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Clinical trial of gossypol as a male contraceptive drug. Part I. Efficacy study*
FERTILITY AND STERILITY Copyright Q 1987 The American Fertility Society
Vol. 48, No.3, September 1987 Printed in U.S.A.
Clinical trial of gossypol as a male contraceptive drug. Part I. Efficacy study*
Guo-zhen Liu, M.D.t Katherine Ch'iu Lyle, Ph.D.:j:§ Jian Cao, M.D. t Rockefeller Foundation, New York, New York, and Peking Union Medical College Hospital, Beijing, China
The main objective of the research is to study the effectiveness and safety of gossypol as a male contraceptive drug. Using a double-blind, randomized, controlled study design, gossypol was found to be an effective male antifertility drug, with no adverse effects on libido nor appetite. In terms of serum potassium levels, there were no statistical differences between gossypol and placebo groups at the end of the loading phase. However, through the ensuing 12 months of maintenance phase, a statistically significant trend toward reduced serum potassium level was evident. Fertil SteriI48:459, 1987
In the 1950s, gossypol, a pigment from the cotton plant, was found to be an accidental cause of male infertility in many rural communes in China, where ingestion of raw cotton seed oil was common. Since then, efforts have been made by Chinese scientists to develop this compound as a possible pill for men, which could be a valuable supplement to the existing methods of contraception. A double-blind, randomized, controlled clinical trial was carried out at the Peking Union Medical College Hospital in December 1981 and concluded in September 1983. The aim of this study was 3-fold: (1) to determine the contraceptive efficacy of gossypol in terms of the percentage of participants achieving a sperm count 4 X 106 or less, at the end of loading, as well as pregnancy rates during the maintenance phase; (2) to ascertain possible side effects, such as the incidence rates of fatigue, decrease in libido, and
Received March 6, 1987; revised and accepted May 12, 1987.
* Supported by Rockefeller Foundation grant 80029 to the Chinese Academy of Medical Sciences. t Peking Union Medical College Hospital. t Rockefeller Foundation. § Reprint requests: Katherine Ch'iu Lyle, Ph.D., Population Sciences Division, The Rockefeller Foundation, 1133 Avenue of the Americas, New York, New York 10036. Vol. 48, No.3, September 1987
loss of appetite; and (3) to determine the continuation rate of gossypol contraception. MATERIALS AND METHODS
Only male volunteers who met the entry criteria were enrolled. Entry criteria for each participant were as follows: (1) must be under age 40, (2) must have had at least one child, (3) must not have used gossypol before, (4) must have a sperm count higher than 40 million/cc and sperm motility higher than 60%, and (5) must be willing to use condoms for contraception during the loading phase, but no contraception during the maintenance phase, therefore, the wife was regularly exposed to the risk of pregnancy. For the initial 2! months of gossypol treatment, double-blind techniques and placebos were employed to examine such subjective questions as fatigue, loss of libido, and loss of appetite. In order to assume double-blinding for the first 75-day loading phase, volunteers were randomized into two groups to receive gossypol pills (20 mg/day) and placebos, accordingly. Gossypol pills were made of gossypol acetic acid and were purified by the Institute of Materia Medica of the Chinese Academy of Medical Sciences. The purity of gossypol is above 99%. The placebos were made of inert materials (mainly Liu et al. Gossypol contraception
459
Table 1 Percentage of Participants Who Experienced Side Effects: Gossypol Versus Placebo
Number of volunteers
Gossypol
Placebo
Side effects
(69)a
(74)a
Z score
Fatigue Appetite disturbance Libido decrease
13% (9) 7% (5) 9% (6)
5% (4) 7% (5) 3% (3)
1.3 (P> 0.05) -0.2 (P> 0.05) 1.2 (P> 0.05)
a
Number in parentheses indicates sample size.
starch and sugar). Both the gossypol and placebo pills were bottled the same and were sugar-coated and made to look and taste alike. One hundred fifty-two volunteers were enrolled: 75 on a gossypol regimen of 20 mg/day as the treatment group and 77 on placebos as the control group. After the decoding of the double-blind study and division of volunteers into the treatment and placebo groups at the end of the loading phase, the treatment group started the maintenance phase with a regimen of 50 mg/week, and the placebo group started on the real gossypol treatment of 20 mg/day to initiate the loading phase. Therefore, the volunteers in the placebo group or their wives needed an additional 75 days of contraceptive protection during this loading phase. After the 75-day loading phase, these volunteers started the maintenance phase by a regimen of 50 mg/week. Each of the 152 volunteers who participated in the study continued use of gossypol for at least 14! months (i.e., 2! months for loading phase and 12 months for maintenance phase), unless he elected to terminate use of gossypol prior to that time.
RESULTS Loading Phase
By the end ofthe double-blind loading phase, 11 participants from the gossypol treatment group and 3 from the placebo group had withdrawn. In terms of efficacy, of the 64 gossypol-treated participants, 31% achieved azoospermia and 61 % had a sperm count < 4 X 106 and 3% (2 participants) had a sperm count between 5 and 9 million/cc; the remaining 5% (3 participants) had sperm counts >10 million/cc. A 92% efficacy rate was achieved at the end of the loading phase. Sperm counts for the placebo group remained unchanged. Incidence rates for fatigue, decrease of libido, and appetite between the two groups showed no statistically significant differences (Table 1) nor were any differences observed for body weight, hemoglobin, serum potassium, or blood pressure. 460
Liu et al.
Gossypol contraception
Table 2 Sperm Count (million/cc) in Volunteers at Various Gossypol Treatment Intervals
Sperm count
End of loading
3 Months
6 Months
9 Months
12 Months
0 1-4 5-9 >10
60 48 6 10
111 4 1 2
99 4 0 5
81 7 3 4
77 7 0 2
Total
124
118
108
95
86
Maintenance Phase
Efficacy rates (in terms of sperm count <4 X 106 ) of 87%, 97%, 95%, 92%, and 98% were achieved at the end of loading, 3, 6, 9, and 12 months of maintenance phase, respectively (Table 2). There were no statistically significant differences among the mean for body weight, hemoglobin, and blood pressure among the various intervals of treatment (Table 3). However, serum potassium showed a significant decline between various intervals (Table 3). For subjective data, there were no statistically significant differences for the decrease of appetite and libido among the various intervals of treatment (Table 4). For fatigue, differences were observed among the various treatment intervals with chisquare value of 18.08 with 4 df (P < 0.05). A priori null hypothesis was that the occurrence of fatigue during the loading did not differ from the occurrence during the maintenance phase. Using partitioning technique, a chi-squarediff value of 16.49 was obtained, indicating that fatigue occurred more frequently during the loading than during the maintenance phase. Additional testing showed no differences among fatigue occurrence during the various intervals of maintenance phase. For I-year continuation study using the modified life-table analysis, attrition rates were 26% and 39% at 6 and 12 months of gossypol use, respectively. None of the wives of the volunteers became pregnant. The net cumulative termination rates for the 6 and 12 months were 8.6 and 14.5% for medical reasons (i.e., fatigue, appetite decrease, libido decrease, or other medicals); 10.5 and 15.8% for userelated reasons (i.e., storage, schedule of use, changing to other contraceptives, or just did not like the gossypol pills); 5.3 and 6.6% for personal reasons (i.e., planning pregnancy, family objection to contraception, widowed or divorced); and 1.3 and 3.0% for technical reasons (i.e., moving or end of study). The continuation rates were 74.3% and Fertility and Sterility
Table 3
Body Weight, Hemoglobin, Blood Pressure in Volunteers at Various Gossypol Treatment Intervals (Mean ± SE) Maintenance phase Item
Admission
End of loading
Body weight (kg) Hemoglobin (gmllOO ml) Blood pressure Systolic (mm Hg) Diastolic (mm Hg) Serum potassium (mEq/1)
63.6 ± 0.7 15.6 ± 0.1
63.2 ± 0.8 15.7 ± 0.1
63.0 ± 0.8 15.8 ± 0.1
63.1 ± 0.8 15.8 ± 0.1
63.4 ± 0.9 15.7 ± 0.1
63.6 ± 1.0 16.0 ± 0.1
0.11 (P> 0.05) 1.5 (P> 0.05)
115.2 ± 0.9 81.3 ± 0.7 4.3 ± 0.03
115.0 ± 1.0 81.7 ± 0.8 4.1 ± 0.04
116.0 ± 1.0 82.8 ± 0.8 3.9 ± 0.04
115.0 ± 1.0 82.2 ± 0.8 3.8 ± 0.04
113.4 ± 1.1 79.6 ± 0.9 3.9 ± 0.04
112.0 ± 1.2 79.3 ± 0.9 3.8 ± 0.04
1.1 (P> 0.05) 2.8 (P> 0.05) 30.03 (P < 0.05)
Table 4
3 months
6 months
9 months
12 months
F score
Percentage of Volunteers with Appetite, Libido Decrease, and Fatigue at Various Gossypol Treatment Intervals Maintenance phase
Item
End of loading
3 months
6 months
9 months
12 months
2
Appetite decrease Libido decrease Fatigue
2.4 4.0 1.0
1.0 1.0 2.0
0.0 1.0 1.0
1.0 1.0 3.0
0.0 0.0 0.0
4.7 (P> 0.05) 7.2 (P> 0.05) 18.08 (P < 0.05)
61.2% at 6 and 12 months of gossypol use, respectively (Table 5). DISCUSSION
The most serious side effect of gossypol contraception was the presumed lowering of serum potassium levels. However, the mechanism of gossypolinduced hypokalemia is not yet well understood. Some speculate 1 that fatigue may be a prodromal symptom of subsequent hypokalemic paralytic attack. In this study, 17 cases complained of fatigue. The before-and-after comparison of serum potassium values indicated that there was a significant decrease in serum potassium levels at the time Table 5 Net Cumulative Termination and Continuation Rates After 6 and 12 Months of Gossypol Use" Reason
6 Months
12 Months
Pregnancy Medical reasons Fatigue Appetite decrease Libido decrease Other medicals Methods related Personal reasons Technical Total termination Continuation Man/months Lost to follow-up Total enrolled
0.0 ± 0.0
0.0 ± 0.0
± 0.13 ± 0.07 ± 0.004 ± 0.04 ± 0.29 ± 0.11 ± 0.01 25.7 74.3 ± 3.52 771.5 0 152
3.3 ± 0.06 4.6 ± 0.09 1.3 ± 0.014 5.3 ± 0.11 15.8 ± 0.57 6.6 ± 0.15 2.0 ± 0.02 38.3 61.2 ± 4.07 1392.5 0
1.3 4.0 0.7 2.6 10.5 5.3 1.3
" The cutoff date was June 30, 1983. Vol. 48, No.3, September 1987
when volunteers complained of fatigue. Two cases merit special mentioning. Patient 50 had an admission serum potassium value of 4.8 mEq/l; it then declined to 3.7 mEq/1 at the end of loading. During the following 2 months of maintenance phase, patient 50 developed stiffness of the neck and his serum potassium value was 2.6 mEqll and gossypol treatment was discontinued. The serum potassium values of patient 103 were 3.5 at admission, 3.7 at the end of loading, and 3.8, 3.6, and 2.4 mEq/1 at 3, 6, and 9 months of maintenance phase. During the ninth month of maintenance phase, patient 103 developed numbness of both hands and gossypol treatment was discontinued. In light of the findings reduction in serum potassium levels as a function of time as well as the generally lower serum potassium levels found among the Chinese population,2 the thrust of gossypol research in China, at present, is to supplement gossypol contraception with potassium salt or with a potassium blocker to ameliorate gossypol-related hypokalemia. Acknowledgments. We thank Mr. Baoyin Li and Mr. Changen Wang for technical assistance.
REFERENCES 1. Qian SZ, Wang ZG: Gossypol: a potential antifertility agent for males. Ann Rev Pharmacol Toxicol 24:329, 1984 2. Qian SZ: Effect of gossypol on potassium and prostaglandin metabolism and mechanism of action of gossypol. In Recent Advances in Fertility Regulation, Edited by CF Chang, D Griffin, A Woolman. Geneva, Atar, 1981, p 152
Liu et al.
Gossypol contraception
461
Vol. 48, No.3, September 1987 Printed in U.S.A.
Clinical trial of gossypol as a male contraceptive drug. Part I. Efficacy study*
Guo-zhen Liu, M.D.t Katherine Ch'iu Lyle, Ph.D.:j:§ Jian Cao, M.D. t Rockefeller Foundation, New York, New York, and Peking Union Medical College Hospital, Beijing, China
The main objective of the research is to study the effectiveness and safety of gossypol as a male contraceptive drug. Using a double-blind, randomized, controlled study design, gossypol was found to be an effective male antifertility drug, with no adverse effects on libido nor appetite. In terms of serum potassium levels, there were no statistical differences between gossypol and placebo groups at the end of the loading phase. However, through the ensuing 12 months of maintenance phase, a statistically significant trend toward reduced serum potassium level was evident. Fertil SteriI48:459, 1987
In the 1950s, gossypol, a pigment from the cotton plant, was found to be an accidental cause of male infertility in many rural communes in China, where ingestion of raw cotton seed oil was common. Since then, efforts have been made by Chinese scientists to develop this compound as a possible pill for men, which could be a valuable supplement to the existing methods of contraception. A double-blind, randomized, controlled clinical trial was carried out at the Peking Union Medical College Hospital in December 1981 and concluded in September 1983. The aim of this study was 3-fold: (1) to determine the contraceptive efficacy of gossypol in terms of the percentage of participants achieving a sperm count 4 X 106 or less, at the end of loading, as well as pregnancy rates during the maintenance phase; (2) to ascertain possible side effects, such as the incidence rates of fatigue, decrease in libido, and
Received March 6, 1987; revised and accepted May 12, 1987.
* Supported by Rockefeller Foundation grant 80029 to the Chinese Academy of Medical Sciences. t Peking Union Medical College Hospital. t Rockefeller Foundation. § Reprint requests: Katherine Ch'iu Lyle, Ph.D., Population Sciences Division, The Rockefeller Foundation, 1133 Avenue of the Americas, New York, New York 10036. Vol. 48, No.3, September 1987
loss of appetite; and (3) to determine the continuation rate of gossypol contraception. MATERIALS AND METHODS
Only male volunteers who met the entry criteria were enrolled. Entry criteria for each participant were as follows: (1) must be under age 40, (2) must have had at least one child, (3) must not have used gossypol before, (4) must have a sperm count higher than 40 million/cc and sperm motility higher than 60%, and (5) must be willing to use condoms for contraception during the loading phase, but no contraception during the maintenance phase, therefore, the wife was regularly exposed to the risk of pregnancy. For the initial 2! months of gossypol treatment, double-blind techniques and placebos were employed to examine such subjective questions as fatigue, loss of libido, and loss of appetite. In order to assume double-blinding for the first 75-day loading phase, volunteers were randomized into two groups to receive gossypol pills (20 mg/day) and placebos, accordingly. Gossypol pills were made of gossypol acetic acid and were purified by the Institute of Materia Medica of the Chinese Academy of Medical Sciences. The purity of gossypol is above 99%. The placebos were made of inert materials (mainly Liu et al. Gossypol contraception
459
Table 1 Percentage of Participants Who Experienced Side Effects: Gossypol Versus Placebo
Number of volunteers
Gossypol
Placebo
Side effects
(69)a
(74)a
Z score
Fatigue Appetite disturbance Libido decrease
13% (9) 7% (5) 9% (6)
5% (4) 7% (5) 3% (3)
1.3 (P> 0.05) -0.2 (P> 0.05) 1.2 (P> 0.05)
a
Number in parentheses indicates sample size.
starch and sugar). Both the gossypol and placebo pills were bottled the same and were sugar-coated and made to look and taste alike. One hundred fifty-two volunteers were enrolled: 75 on a gossypol regimen of 20 mg/day as the treatment group and 77 on placebos as the control group. After the decoding of the double-blind study and division of volunteers into the treatment and placebo groups at the end of the loading phase, the treatment group started the maintenance phase with a regimen of 50 mg/week, and the placebo group started on the real gossypol treatment of 20 mg/day to initiate the loading phase. Therefore, the volunteers in the placebo group or their wives needed an additional 75 days of contraceptive protection during this loading phase. After the 75-day loading phase, these volunteers started the maintenance phase by a regimen of 50 mg/week. Each of the 152 volunteers who participated in the study continued use of gossypol for at least 14! months (i.e., 2! months for loading phase and 12 months for maintenance phase), unless he elected to terminate use of gossypol prior to that time.
RESULTS Loading Phase
By the end ofthe double-blind loading phase, 11 participants from the gossypol treatment group and 3 from the placebo group had withdrawn. In terms of efficacy, of the 64 gossypol-treated participants, 31% achieved azoospermia and 61 % had a sperm count < 4 X 106 and 3% (2 participants) had a sperm count between 5 and 9 million/cc; the remaining 5% (3 participants) had sperm counts >10 million/cc. A 92% efficacy rate was achieved at the end of the loading phase. Sperm counts for the placebo group remained unchanged. Incidence rates for fatigue, decrease of libido, and appetite between the two groups showed no statistically significant differences (Table 1) nor were any differences observed for body weight, hemoglobin, serum potassium, or blood pressure. 460
Liu et al.
Gossypol contraception
Table 2 Sperm Count (million/cc) in Volunteers at Various Gossypol Treatment Intervals
Sperm count
End of loading
3 Months
6 Months
9 Months
12 Months
0 1-4 5-9 >10
60 48 6 10
111 4 1 2
99 4 0 5
81 7 3 4
77 7 0 2
Total
124
118
108
95
86
Maintenance Phase
Efficacy rates (in terms of sperm count <4 X 106 ) of 87%, 97%, 95%, 92%, and 98% were achieved at the end of loading, 3, 6, 9, and 12 months of maintenance phase, respectively (Table 2). There were no statistically significant differences among the mean for body weight, hemoglobin, and blood pressure among the various intervals of treatment (Table 3). However, serum potassium showed a significant decline between various intervals (Table 3). For subjective data, there were no statistically significant differences for the decrease of appetite and libido among the various intervals of treatment (Table 4). For fatigue, differences were observed among the various treatment intervals with chisquare value of 18.08 with 4 df (P < 0.05). A priori null hypothesis was that the occurrence of fatigue during the loading did not differ from the occurrence during the maintenance phase. Using partitioning technique, a chi-squarediff value of 16.49 was obtained, indicating that fatigue occurred more frequently during the loading than during the maintenance phase. Additional testing showed no differences among fatigue occurrence during the various intervals of maintenance phase. For I-year continuation study using the modified life-table analysis, attrition rates were 26% and 39% at 6 and 12 months of gossypol use, respectively. None of the wives of the volunteers became pregnant. The net cumulative termination rates for the 6 and 12 months were 8.6 and 14.5% for medical reasons (i.e., fatigue, appetite decrease, libido decrease, or other medicals); 10.5 and 15.8% for userelated reasons (i.e., storage, schedule of use, changing to other contraceptives, or just did not like the gossypol pills); 5.3 and 6.6% for personal reasons (i.e., planning pregnancy, family objection to contraception, widowed or divorced); and 1.3 and 3.0% for technical reasons (i.e., moving or end of study). The continuation rates were 74.3% and Fertility and Sterility
Table 3
Body Weight, Hemoglobin, Blood Pressure in Volunteers at Various Gossypol Treatment Intervals (Mean ± SE) Maintenance phase Item
Admission
End of loading
Body weight (kg) Hemoglobin (gmllOO ml) Blood pressure Systolic (mm Hg) Diastolic (mm Hg) Serum potassium (mEq/1)
63.6 ± 0.7 15.6 ± 0.1
63.2 ± 0.8 15.7 ± 0.1
63.0 ± 0.8 15.8 ± 0.1
63.1 ± 0.8 15.8 ± 0.1
63.4 ± 0.9 15.7 ± 0.1
63.6 ± 1.0 16.0 ± 0.1
0.11 (P> 0.05) 1.5 (P> 0.05)
115.2 ± 0.9 81.3 ± 0.7 4.3 ± 0.03
115.0 ± 1.0 81.7 ± 0.8 4.1 ± 0.04
116.0 ± 1.0 82.8 ± 0.8 3.9 ± 0.04
115.0 ± 1.0 82.2 ± 0.8 3.8 ± 0.04
113.4 ± 1.1 79.6 ± 0.9 3.9 ± 0.04
112.0 ± 1.2 79.3 ± 0.9 3.8 ± 0.04
1.1 (P> 0.05) 2.8 (P> 0.05) 30.03 (P < 0.05)
Table 4
3 months
6 months
9 months
12 months
F score
Percentage of Volunteers with Appetite, Libido Decrease, and Fatigue at Various Gossypol Treatment Intervals Maintenance phase
Item
End of loading
3 months
6 months
9 months
12 months
2
Appetite decrease Libido decrease Fatigue
2.4 4.0 1.0
1.0 1.0 2.0
0.0 1.0 1.0
1.0 1.0 3.0
0.0 0.0 0.0
4.7 (P> 0.05) 7.2 (P> 0.05) 18.08 (P < 0.05)
61.2% at 6 and 12 months of gossypol use, respectively (Table 5). DISCUSSION
The most serious side effect of gossypol contraception was the presumed lowering of serum potassium levels. However, the mechanism of gossypolinduced hypokalemia is not yet well understood. Some speculate 1 that fatigue may be a prodromal symptom of subsequent hypokalemic paralytic attack. In this study, 17 cases complained of fatigue. The before-and-after comparison of serum potassium values indicated that there was a significant decrease in serum potassium levels at the time Table 5 Net Cumulative Termination and Continuation Rates After 6 and 12 Months of Gossypol Use" Reason
6 Months
12 Months
Pregnancy Medical reasons Fatigue Appetite decrease Libido decrease Other medicals Methods related Personal reasons Technical Total termination Continuation Man/months Lost to follow-up Total enrolled
0.0 ± 0.0
0.0 ± 0.0
± 0.13 ± 0.07 ± 0.004 ± 0.04 ± 0.29 ± 0.11 ± 0.01 25.7 74.3 ± 3.52 771.5 0 152
3.3 ± 0.06 4.6 ± 0.09 1.3 ± 0.014 5.3 ± 0.11 15.8 ± 0.57 6.6 ± 0.15 2.0 ± 0.02 38.3 61.2 ± 4.07 1392.5 0
1.3 4.0 0.7 2.6 10.5 5.3 1.3
" The cutoff date was June 30, 1983. Vol. 48, No.3, September 1987
when volunteers complained of fatigue. Two cases merit special mentioning. Patient 50 had an admission serum potassium value of 4.8 mEq/l; it then declined to 3.7 mEq/1 at the end of loading. During the following 2 months of maintenance phase, patient 50 developed stiffness of the neck and his serum potassium value was 2.6 mEqll and gossypol treatment was discontinued. The serum potassium values of patient 103 were 3.5 at admission, 3.7 at the end of loading, and 3.8, 3.6, and 2.4 mEq/1 at 3, 6, and 9 months of maintenance phase. During the ninth month of maintenance phase, patient 103 developed numbness of both hands and gossypol treatment was discontinued. In light of the findings reduction in serum potassium levels as a function of time as well as the generally lower serum potassium levels found among the Chinese population,2 the thrust of gossypol research in China, at present, is to supplement gossypol contraception with potassium salt or with a potassium blocker to ameliorate gossypol-related hypokalemia. Acknowledgments. We thank Mr. Baoyin Li and Mr. Changen Wang for technical assistance.
REFERENCES 1. Qian SZ, Wang ZG: Gossypol: a potential antifertility agent for males. Ann Rev Pharmacol Toxicol 24:329, 1984 2. Qian SZ: Effect of gossypol on potassium and prostaglandin metabolism and mechanism of action of gossypol. In Recent Advances in Fertility Regulation, Edited by CF Chang, D Griffin, A Woolman. Geneva, Atar, 1981, p 152
Liu et al.
Gossypol contraception
461