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Study on Pembrolizumab and Paclitaxel for Advanced Hormone Receptor-Positive, HER2-Negative Breast Cancer in Patients Resistant to CDK 4/6 Inhibitors

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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 type of breast cancer known as hormone receptor-positive/HER2-negative advanced or metastatic breast cancer. This type of cancer is resistant to standard hormone treatments. The study is testing a new treatment combination that includes the drug pembrolizumab, also known by its code name MK-3475, and another medication called paclitaxel. Pembrolizumab is a type of immunotherapy, which means it helps the body's immune system fight cancer cells. Paclitaxel is a chemotherapy drug that works by stopping cancer cells from growing and dividing.

The purpose of the study is to evaluate how effective this combination of treatments is for patients whose cancer has progressed after previous treatments. Participants in the study will receive the treatment through an intravenous infusion, which means the medication is given directly into a vein. The study will monitor the participants over a period of time to see how their cancer responds to the treatment. This includes looking for signs of the cancer shrinking or stopping its growth, as well as checking for any side effects from the treatment.

The study will also collect information on how long the treatment keeps the cancer from getting worse and how long patients live after starting the treatment. This information will help researchers understand the potential benefits and risks of using pembrolizumab and paclitaxel together for this type of breast cancer. The study aims to provide new insights into treatment options for patients with advanced breast cancer who have limited options after standard therapies have failed.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment

    Upon joining the study, an initial assessment is conducted to confirm eligibility. This includes a review of medical history and current health status.

    A sample of tumor tissue is required for PAM50 analysis to determine the subtype of breast cancer. This analysis helps in identifying the non-luminal subtype, such as HER2-enriched or basal-like.

  2. Step 2

    Treatment initiation

    The treatment phase begins with the administration of pembrolizumab and paclitaxel. Pembrolizumab is given as an intravenous infusion, which means it is delivered directly into the bloodstream through a vein.

    The dosage and frequency of administration are determined by the study protocol and are monitored by healthcare professionals.

  3. Step 3

    Ongoing monitoring

    Regular monitoring is conducted to assess the response to treatment. This includes physical examinations, imaging tests, and laboratory tests to evaluate the overall response rate (ORR) and other health indicators.

    The response is measured using criteria known as RECIST, which helps in determining the size and progression of tumors.

  4. Step 4

    Evaluation of treatment response

    The effectiveness of the treatment is evaluated based on the overall response rate, which includes complete response (CR) or partial response (PR).

    Secondary outcomes such as clinical benefit rate, progression-free survival, and overall survival are also assessed to understand the impact of the treatment over time.

  5. Step 5

    Completion of treatment

    The treatment phase continues until the study's end date or until the disease progresses, as determined by the healthcare team.

    Upon completion, a final assessment is conducted to document the outcomes and any changes in health status.

Who can join the trial?

16 criteria

  • Participants must be at least 18 years old.
  • Participants must have a confirmed diagnosis of locally advanced or metastatic breast cancer that is hormone receptor positive (meaning the cancer grows in response to hormones) and HER2-negative (a type of protein not present in the cancer).
  • Participants must have cancer that cannot be treated with surgery.
  • Participants can have had prior radiation therapy for metastatic disease, but at least 2 weeks must have passed since the last dose, or they must have recovered from its effects.
  • The cancer must be resistant to CDK4/6 inhibitors, which means the cancer returned or progressed during or shortly after treatment with these drugs.
  • Participants may have had previous chemotherapy with a taxane (a type of cancer drug) for early breast cancer.
  • A sample of the tumor tissue must be available for testing, and it must be of good quality.
  • The cancer must be of a non-Luminal subtype based on specific testing (PAM50 analysis).
  • Participants must have an ECOG performance status of 0 to 1, which means they are fully active or have some symptoms but do not need bed rest.
  • Participants must have a life expectancy of at least 12 weeks.
  • The cancer must be measurable according to specific criteria (RECIST v1.1).
  • Participants must have adequate blood and organ function based on recent laboratory tests.
  • Male participants must agree to use contraception during the study and for a period after the last dose of treatment.
  • Female participants must not be pregnant or breastfeeding and must agree to use contraception if they are of childbearing potential.
  • Participants must be eligible for taxane therapy.
  • Participants must not have had prior chemotherapy for inoperable locally advanced or metastatic breast cancer.

Who cannot join the trial?

5 criteria

  • Patients who have a different type of breast cancer than the one being studied.
  • Patients who have not shown resistance to hormone therapy for their breast cancer.
  • Patients who are not women, as the study is focused on women only.
  • Patients who are not in the age range specified for the study.
  • Patients who are considered part of a vulnerable population, which means they might need special protection or care.
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Investigated drugs

  • Pembrolizumab

    is a type of immunotherapy that helps the body's immune system fight cancer. It works by blocking a specific protein on cancer cells, allowing the immune system to better recognize and attack these cells.

  • Paclitaxel

    is a chemotherapy drug that interferes with the growth of cancer cells. It works by stopping the cells from dividing, which can slow or stop the spread of cancer.

What is already known about the treatment

  • Pembrolizumab

    This medication is administered intravenously and is currently being studied in clinical trials for its effectiveness in treating certain types of breast cancer. It is primarily used for patients with advanced or metastatic hormone receptor-positive, HER2-negative breast cancer that is resistant to endocrine therapy. Pembrolizumab works by blocking a protein called PD-1 on immune cells, which helps the immune system recognize and attack cancer cells. It is classified as an immune checkpoint inhibitor.

  • Paclitaxel

    This medication is also administered intravenously and is well-established in medical practice for treating various cancers, including breast cancer. It is used in combination with other drugs for patients with advanced or metastatic hormone receptor-positive, HER2-negative breast cancer. Paclitaxel works by inhibiting cell division, which prevents cancer cells from growing and spreading. It is classified as a mitotic inhibitor.

Investigated diseases

Breast Cancer, Hormone Receptor-Positive/HER2-Negative – This type of breast cancer is characterized by the presence of hormone receptors but lacks overexpression of the HER2 protein. It can occur in both pre and post-menopausal women and may become resistant to endocrine therapy over time. The disease can be locally advanced, meaning it has spread beyond the breast to nearby tissues, or metastatic, indicating it has spread to distant parts of the body. As the cancer progresses, it may become more challenging to manage due to its resistance to standard hormone therapies. The progression is often monitored using criteria that assess tumor size and spread.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-508546-17-00Protocol codeSOLTI-1716Estimated enrolment46 patientsSponsorSolti Group

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