Skip to content

Study · Randomized controlled trial · 2026

15 results

Effect of Age and Age-Defined Menopausal Status on Linaclotide Efficacy and Safety in Adults With Irritable Bowel Syndrome With Constipation or Chronic Idiopathic Constipation: Post Hoc Analyses of Phase 2b/3 Studies.

Chang L, Staller K, Houghton LA, Yerneni N, Higgins S, Chen W, Wu J, Ford AC, Feuerstadt P, Brenner DM

Neurogastroenterology and motility1 Sept 2026

Summary

BackgroundThis post hoc study explored the effect of age and age-defined menopausal status on linaclotide efficacy and safety in adults with irritable bowel syndrome with constipation (IBS-C) or chronic idiopathic constipation (CIC).MethodsData were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C). Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status. Efficacy endpoints included change from baseline and time to response in complete spontaneous bowel movement (CSBM) frequency and abdominal symptoms.ResultsLinaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups. Abdominal symptoms reduced from baseline versus placebo across all subgroups. Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age (IBS-C, < 65 years, placebo: 4.0; 290 μg: 2.0; ≥ 65 years, placebo: 3.0; 290 μg: 2.0; CIC, < 65 years, placebo: 4.0; 72 μg: 3.0; 145 μg: 2.0; ≥ 65 years, placebo: 5.0; 72 μg: 3.0; 145 μg: 1.5) and age-defined menopausal subgroups.ConclusionIn this exploratory post hoc analysis, linaclotide was associated with improvements in bowel and abdominal symptoms across age and age-defined menopausal subgroups, with a safety profile consistent with previous studies, suggesting that age and menopausal status did not meaningfully influence treatment outcomes.
CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study15

15 results from studies that gave the peptide. 15 results from people.

  1. 01HumanRandomized controlled trialEfficacy outcome

    In IBS-C patients under 65, weekly CSBM frequency increased by 2.3 with linaclotide versus 0.8 with placebo.

    In plain wordsIn IBS-C patients under 65, linaclotide increased complete spontaneous bowel movements more than placebo.

    Outcome
    IncreaseWeekly CSBM frequency, IBS-C under 65
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    290 μgAs given in this study (human).

    Measurements

    Weekly CSBM change
    2.3 CSBM/week
    linaclotide 290 μg; age <65
    Weekly CSBM change
    0.8 CSBM/week
    placebo; IBS-C age <65

    Source sentences

    Summary
    Linaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  2. 02HumanRandomized controlled trialEfficacy outcome

    In IBS-C patients aged at least 65, weekly CSBM frequency increased by 2.6 with linaclotide versus 0.9 with placebo.

    In plain wordsIn older IBS-C patients, linaclotide increased complete spontaneous bowel movements more than placebo.

    Outcome
    IncreaseWeekly CSBM frequency, IBS-C at least 65
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    290 μgAs given in this study (human).

    Measurements

    Weekly CSBM change
    2.6 CSBM/week
    linaclotide 290 μg; age ≥65
    Weekly CSBM change
    0.9 CSBM/week
    placebo; IBS-C age ≥65

    Source sentences

    Summary
    Linaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  3. 03HumanRandomized controlled trialEfficacy outcome

    In CIC patients under 65, weekly CSBM frequency increased by 1.7 with linaclotide 72 μg versus 0.7 with placebo.

    In plain wordsIn CIC patients under 65, lower-dose linaclotide increased complete spontaneous bowel movements more than placebo.

    Outcome
    IncreaseWeekly CSBM frequency, CIC under 65, lower dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    72 μgAs given in this study (human).

    Measurements

    Weekly CSBM change
    1.7 CSBM/week
    linaclotide 72 μg; age <65
    Weekly CSBM change
    0.7 CSBM/week
    placebo; CIC age <65

    Source sentences

    Summary
    Linaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  4. 04HumanRandomized controlled trialEfficacy outcome

    In CIC patients under 65, weekly CSBM frequency increased by 2.0 with linaclotide 145 μg versus 0.7 with placebo.

    In plain wordsIn CIC patients under 65, higher-dose linaclotide increased complete spontaneous bowel movements more than placebo.

    Outcome
    IncreaseWeekly CSBM frequency, CIC under 65, higher dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    145 μgAs given in this study (human).

    Measurements

    Weekly CSBM change
    2 CSBM/week
    linaclotide 145 μg; age <65
    Weekly CSBM change
    0.7 CSBM/week
    placebo; CIC age <65

    Source sentences

    Summary
    Linaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  5. 05HumanRandomized controlled trialEfficacy outcome

    In CIC patients aged at least 65, weekly CSBM frequency increased by 1.5 with linaclotide 72 μg versus 0.9 with placebo.

    In plain wordsIn older CIC patients, lower-dose linaclotide increased complete spontaneous bowel movements more than placebo.

    Outcome
    IncreaseWeekly CSBM frequency, CIC at least 65, lower dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    72 μgAs given in this study (human).

    Measurements

    Weekly CSBM change
    1.5 CSBM/week
    linaclotide 72 μg; age ≥65
    Weekly CSBM change
    0.9 CSBM/week
    placebo; CIC age ≥65

    Source sentences

    Summary
    Linaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  6. 06HumanRandomized controlled trialEfficacy outcome

    In CIC patients aged at least 65, weekly CSBM frequency increased by 2.3 with linaclotide 145 μg versus 0.9 with placebo.

    In plain wordsIn older CIC patients, higher-dose linaclotide increased complete spontaneous bowel movements more than placebo.

    Outcome
    IncreaseWeekly CSBM frequency, CIC at least 65, higher dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    145 μgAs given in this study (human).

    Measurements

    Weekly CSBM change
    2.3 CSBM/week
    linaclotide 145 μg; age ≥65
    Weekly CSBM change
    0.9 CSBM/week
    placebo; CIC age ≥65

    Source sentences

    Summary
    Linaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  7. 07HumanRandomized controlled trialEfficacy outcome

    In women with IBS-C or CIC, linaclotide increased weekly CSBM frequency versus placebo across age-defined menopausal subgroups.

    In plain wordsIn women with IBS-C or CIC, linaclotide increased complete spontaneous bowel movements more than placebo across age-defined menopausal subgroups.

    Outcome
    IncreaseWeekly CSBM frequency across menopausal subgroups
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    Dose not stated

    Source sentences

    Summary
    Linaclotide increased weekly CSBM frequency from baseline versus placebo across age (IBS-C, < 65 years, placebo: 0.8; 290 μg: 2.3; ≥ 65 years, placebo: 0.9; 290 μg: 2.6; CIC, < 65 years, placebo: 0.7; 72 μg: 1.7; 145 μg: 2.0; ≥ 65 years, placebo: 0.9; 72 μg: 1.5; 145 μg: 2.3) and menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  8. 08HumanRandomized controlled trialEfficacy outcome

    In adults with IBS-C or CIC, linaclotide reduced abdominal symptoms from baseline versus placebo across all age and menopausal subgroups.

    In plain wordsIn adults with IBS-C or CIC, linaclotide reduced abdominal symptoms more than placebo across age and menopausal subgroups.

    Outcome
    DecreaseAbdominal symptoms across subgroups
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    Dose not stated

    Source sentences

    Summary
    Abdominal symptoms reduced from baseline versus placebo across all subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  9. 09HumanRandomized controlled trialEfficacy outcome

    In IBS-C patients under 65, median time to the specified CSBM increase was 2.0 weeks with linaclotide versus 4.0 with placebo.

    In plain wordsIn IBS-C patients under 65, linaclotide reached the bowel movement response sooner than placebo.

    Outcome
    DecreaseCSBM response time, IBS-C under 65
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    290 μgAs given in this study (human).

    Measurements

    Median response time
    2 weeks
    linaclotide 290 μg; IBS-C age <65
    Median response time
    4 weeks
    placebo; IBS-C age <65

    Source sentences

    Summary
    Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age (IBS-C, < 65 years, placebo: 4.0; 290 μg: 2.0;
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  10. 10HumanRandomized controlled trialEfficacy outcome

    In IBS-C patients aged at least 65, median time to the specified CSBM increase was 2.0 weeks with linaclotide versus 3.0 with placebo.

    In plain wordsIn older IBS-C patients, linaclotide reached the bowel movement response sooner than placebo.

    Outcome
    DecreaseCSBM response time, IBS-C at least 65
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    290 μgAs given in this study (human).

    Measurements

    Median response time
    2 weeks
    linaclotide 290 μg; IBS-C age ≥65
    Median response time
    3 weeks
    placebo; IBS-C age ≥65

    Source sentences

    Summary
    Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age (IBS-C, < 65 years, placebo: 4.0; 290 μg: 2.0; ≥ 65 years, placebo: 3.0; 290 μg: 2.0; CIC,
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  11. 11HumanRandomized controlled trialEfficacy outcome

    In CIC patients under 65, median time to the specified CSBM increase was 3.0 weeks with linaclotide 72 μg versus 4.0 with placebo.

    In plain wordsIn CIC patients under 65, lower-dose linaclotide reached the bowel movement response sooner than placebo.

    Outcome
    DecreaseCSBM response time, CIC under 65, lower dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    72 μgAs given in this study (human).

    Measurements

    Median response time
    3 weeks
    linaclotide 72 μg; CIC age <65
    Median response time
    4 weeks
    placebo; CIC age <65

    Source sentences

    Summary
    Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age (IBS-C, < 65 years, placebo: 4.0; 290 μg: 2.0; ≥ 65 years, placebo: 3.0; 290 μg: 2.0; CIC, < 65 years, placebo: 4.0; 72 μg: 3.0; 145 μg: 2.0; ≥ 65 years, placebo: 5.0; 72 μg: 3.0; 145 μg: 1.5) and age-defined menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  12. 12HumanRandomized controlled trialEfficacy outcome

    In CIC patients under 65, median time to the specified CSBM increase was 2.0 weeks with linaclotide 145 μg versus 4.0 with placebo.

    In plain wordsIn CIC patients under 65, higher-dose linaclotide reached the bowel movement response sooner than placebo.

    Outcome
    DecreaseCSBM response time, CIC under 65, higher dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    145 μgAs given in this study (human).

    Measurements

    Median response time
    2 weeks
    linaclotide 145 μg; CIC age <65
    Median response time
    4 weeks
    placebo; CIC age <65

    Source sentences

    Summary
    Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age (IBS-C, < 65 years, placebo: 4.0; 290 μg: 2.0; ≥ 65 years, placebo: 3.0; 290 μg: 2.0; CIC, < 65 years, placebo: 4.0; 72 μg: 3.0; 145 μg: 2.0; ≥ 65 years, placebo: 5.0; 72 μg: 3.0; 145 μg: 1.5) and age-defined menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  13. 13HumanRandomized controlled trialEfficacy outcome

    In CIC patients aged at least 65, median time to the specified CSBM increase was 3.0 weeks with linaclotide 72 μg versus 5.0 with placebo.

    In plain wordsIn older CIC patients, lower-dose linaclotide reached the bowel movement response sooner than placebo.

    Outcome
    DecreaseCSBM response time, CIC at least 65, lower dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    72 μgAs given in this study (human).

    Measurements

    Median response time
    3 weeks
    linaclotide 72 μg; CIC age ≥65
    Median response time
    5 weeks
    placebo; CIC age ≥65

    Source sentences

    Summary
    Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age (IBS-C, < 65 years, placebo: 4.0; 290 μg: 2.0; ≥ 65 years, placebo: 3.0; 290 μg: 2.0; CIC, < 65 years, placebo: 4.0; 72 μg: 3.0; 145 μg: 2.0; ≥ 65 years, placebo: 5.0; 72 μg: 3.0; 145 μg: 1.5) and age-defined menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  14. 14HumanRandomized controlled trialEfficacy outcome

    In CIC patients aged at least 65, median time to the specified CSBM increase was 1.5 weeks with linaclotide 145 μg versus 5.0 with placebo.

    In plain wordsIn older CIC patients, higher-dose linaclotide reached the bowel movement response sooner than placebo.

    Outcome
    DecreaseCSBM response time, CIC at least 65, higher dose
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    145 μgAs given in this study (human).

    Measurements

    Median response time
    1.5 weeks
    linaclotide 145 μg; CIC age ≥65
    Median response time
    5 weeks
    placebo; CIC age ≥65

    Source sentences

    Summary
    Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age (IBS-C, < 65 years, placebo: 4.0; 290 μg: 2.0; ≥ 65 years, placebo: 3.0; 290 μg: 2.0; CIC, < 65 years, placebo: 4.0; 72 μg: 3.0; 145 μg: 2.0; ≥ 65 years, placebo: 5.0; 72 μg: 3.0; 145 μg: 1.5) and age-defined menopausal subgroups.
    2 context sentences
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.
  15. 15HumanRandomized controlled trialEfficacy outcome

    In women with IBS-C or CIC, linaclotide shortened time to the specified weekly CSBM increase versus placebo across age-defined menopausal subgroups.

    In plain wordsIn women with IBS-C or CIC, linaclotide reached the bowel movement response sooner than placebo across age-defined menopausal subgroups.

    Outcome
    DecreaseCSBM response time across menopausal subgroups
    Study

    n: not reported in source

    Comparator
    Placebo
    Analysis
    Exploratory
    Outcome group
    Bowel Function · Gastrointestinal
    Studied dose
    Dose not stated

    Source sentences

    Summary
    Median time (weeks) to an increase from baseline in weekly CSBM rate of ≥ 1 was shorter with linaclotide versus placebo across age
    3 context sentences
    Summary · context
    and age-defined menopausal subgroups.
    Summary · context
    Data were pooled from eight randomized, placebo-controlled studies of linaclotide 72 μg (CIC), 145 μg (CIC), or 290 μg (IBS-C).
    Summary · context
    Patients were stratified by age ( 45 years) as a surrogate for clinically confirmed menopausal status.

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

  1. Version 2Current

    28 Oct 2026, 02:03 UTC

    Study results updated

  2. Version 1

    27 Oct 2026, 16:34 UTC

    First added · source update from Europe PMC

Subjects

Terms as the source lists them.

PepBank is a research reference. Talk to a doctor before you use any peptide.