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Ettinger MP, Littlejohn TW, Schwartz SL, et al. Recombinant Variant of Ciliary Neurotrophic Factor for Weight Loss in Obese Adults: A Randomized, Dose-Ranging Study. JAMA. 2003;289(14):1826–1832. doi:10.1001/jama.289.14.1826
Author Affiliations: Radiant Research, Stuart, Fla (Dr Ettinger); Piedmont Medical Research Associates, Winston-Salem, NC (Dr Littlejohn); Diabetes & Glandular Disease Clinic, San Antonio, Tex (Dr Schwartz); Radiant Research, San Diego, Calif (Dr Weiss); Tampa Medical Group Research, Tampa, Fla (Dr McIlwain); St Luke's-Roosevelt Hospital, New York, NY (Drs Heymsfield and Heshka); Pennington Biomedical Research Center, Baton Rouge, La (Dr Bray); Celeris Corp, Rockville, Md (Dr Heyman); Regeneron Pharmaceuticals Inc, Tarrytown, NY (Drs Roberts and Guler and Mss Stambler and Vicary).
Context Obese individuals tend to resist the weight-regulating effects of exogenously
administered leptin. A genetically engineered recombinant human variant ciliary
neurotrophic factor (rhvCNTF) that signals through leptinlike pathways in
the hypothalamus has been shown to bypass leptin resistance in animal models
Objective To identify a safe and well-tolerated dose of rhvCNTF that causes weight
loss in obese adults.
Design, Setting, and Patients Twelve-week, double-blind, randomized, parallel-group, dose-ranging,
multicenter clinical trial conducted at 2 university obesity clinics and at
5 independent clinical research clinics from March 2000 to August 2001, and
including 173 nondiabetic obese adults, 82.6% of whom were women, with a mean
(SD) body mass index of 41.1 (4.1).
Interventions Patients were randomly assigned to receive daily for 12 weeks subcutaneous
injections of placebo (n = 32) or 0.3 µg/kg (n = 32), 1.0 µg/kg
(n = 38), or 2.0 µg/kg (n = 33) of rhvCNTF. Another group received 1.0
µg/kg for 8 weeks and placebo for 4 weeks (n = 38), but they were not
included in the primary analysis. All participants received instructions for
a reduced-calorie diet (World Health Organization formula minus 500 kcal/d).
Main Outcome Measures Change in weight during the 12-week double-blind treatment period and
proportion of patients who achieved a weight loss of at least 5%.
Results Of the 173 randomized patients, 123 (71%) completed the double-blind
dosing period. Mean (SEM) changes in kilograms from baseline body weights
were 0.1 (0.6) for placebo and −1.5 (0.6) for the 0.3, −4.1 (0.6)
for the 1.0, and –3.4 (0.7) for the 2.0 µg/kg of rhvCNTF dosage
groups (P<.001, test for trend). Two patients
(8.7%) in the placebo and 2 (8.3%) in the 0.3-µg/kg, 8 (29.6%) in the
1.0-µg/kg, and 5 (26%) in the 2.0-µg/kg treatment groups achieved
a weight loss of at least 5%. Recombinant human variant CNTF was generally
well tolerated although adverse events occurred in 75% of patients receiving
placebo and 78% to 93% of patients receiving rhvCNTF, in a dose-related fashion,
with mild injection site reactions as the most frequently reported adverse
Conclusions In this initial, dose-ranging, 12-week study, treatment with rhvCNTF
resulted in more weight loss than placebo. These preliminary findings require
confirmation in large prospective clinical trials.
Ciliary neurotrophic factor (CNTF), a protein with a molecular weight
of 22 kD, is an endogenous neuroprotective factor that is present in Schwann
cells and astrocytes but not in the peripheral circulation and is up-regulated
during injury to these cells.1,2 In
a study of patients with amyotrophic lateral sclerosis (ALS) evaluating possible
neuroprotective properties, CNTF did not alter disease progression. However,
CNTF was found to induce marked weight loss in these patients, who in general
were not obese at the outset of the trial.3 This
result was not fully understood until it was discovered that CNTF and the
weight-regulating hormone leptin have a related intracellular signaling mechanism.4
Recombinant human variant (rhv) CNTF is a genetically engineered variant
of CNTF with increased potency and improved pharmacological properties.5 It binds to the CNTF receptor and activates leptinlike
intracellular signaling pathways (Janus kinases and signal transducers and
activators of transcription 3) in hypothalamic nuclei, which regulate food
intake and body weight.4,6,7
Both leptin and rhvCNTF are capable of causing pronounced weight loss
in leptin-deficient obese mice.7-10 In
the diet-induced obese mouse model, leptin levels are already elevated and
additional exogenous leptin does not cause weight loss.7 Similarly,
obese humans have elevated serum leptin levels, and the efficacy of even high
doses of exogenous leptin for weight loss has been disappointing.11 This and other published research strongly suggest
that obese humans are leptin-resistant.12 By
contrast, rhvCNTF causes weight loss in diet-induced obese mice, suggesting
that this agent may bypass the known leptin-resistance present in this animal
model.7,13 This initial dose-ranging
study tested the hypothesis that rhvCNTF leads to weight loss in obese humans.
This randomized, placebo-controlled, double-blind, dose-ranging trial
of rhvCNTF was conducted at 7 sites in the United States. Each site received
institutional review board approval to conduct the study. All patients gave
written informed consent before any study procedures were performed. Eligible
patients included men and women aged 18 to 70 years with a body mass index
(BMI) of 35 to 50, inclusive. (BMI is calculated as weight in kilograms divided
by the square of height in meters.) Patients had to have a stable baseline
weight range of at least 4 kg and a stable physical activity level in the
12 weeks before study entry. Patients were excluded if they had diabetes mellitus,
a history of stroke, myocardial infarction, coronary artery disease, uncontrolled
hypertension, or uncontrolled hyperlipidemia. Pregnant or lactating women
were also excluded.
Recombinant human variant CNTF (Axokine) and matching placebo were manufactured
by Regeneron Pharmaceuticals, Inc, Tarrytown, NY, and provided for this study.
After a 2-week single blind run-in period of daily placebo injections,
patients were randomly assigned to receive placebo or 0.3, 1.0, or 2.0 µg/kg
per day of rhvCNTF subcutaneously for 12 weeks. An additional fifth group
received rhvCNTF at a dose of 1.0 µg/kg per day for 8 weeks before blindly
being switched to receive placebo for the remaining 4 weeks. Data from this
dosage group were analyzed in a separate comparison with the 1.0-µg/kg-continuous
dosage group. The intent of this withdrawal group was to observe the weight
of these patients in the last third of the double-blind dosing period in a
controlled and blinded way.
All subcutaneous study drug injections were self-administered daily
for the entire study period. Instructions for mild to moderate caloric restriction
were given to all patients during the 12-week active treatment phase; these
provided a 500-kcal/d deficit relative to the daily caloric requirements calculated
according to the World Health Organization formula.14 Nutritional
counseling, including 24-hour food recalls, was provided on 4 occasions. No
food diaries were collected.
After the 12-week double-blind dosing period, all patients were asked
to return for extended follow-up observations every 3 months for 1 year. Patients
and investigators continued to be blinded with respect to the study-drug treatment
assignment. At each of these visits body weights and adverse events were recorded.
At 6 and 12 months after the last study drug injection, patients received
Routine hematology and chemistry analyses were performed by a central
laboratory (Covance, Indianapolis, Ind). Anti-rhvCNTF antibodies were determined
by Regeneron Pharmaceuticals using an enzyme-linked immunosorbent assay. Briefly,
microtiter plates were coated with rhvCNTF, which bound antibodies that were
present in human serum. These rhvCNTF-bound and immobilized antibodies were
detected by the binding of a horseradish peroxidase–conjugated protein
A and subsequent addition of an horseradish peroxidase substrate. A mouse
monoclonal antibody selective for rhvCNTF and purified by protein A–affinity
column was used as a calibrator for the assay.
The primary efficacy end points were weight loss from baseline to the
end of the double-blind treatment period at 12 weeks, and the proportion of
patients losing a prespecified percentage (≥5%) of their body weight. Analyses
using the following data sets were carried out: Intent to treat, last observation
carried forward, all available data, and completers. The group that received
rhvCNTF for 8 weeks before receiving placebo was not included in these analyses.
The intent-to-treat data set included all randomized patients regardless of
whether they had a postrandomization weight measured including 6 patients
who had elevated prolactin levels at randomization and were excluded (Figure 1); patients without postrandomization
weight values were assumed to have had no change in weight. Patients in the
last-observation-carried-forward data set had to have at least 1 postrandomization
weight measurement, which was carried forward.
Statistical differences between means comparing all dose groups including
placebo were first analyzed by analysis of variance with a linear trend test
and clinical center as covariate. The prospectively defined analysis plan
stated that if the trend test reached statistical significance at the P<.05 level, then each dose group was to be compared
with placebo using 1 degree of freedom contrasts in the analysis-of-variance
model. Weight-loss-responder analyses, patients with ≥5% weight loss from
baseline body weight, were performed using the Cochran-Mantel-Haenszel procedure
for all dose groups, stratified by study center. Comparisons of individual
dose groups against placebo were also done by the Cochran-Mantel-Haenszel
procedure. All statistical tests were 2-sided. Safety data were tabulated
and evaluated descriptively. Analyses were performed using SAS statistical
software version 8.2 (SAS Inc, Cary, NC).
One hundred ninety-six patients entered a 2-week single-blind run-in
period and received daily placebo injections. One hundred seventy-nine patients
were subsequently randomly assigned to receive 0.3, 1.0, or 2.0 µg/kg
of rhvCNTF or placebo for 12 weeks. Six patients were excluded a few days
after double-blind treatment was started because of elevated serum prolactin
measurements at baseline (a protocol exclusion criterion), which resulted
in 173 evaluable patients (Figure 1).
The treatment groups were well matched at baseline with respect to weight
and race (Table 1). The majority
of the participants were women. Reasons for patients' dropping out up until
the end of the double-blind dosing period are displayed in Figure 1.
Results from the intent-to-treat analysis, the last-observation-carried-forward
analysis, and the completers analysis are shown in Table 2. The results for weight loss compared with placebo are consistent
among the different data sets and are statistically significant for those
who were in the 1.0- and 2.0-µg/kg dosage groups. Decreases in BMI were
statistically significant in all analyses at the 1.0- and 2.0-µg/kg
dosages compared with placebo. On average, patients lost weight in all active
treatment groups while patients receiving placebo showed nonsignificant weight
gain (Figure 2). Mean weight loss
in the 1.0-µg/kg-dosage group was continuous over the 12-week dosing
Patients who were switched in a blinded fashion from rhvCNTF at a dosage
of 1.0-µg/kg on day 56 to placebo appeared to stop losing weight, and
these patients on average maintained their weight compared with patients who
continued to receive rhvCNTF at 1.0 µg/kg (data not shown). Subgroup
analyses for the effects of weight loss stratified by patient age (divided
by tertiles), BMI (<42 or = 42), and race (white or not white) were not
significant. A positive test for trend was found for all analyses of responders
who lost at least 5% (Table 2).
Eighty-eight percent of all patients lost weight while treated with rhvCNTF.
Due to attrition, the number of patients in each dosage group decreased
over time. One-year follow-up data were available for 42% of the patients
who received placebo and 44% of those treated with rhvCNTF. For this reason,
the post hoc analysis of weight in the extended posttreatment follow-up was
conducted comparing all patients treated with rhvCNTF as a combined group
vs placebo (Figure 3). Compared
with the weight at the end of double-blind treatment at month 3, patients
who received placebo gained an average of 1.6 kg while patients treated with
rhvCNTF gained 0.1 kg at 6 months after the cessation of double-blind injections.
Compared with baseline, at month 9, patients in the placebo group had gained
1.7 kg while those in the combined rhvCNTF group had lost 2.9 kg. At month
12, after cessation of the study drug, those in the placebo group gained 0.5
kg, whereas those in the treatment group had gained 0.8 kg. The difference
in weight change from baseline between placebo and rhvCNTF treated patients
was statistically significantly different at month 3 (P<.001), month 6 (P = .006), month 9 (P = .006), and month 12 (P = .04),
but there was no difference at month 15 (P>.10; t test).
There was no difference between any of the dosage groups and placebo
in triglyceride, cholesterol, or insulin levels. However, decreases in fasting
serum insulin (P = .08 vs placebo) and triglyceride
levels were noted in patients who lost 5% or more of their body weight.
Patients and investigators were asked about treatment group assignment
at 8 and 12 weeks. At week 12, of all the patients receiving the study drug,
34% thought they were taking rhvCNTF, 40% thought they were taking placebo,
and 26% did not know. The investigators thought 34% of patients were taking
rhvCNTF, 48% thought patients were receiving placebo, and 18% said they did
At least 1 adverse event was reported by 75% of patients in the placebo
group and by 78.1% to 93.9% of patients in the rhvCNTF groups, with increasing
rates related to higher doses (Table 3).
The most frequently reported adverse events were injection site reactions,
nausea, infection, cough, and musculoskeletal pain. Of these, injections site
reactions, nausea, and cough were considered to be drug-related by the investigators.
Injection-site reactions consisted of nonindurated, mild-to-moderate redness
of the skin, which rarely were pruritic. Injection site reactions, if they
occurred, generally appeared within a day after dosing and resolved within
3 to 5 days.
Nausea was reported more frequently in patients treated with higher
doses of rhvCNTF and nausea-related dropouts were more frequent in the 2.0-µg/kg
dosage group (Table 3). Mean weight
loss in the rhvCNTF dosage groups did not differ between patients who reported
nausea vs those who did not. Increased cough was reported by 42.2% of patients
in the 2.0-µg/kg dosage group while the rates of cough in the lower-dosage
groups did not differ from placebo.
A total of 20 patients withdrew from the trial prematurely due to adverse
events (Figure 1): 4 (12.5%) of
32 patients in the placebo group and 16 (11.3%) of 141 patients receiving
rhvCNTF. No pattern of adverse events was seen in the placebo or lower dosage
groups. However, in the 2.0-µg/kg dosage group, 4 patients dropped out
due to nausea or nausea and vomiting vs 1 in the 1.0-µg/kg dosage group.
In our study, occurrence of herpes mouth sores was similar in placebo and
drug-treated patients. One serious adverse event occurred during the treatment
phase (a motor vehicle crash that was not considered drug related). No death
was reported in this study.
Overall, there were no changes in vital signs, or routine laboratory
parameters in patients in the active-treatment or placebo control groups.
In a dose-dependent fashion, values of C-reactive protein were slightly elevated
early into the dosing period but returned to baseline by the end of the active
dosing period. At the end of the double-blind dosing period, between 45% and
87% of patients in the rhvCNTF dosage groups had developed anti-rhvCNTF antibodies.
There was no apparent relationship between the dosage of rhvCNTF and the proportion
of patients developing antibodies. A total of 9 patients from among all rhvCNTF
treatment groups developed in vitro neutralizing anti-rhvCNTF antibodies.
Eight of these patients showed weight loss in the range of 0.6 kg to 5.5 kg
while 1 patient gained 1.0 kg during the active dosing period. The pattern
of adverse events in these 9 patients did not appear to differ from that in
other patients treated with rhvCNTF.
Ciliary neurotrophic factor signals through hypothalamic intracellular
pathways that are leptinlike. Both rhvCNTF and CNTF were shown to bypass leptin
resistance in animal models of obesity.4,6,7,13 In
this initial double-blind, randomized, placebo-controlled study, 12 weeks
of daily subcutaneous injection therapy with rhvCNTF resulted in more weight
loss than injection with placebo. On average, patients in the 1.0-µg/kg
dosage group experienced continuous weight loss during the double-blind dosing
period. It is possible that this weight loss results from rhvCNTF circumventing
leptin resistance in obese humans.13
Treatment of obesity is limited by rebound weight gain after cessation
of weight loss programs.15-17 Early
studies with fenfluramine,18 as well as recent
trials using sibutramine,19,20 show
that weight regain begins almost immediately after drug treatment is stopped.
It appears that more rapid weight loss is followed by more rapid weight regain.21 Hence, a weight loss regimen that does not result
in rapid weight regain would be highly desirable.
Patients treated with rhvCNTF did not appear to experience immediate
weight rebound when drug treatment was stopped. Toward the end of the 1-year
follow-up period patients treated with placebo started to lose some weight
while patients treated with rhvCNTF started to gain some weight, indicating
that the 2 groups might converge at some later time. However, these post hoc
findings should be considered preliminary in nature because of high attrition
(42% in the patients receiving placebo and 44% in patients receiving rhvCNTF)
and nonstudy related factors in these freely living individuals that start
to play a role. Prospective studies are currently under way to confirm these
Results from animal studies carried out in diet-induced obese mice7 showed that mice treated with rhvCNTF did not exhibit
compensatory overeating when drug injections were stopped. These animals did
not experience a rapid regain of the body weight lost during rhvCNTF administration.
In contrast, placebo-treated pair-fed control animals consumed a large amount
of food after removal of food restriction and did regain weight rapidly.7 This difference may be explained by the observation
that rhvCNTF suppresses hypothalamic hunger signals in rodents, including
expression of neuropeptide Y.4 Such hunger
signals are produced in elevated amounts in rodents that are subjected to
restricted food intake. It is possible that suppression of hunger signals
may be a mechanism operative in the obese patients treated with rhvCNTF. The
absence of increased hypothalamic hunger signals while patients are treated
with rhvCNTF might lead to a lack of compensatory overeating after treatment
cessation, which results in prolonged maintenance of weight loss.
At the end of active dosing, weight change was not different between
the 1.0- and 2.0-µg/kg dosage groups; however, the 2.0-µg/kg dosage
was associated with more adverse events. Nausea had been observed in patients
with ALS who were treated with CNTF in earlier studies3 and
also in volunteers treated with high single-doses of rhvCNTF in a first-in-human
study.22 It is likely that rhvCNTF in addition
to binding to the hypothalamic CNTF receptors also interacts with binding
sites in the area postrema, a neighboring region in the brain responsible
for nausea and vomiting. At the doses used in this study, reactivation of
herpetiform mouth sores was not different between placebo and drug-treated
patients. Earlier studies with CNTF in patients with ALS3 and
a phase 1 study with rhvCNTF in obese volunteers22 showed
reactivation of herpetiform mouth sores. The doses used in the latter study
were considerably higher (up to 16 µg/kg) than in our study.
Despite the high rates of adverse events, it appears that a dosage of
1.0 µg/kg or less of rhvCNTF is generally well tolerated. Weight loss
in patients with and without nausea was comparable, indicating that nausea
was not the factor effecting weight loss. Patients in the 2.0-µg/kg-dosage
group had higher incidence of nausea, vomiting, and cough, but weight loss
was not greater than in the 1.0-µg/kg dosage group. Taken together,
these observations support investigation of rhvCNTF at a dose of 1.0 µg/kg
for future studies. There were no deleterious changes of cardiovascular parameters
including blood pressure, heart rate, and heart valve function and anatomy
(echocardiographic data not shown).
Along with other therapeutic proteins administered subcutaneously, such
as insulin, rhvCNTF shares the potential to generate antibodies in humans.
Anti-rhvCNTF antibodies developed in many patients treated with rhvCNTF, but
the presence of binding antibodies, neutralizing anti-rhvCNTF antibodies,
or both did not appear to affect total weight loss or adverse event profile.
In summary, this short-term, dose-ranging study resulted in more weight
loss in those taking rhvCNTF than in those taking placebo. These preliminary
findings need to be confirmed in large-scale prospective studies.