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Study on the Effectiveness and Safety of Difelikefalin for Adults with Moderate-to-Severe Itching from Notalgia Paresthetica

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a condition called Notalgia Paresthetica, which causes moderate to severe itching in adults. The study will investigate the effectiveness and safety of a medication called Difelikefalin, which is taken orally in the form of a tablet. Difelikefalin works as a kappa-opioid receptor (KOR) agonist, which means it interacts with specific receptors in the body to help reduce itching sensations.

The purpose of the study is to evaluate how well Difelikefalin can reduce the intensity of itching in patients with Notalgia Paresthetica. The study is divided into two parts. In the first part, three different doses of Difelikefalin will be compared to a placebo to determine which dose is most effective. In the second part, the selected dose will be further tested to see how well it reduces itching over an 8-week period. Participants will take the medication daily, and their progress will be monitored throughout the study.

Participants will be assessed on various factors, including the improvement in their itching symptoms and any changes in skin sensations like burning or tingling. The study will also monitor any side effects that may occur during and after the treatment period. The goal is to find a safe and effective dose of Difelikefalin that can help alleviate the discomfort caused by Notalgia Paresthetica.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, eligibility is confirmed based on specific criteria, such as having moderate to severe itching due to notalgia paresthetica for at least six months.

    The presence of certain skin changes in the upper back area is also assessed.

  2. Step 2

    Part A: dose evaluation

    In this phase, different doses of difelikefalin are compared to a placebo to determine the most effective dose.

    The medication is taken orally in tablet form.

  3. Step 3

    Part B: efficacy assessment

    The selected dose from Part A is further evaluated for its effectiveness in reducing itch intensity over an 8-week period.

    The goal is to achieve a significant improvement in itch scores and assess changes in skin sensations.

  4. Step 4

    Medication administration

    Participants take the oral difelikefalin tablets as directed throughout the study duration.

    The frequency and dosage are determined based on the findings from Part A.

  5. Step 5

    Monitoring and assessments

    Regular assessments are conducted to monitor itch intensity, skin condition, and any changes in burning or tingling sensations.

    Safety evaluations are performed to track any adverse events during the study.

  6. Step 6

    End of treatment evaluation

    At the end of the 8-week treatment period, the effectiveness of the medication is evaluated based on the improvement in itch scores and skin condition.

    A follow-up period is included to assess any adverse events after treatment discontinuation.

Who can join the trial?

5 criteria

  • The patient must have **moderate to severe pruritus**. Pruritus is a medical term for itching.
  • The patient must have had chronic pruritus for at least **6 months** due to notalgia paresthetica (NP). Chronic means it has been ongoing for a long time.
  • The patient must have **changes in skin color** (either darker or lighter spots), **thickened skin**, **hardened skin**, and/or **scratches** in the middle to upper back near the shoulder blades.
  • The itching related to NP must be suitable for **systemic therapy**, which means treatment that affects the whole body, not just a specific area.
  • If the patient is a female, she must not be **pregnant or nursing** at any time during the study.

Who cannot join the trial?

9 criteria

  • Patients who have a history of severe allergic reactions to the study medication or similar drugs.
  • Patients who are currently participating in another clinical trial.
  • Patients with a medical condition that the study doctors believe could interfere with the study results.
  • Patients who are pregnant or breastfeeding.
  • Patients who have a history of drug or alcohol abuse within the past year.
  • Patients who have a significant mental health disorder that is not well controlled.
  • Patients who have a serious infection or illness that requires hospitalization.
  • Patients who have had major surgery within the past month.
  • Patients who are unable to follow the study procedures or instructions.
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Investigated drugs

Difelikefalin is an oral medication being studied for its ability to reduce moderate-to-severe itching in adults with a condition called notalgia paresthetica. The trial aims to find the most effective dose of this medication and assess how well it works in decreasing itch intensity over an 8-week treatment period.

What is already known about the treatment

Difelikefalin – Difelikefalin is administered orally and is currently being studied in clinical trials for its effectiveness in treating moderate-to-severe itching in adults with notalgia paresthetica. This medication is still under investigation, and its safety and efficacy are being evaluated in medical literature. It is primarily indicated for reducing itch intensity in this specific condition. At the molecular level, difelikefalin works by activating certain receptors in the body that help modulate the sensation of itch. It is classified pharmacologically as a kappa opioid receptor agonist.

Investigated diseases

Notalgia Paresthetica – Notalgia paresthetica is a chronic skin condition characterized by an intense itching sensation, typically located on the upper back. The itch is often accompanied by a burning or tingling sensation and may lead to skin changes such as hyperpigmentation due to persistent scratching. The exact cause is not well understood, but it is believed to be related to nerve irritation or compression. The condition tends to be persistent and can significantly affect quality of life due to the discomfort it causes. It is more common in adults and can vary in intensity, sometimes becoming more severe over time.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IVTrial ID2023-503957-36-00Protocol codeCR845-310601Estimated enrolment577 patientsSponsorCara Therapeutics Inc.

sourced from the EU Clinical Trials Register and site verification

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