Plecanatide

Plecanatide is a near-copy of endogenous human uroguanylin, differing by one amino acid (aspartate substituted for glutamate at position 3) that improves stability while preserving uroguanylin's defining pH-dependent behaviour. It binds guanylate cyclase-C most avidly in the mildly acidic environment of the proximal duodenum and jejunum and loses activity as luminal pH rises distally. The resulting cGMP increase activates CFTR, moving chloride, bicarbonate and water into the lumen, and — as with linaclotide — extracellular cGMP reduces afferent nociceptor firing, which underlies its abdominal pain benefit in IBS-C. The pH-restricted profile is the design rationale for a somewhat lower diarrhoea rate, though head-to-head data against linaclotide are limited.

Targets: Guanylate cyclase-C (GC-C), CFTR chloride channel, cGMP-mediated afferent nociceptor modulation

• · 3 mg once daily is the only approved strength for both indications. Tablets may be crushed and mixed with applesauce or water if swallowing is difficult.

Work out your exact syringe units →

• commonDiarrhoea— Around 4-5% in trials, lower than linaclotide's roughly 20%, and the main reason for discontinuation.
• commonAbdominal distension and flatulence
• uncommonNausea
• rareSevere dehydration— Basis of the paediatric boxed warning; also possible in frail adults with persistent diarrhoea.

• Children under 6 years — boxed warning; risk of serious dehydration.
• Known or suspected mechanical gastrointestinal obstruction.
• Avoid in patients aged 6 to under 18 years.

• redundantlinaclotide — Same guanylate cyclase-C target; pick one.
• cautionosmotic-laxatives — Additive fluid loss with PEG, magnesium or lactulose.
• cautionproton-pump-inhibitors — Theoretically relevant, since plecanatide's activity is pH-dependent and PPIs raise proximal small bowel pH. Clinical significance has not been formally established.

• · Stool consistency and frequency; stop temporarily if severe diarrhoea develops.
• · Electrolytes if diarrhoea persists, particularly in older or frail patients.
• · Reassess abdominal pain benefit at 12 weeks in IBS-C.

FDA-approved (Trulance). Prescription-only. Not approved in the EU.

• Trulance (plecanatide) US prescribing information, Salix (label)
• Miner et al. 2017, plecanatide phase 3 in chronic idiopathic constipation, American Journal of Gastroenterology (trial)
• Brenner et al. 2018, plecanatide phase 3 in IBS-C (trial)

Plecanatide is a near-copy of endogenous human uroguanylin, and understanding uroguanylin explains everything distinctive about the drug. Uroguanylin is secreted by proximal small intestinal cells and is the acid-tolerant member of the guanylin family — it binds guanylate cyclase-C most avidly in mildly acidic conditions and loses activity as luminal pH rises. Guanylin, its sibling, is the opposite: it works in the more alkaline colon. Evolution built a pH-partitioned pair. Plecanatide preserves uroguanylin's pH dependence, which means its activity is concentrated in the proximal duodenum and jejunum and falls off distally. That pH restriction is the entire design rationale for the lower diarrhoea rate. Linaclotide, derived from a bacterial enterotoxin, is not strongly pH-dependent and acts throughout the bowel including the colon, where fluid secretion translates most directly into watery stool. Plecanatide front-loads its secretion into the proximal small bowel, where there is a long stretch of downstream intestine available to reabsorb any excess. The reported diarrhoea rates — roughly 4-5% versus linaclotide's roughly 16-20% — are consistent with that model, though they come from separate trial programmes rather than a head-to-head comparison. The single amino acid change from uroguanylin, Asp3 to Glu3, improves stability against proteolysis while preserving the pH-sensing behaviour. That is a very small edit for a marketed drug. Downstream the biology is identical to linaclotide: cGMP rises, protein kinase G II opens CFTR, chloride and bicarbonate move into the lumen with water following, and exported extracellular cGMP damps submucosal afferent nociceptor firing. The pain mechanism and its slow timescale are the same. Once again the bowel effect arrives in a day or two and the abdominal pain effect takes about twelve weeks. One practical consequence of the pH dependence deserves flagging: proton pump inhibitors raise proximal small bowel pH. Mechanistically that is exactly the environment in which plecanatide loses activity. Whether this matters clinically has never been formally established, but it is a real theoretical concern that does not apply to linaclotide.

The defining problem with plecanatide is that there is only one strength. If 3 mg gives you diarrhoea, there is no 1.5 mg. Your options are to stop, to dose on alternate days without any trial support for doing so, or to switch drugs. Linaclotide's three strengths are a genuine clinical advantage that gets underweighted when people compare these two on diarrhoea rates alone. The second is the boxed warning, which is stricter than linaclotide's: contraindicated under 6 years, and use should be avoided in patients aged 6 to under 18. That is a wider paediatric exclusion than linaclotide, which has a 72 mcg paediatric strength approved from age 6. The third is the PPI question. A very large fraction of people with functional GI complaints are on a proton pump inhibitor. Nobody has established what that does to a pH-dependent GC-C agonist, and it is plausible that some apparent plecanatide non-response is really PPI interference. The fourth is expectation mismatch on pain, identical to linaclotide: bowel effect in a day or two, abdominal pain effect over twelve weeks. People judge at week three. The fifth is desiccant handling — tablets are moisture-sensitive and belong in the original bottle, not a pill organiser.

1. 3 mgFrom day one, both indications — 3 mg once daily, with or without food, any time of day. This is the only approved strength for both chronic idiopathic constipation and IBS-C. There is no titration up and, critically, no titration down.
2. 3 mgIf swallowing is difficult — Tablets may be crushed and mixed with applesauce or water and taken immediately. Dose is unchanged.
3. —Week 12 — Reassess abdominal pain benefit in IBS-C at 12 weeks, which is the trial assessment window. If diarrhoea is the limiting problem, understand that with one strength your only real options are stopping or switching to linaclotide, which has three.

• Guanylate cyclase-C (GUCY2C), human — Listed as an agonist in the IUPHAR/BPS Guide to Pharmacology with no quantitative affinity value recorded. I could not resolve a published Ki or EC50, so none is asserted here.

  pH-dependent agonism at the apical enterocyte surface, maximal in the mildly acidic proximal duodenum and jejunum and falling off as luminal pH rises distally. This regional restriction is the defining pharmacological feature.

• CFTR chloride channel — Not a direct target.

  Opened downstream via cGMP and protein kinase G II, driving chloride, bicarbonate and water into the lumen.

• Extrinsic primary afferent nociceptors (submucosal) — Acted on by exported extracellular cGMP rather than by plecanatide itself.

  Reduced visceral pain fibre firing, underlying the abdominal pain benefit in IBS-C. Same slow 12-week timescale as linaclotide.

• Des-leucine plecanatide (active metabolite) — Not resolved.

  Formed in the gut by loss of the terminal leucine. Retains agonist activity; not measurable in plasma.

• A Randomized Phase III Clinical Trial of Plecanatide, a Uroguanylin Analog, in Patients With Chronic Idiopathic Constipation (Miner et al.) Phase 3 · n=1394 · 12 weeks · 2017

  Percentage of durable overall complete spontaneous bowel movement responders. Result: 21.0% on 3 mg and 19.5% on 6 mg versus 10.2% on placebo. The 6 mg arm added no benefit, which is why only 3 mg was marketed.

• Efficacy, safety, and tolerability of plecanatide in patients with irritable bowel syndrome with constipation: results of two phase 3 randomized clinical trials (Brenner et al.) Phase 3 · n=2189 · 12 weeks · 2018

  At least 30% reduction from baseline in worst abdominal pain plus an increase of at least one CSBM per week, in the same week, for at least 6 of 12 treatment weeks. Study 1: 30.2% (3 mg) and 29.5% (6 mg) versus 17.8% placebo. Study 2: 21.5% (3 mg) and 24.0% (6 mg) versus 14.2% placebo.

• Randomized clinical trial: efficacy and safety of plecanatide in the treatment of chronic idiopathic constipation (DeMicco et al.) Phase 3 · 12 weeks · 2017

  Durable overall CSBM responder rate in chronic idiopathic constipation. The second of the two pivotal CIC trials.

• Safety and tolerability of plecanatide in patients with chronic idiopathic constipation: long-term evidence from an open-label study (Barish et al.) Open-label extension · 2018

  Long-term safety and tolerability of plecanatide in chronic idiopathic constipation. The main source of extended-duration safety data for this drug.

First bowel movement commonly within 24-48 hours, slightly slower on average than linaclotide, which is consistent with the more proximal and pH-restricted site of action. Stool pattern stabilises over 1-2 weeks. Abdominal pain benefit in IBS-C accrues over 12 weeks, which is the trial assessment window and the point at which to decide. Constipation returns within days of stopping.

Do not combine with linaclotide. Same receptor, same downstream pathway, purely additive diarrhoea. Proton pump inhibitors are the interaction unique to this drug. Plecanatide's activity is pH-dependent by design and PPIs raise proximal small bowel pH. The clinical significance has never been formally established, but if you are on a PPI and plecanatide is not working, that is the first hypothesis to test — and if the PPI is non-negotiable, linaclotide is the more rational choice because it is not pH-restricted. Osmotic laxatives are additive on both fluid shift and electrolyte loss. Reduce the PEG or magnesium before adding plecanatide, not after. Diuretics plus secretory diarrhoea in an older adult is the combination that causes real harm. Have a rule for holding the diuretic. The practical advantage in stacking terms: because plecanatide has no food restriction and no timing requirement, it slots into a complicated medication schedule far more easily than linaclotide does. For someone already taking eight things at specific times, that is worth more than it sounds.

The plecanatide versus linaclotide decision comes down to three things. Diarrhoea: plecanatide is better. Roughly 4-5% versus roughly 16-20%, across separate trial programmes. The pH-restricted proximal site of action is a credible mechanistic explanation, not just a marketing claim. But there has never been an adequately powered head-to-head trial and cross-trial comparisons of adverse event rates are unreliable. Flexibility: linaclotide is better, and it is not close. Three strengths versus one. When diarrhoea does occur, linaclotide gives you somewhere to go. Convenience: plecanatide is better. Any time, with or without food, versus at least 30 minutes before the first meal. Efficacy on the primary endpoints looks broadly comparable in indirect comparison — linaclotide's IBS-C composite responder rate of 33.7% versus 13.9% placebo, plecanatide's 30.2% and 21.5% versus 17.8% and 14.2% across its two trials. Different placebo rates make even that comparison shaky. A reasonable heuristic: start with plecanatide if you are diarrhoea-prone, have a complicated dosing schedule, or cannot reliably dose before breakfast. Start with linaclotide if you want the option of dose adjustment, if you are on a PPI, or if you need a paediatric strength. Both of these, and teduglutide, sit in a different evidence universe from BPC-157 and KPV. Thousands of randomised patients and an FDA label is not the same kind of thing as a rodent colitis model.

A branded US prescription product (Trulance) with no generic at the time of writing and no EU approval. Real cost is dominated by insurance coverage. I did not verify a current price and will not invent one.

• ?No quantitative binding affinity for plecanatide at guanylate cyclase-C was resolvable — the Guide to Pharmacology entry records agonist action with no affinity value — so no number is asserted.
• ?No systemic PK parameters exist or can be calculated, per the label. All numeric PK fields are null accordingly.
• ?The claim that pH-restricted proximal activity causes the lower diarrhoea rate is the accepted mechanistic explanation but has not been demonstrated by a study isolating that variable.
• ?The diarrhoea rate comparison with linaclotide is cross-trial. No adequately powered head-to-head trial exists.
• ?The PPI interaction is theoretical. The label and literature acknowledge the pH dependence, but no clinical study has quantified whether acid suppression reduces plecanatide efficacy.
• ?The Core record states the substitution as 'aspartate substituted for glutamate at position 3'. The correct direction, per PubChem's description of plecanatide as (3-Glutamic acid(D>E))human uroguanylin, is glutamate substituted for aspartate. Worth correcting in Core.
• ?Enrolment figures for the DeMicco trial and the Barish open-label extension were not resolved and are left null.

• A Randomized Phase III Clinical Trial of Plecanatide, a Uroguanylin Analog, in Patients With Chronic Idiopathic Constipation Miner PB Jr, Koltun WD, Wiener GJ, et al., The American Journal of Gastroenterology, 2017 · PMID 28169285

  Pivotal CIC trial, 1394 patients. Note the flat dose-response between 3 mg and 6 mg — more is not better with this molecule either.

• Efficacy, safety, and tolerability of plecanatide in patients with irritable bowel syndrome with constipation: results of two phase 3 randomized clinical trials Brenner DM, Fogel R, Dorn SD, et al., The American Journal of Gastroenterology, 2018 · PMID 29545635

  The two pivotal IBS-C trials, 2189 patients combined, supporting the 2018 IBS-C approval.

• TRULANCE (plecanatide) tablets, US prescribing information Salix Pharmaceuticals, DailyMed / FDA label

  Source for the molecular formula C65H104N18O26S4, 1682 Da, the 4-12 and 7-15 disulfide pattern, the unquantifiable plasma levels, the des-leucine active metabolite, the absence of a food effect, and the diarrhoea rates (5% in CIC, 4.3% in IBS-C, both versus 1% placebo).

• Randomized clinical trial: efficacy and safety of plecanatide in the treatment of chronic idiopathic constipation DeMicco M, Barrow L, Hickey B, et al., Therapeutic Advances in Gastroenterology, 2017 · PMID 29147135

  The second pivotal CIC trial.

• Safety and tolerability of plecanatide in patients with chronic idiopathic constipation: long-term evidence from an open-label study Barish CF, et al., Current Medical Research and Opinion, 2018 · PMID 29343131

  Extended-duration safety, which matters for a drug taken indefinitely.