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RecruitingLast updated: 19 January 2026

KAT6: Targeted therapy (PF-07248144) when given alone or in combination with other treatments for the treatment of breast cancer, prostate cancer, or lung cancer that is locally advanced or metastaticA Phase 1 Dose Escalation and Expansion Study to Evaluate Safety, Tolerability, Pharmacokinetic, Pharmacodynamic, and Anti-tumor Activity of PF-07248144 in Participants With Advanced or Metastatic Solid Tumors.

Trial purpose

Medical clipboardCancer treatment

Tumor type

Multi-Cancer Multi-Cancer

Age

People18+

Trial acronym

KAT6

Clinical summary

Summary

You may be eligible for this study if you have locally advanced o rmetastatic ER+, HER2- breast cancer, castration resistant prostate cancer or non-small cell lung cancer. Specific prior treatment history is required for each part of the study - speak to your doctor about whether you may be eligible.

This study is focused on finding on safety and finding the right dose of PF-07248144 when given by itself and in combination with other treatments. The study has two parts: Part 1 (Dose Escalation) and Part 2 (Dose Expansion).

Part 1
This part is divided into three parts - 1A, 1B and 1C.

  • Part 1A: Participants receive increasing doses of PF-07248144 alone. The goal is to find the maximum tolerated dose (MTD) and determine the recommended phase 2 dose (PR2D) for the monotherapy.
  • Parts 1B and 1C: PF-07248144 is given together with other treatments - either fulvestrant hormone therapy (Part 1B) or letrozole hormone therapy plus palbociclib targeted therapy (Part 1C). These parts aim to identify the safe and effective dose for each combination.

Part 2
This part is divided into two parts - 2A and 2B.

  • Part 2A: Once the monotherapy RP2D is identified in Part 1A, PF-07248144 will be tested at this dose in a larger group to further assess safety and early signs of benefit.
  • Part 2B: After safe doses for the combination treatments are identified in Parts 1B and 1C, one or both combinations may move forward into expansion in Part 2B. The decision about which combinations continue will be based on preclinical findings, safety results, early signs of effectiveness, and how the drug is handled by the body.

Conditions

This trial is treating people with Non-small cell lung cancer, castration-resistant prostate cancer, and ER+, HER2- breast cancer

Eligibility

Inclusion

  • Disease Characteristics - Breast, Prostate, and Lung Cancer
  • Part 1A (Monotherapy Dose Escalation) Histological or cytological diagnosis of locally advanced or metastatic ER+HER2- breast cancer, CRPC, or NSCLC that is intolerant or resistant to standard therapy or for which no standard therapy is available.
  • Part 1B, Part 1C, Part 1D and Part 1E (Combination Dose Escalation) Histological or cytological diagnosis of locally advanced or metastatic ER+HER2- breast cancer. Participants must have progressed after at least 1 prior line of treatment with an endocrine therapy and CDK4/6 inhibitor in the advanced or metastatic setting.
  • Part 2A (ER+HER2- breast cancer 2L+, monotherapy) Histological or cytological diagnosis of locally advanced or metastatic ER+HER2- breast cancer. Participants must have progressed after at least 1 prior line of CDK4/6 inhibitor and 1 line of endocrine therapy.
  • Part 2B (ER+HER2- breast cancer 2-4L, combination with fulvestrant) Histological or cytological diagnosis of advanced or metastatic ER+HER2- breast cancer. Participants must have progressive disease after at least 1 prior line of a CDK4/6 inhibitor and at least 1 prior line of endocrine therapy.. Participants must not have received more than 3 prior lines of systemic therapies including up to 1 line of cytotoxic chemotherapy for visceral disease in advanced or metastatic setting; Participants may have but are not required to have prior treatment with fulvestrant.
  • Part 2D (ER+HER2- breast cancer 2-4L, combination with PF-07220060 (CDK4i) and fulvestrant):

Histological or cytological diagnosis of advanced or metastatic ER+HER2- breast cancer. Participants must have progressive disease after at least 1 prior line of a CDK4/6 inhibitor and at least 1 prior line of endocrine therapy.

  • Participants must have not received more than 3 lines of systemic therapies including up to 1 line of cytotoxic chemotherapy for visceral disease in advanced or metastatic setting; Participants may have but are not required to have prior treatment with fulvestrant.
  • Part 2E (ER+HER2- breast cancer 2-4L, combination with vepdegestrant): Histological or cytological diagnosis of advanced or metastatic ER+HER2- breast cancer. Participants must have progressive disease after at least 1 prior line of a CDK4/6 inhibitor and at least 1 prior line of endocrine therapy; Participants must have not received more than 3 lines of systemic therapies including up to 1 line of cytotoxic chemotherapy for visceral disease in advanced or metastatic setting; Participants may have received fulvestrant
  • Participants with ER+HER2- advanced or metastatic breast cancer must have documentation of ER-positive tumor (≥1% positive stained cells) based on most recent tumor biopsy utilizing an assay consistent with local standards.
  • Participants with ER+HER2- advanced or metastatic breast cancer must have documentation of HER2-negative tumor: HER2-negative tumor is determined as immunohistochemistry score 0/1+ or negative by in situ hybridization (FISH/CISH/SISH/DISH) defined as a HER2/CEP17 ratio <2 or for single probe assessment a HER2 copy number <4.
  • Female participants with ER+HER2- advanced or metastatic breast cancer considered to be of childbearing potential (or have tubal ligations only) must be willing to undergo medically induced menopause by treatment with the approved LHRH agonist such as goserelin, leuprolide or equivalent agents to induce chemical menopause.
  • Female participants with ER+HER2- advanced or metastatic breast cancer of nonchildbearing potential must meet at least 1 criteria of achieving postmenopausal status.
  • Participants must have at least 1 measurable lesion as defined by RECIST version 1.1 that has not been previously irradiated.
  • Eastern Cooperative Oncology Group (ECOG) Performance Status PS 0 or 1
  • Female or male patients aged ≥ 18 years (Japan ≥ 20 years) (South Korea ≥ 19 years).
  • Adequate renal, liver, and bone marrow function.
  • Resolved acute effects of any prior therapy to baseline severity or CTCAE Grade 1 except for adverse events (AEs) not constituting a safety risk by investigator judgment.

Exclusion

  • Unmanageable ascites (limited medical treatment to control ascites is permitted, but all participants with ascites require review by sponsor's medical monitor).
  • Participants with any other active malignancy within 3 years prior to enrollment, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ.
  • Major surgery, radiation therapy, or systemic anti-cancer therapy within 3 weeks prior to study entry.
  • Prior irradiation to >25% of the bone marrow.
  • ECG clinically relevant abnormalities (eg, QTc >470 msec, complete LBBB, second/third degree AV block, ST elevation or EKG changes suggesting myocardial infarction or active myocardia ischemia).
  • Therapeutic anticoagulation. However, low molecular weight heparin is allowed. Vitamin K antagonists or factor Xa inhibitors may be allowed following discussion with the Sponsor.
  • Known or suspected hypersensitivity or severe allergy to active ingredient/excipients of PF-07248144.
  • Active inflammatory GI disease, refractory and unresolved chronic diarrhea or previous gastric resection, lap band surgery or other GI conditions and surgeries that may significantly alter the absorption of PF-07248144 tablets. Gastroesophageal reflux disease under treatment is allowed.
  • Pregnant or breastfeeding female participants.

Inclusion

  • Your cancer has spread to other parts of the body (metastatic) or has grown into nearby parts of the body (locally advanced).
  • Your cancer has not spread to other parts of the body, but it is not possible to perform surgery to remove it (unresectable).
  • You have had treatment but your cancer has gotten worse or has not responded to the treatment you have been given.

Exclusion

  • You have been diagnosed with a prior or secondary type of cancer.
  • You have certain types of non-cancer medical conditions.
  • You have had certain treatments, surgical procedures or drugs.
Message

Clinical trials have complex eligibility criteria, and other criteria may apply for this trial. Ask your doctor about whether this trial could be right for you.

Participating hospitals

Recruiting hospitals

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More information

Trial Identifiers

Information on this page is partially produced from ClinicalTrials.gov *. View further details about this trial on the registry via the links below:

Trial sponsor

Pfizer

Scientific Title

A Phase 1 Dose Escalation and Expansion Study to Evaluate Safety, Tolerability, Pharmacokinetic, Pharmacodynamic, and Anti-tumor Activity of PF-07248144 in Participants With Advanced or Metastatic Solid Tumors.

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