2.3) -1.3 (1.3)
  Arthralgia 0.1 (1.8) -0.3 (1.8) -0.5 (2.5) -0.4 (2.1)
  Headache 0.1 (1.7) -0.4 (1.6) -0.3 (1.4) -0.3 (2.0)
  Perspiration 0.1 (1.7) -0.6 (1.6) -1.1 (1.3) -1.7 (1.6)
  Fatigue 0.7 (1.5) -0.5 (1.4) -1.3 (1.7) -1.0 (1.6)

Serum growth hormone (GH) concentrations, as measured by research assays using antibodies that do not cross-react with pegvisomant, rose within two weeks of beginning treatment with SOMAVERT. The largest increase in GH concentration was seen in patients treated with doses of SOMAVERT 20 mg/day. This effect is presumably the result of diminished inhibition of GH secretion as IGF-I levels fall. As shown in Figure 3, when patients with acromegaly were given a loading dose of SOMAVERT followed by a fixed daily dose, the rise in GH was inversely proportional to the fall in IGF-I and generally stabilized by week 2. Serum GH concentrations remained stable in patients treated with SOMAVERT for the average of 43 weeks (range, 0–82 weeks).

Figure 3. Percent Change in Serum GH and IGF-I Concentrations
Figure 3

In the open-label extension to the clinical study, 109 subjects (including 6 new patients) with mean treatment exposure of 42.6 weeks (range 1 day – 82 weeks), 93 (85.3%) subjects had an adverse event, 16 (14.7%) had an SAE, and 4 (3.7%) discontinued due to an AE (headaches, elevated liver function tests, pancreatic cancer, and weight gain). A total of 100 (92.6%) of the 108 subjects with available IGF-I data had a normal IGF-I concentration at any visit during the study.

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