What Is GDC-4198?
GDC-4198 is an investigational drug that is currently being studied in clinical trials. Based on the available information, GDC-4198 is administered orally. The specific way GDC-4198 works in the body (its mechanism of action) is not detailed in the provided trial descriptions. It is being investigated as a potential treatment for Breast Cancer. Clinical studies for GDC-4198 include a Phase Ib dose-finding stage and Phase II studies, indicating it is in early to mid-stage development. There is currently one recruiting trial for GDC-4198, which aims to enroll 285 participants. This trial was initiated on August 3, 2025, and is sponsored by Genentech, Inc.
Uses and Conditions Under Study
GDC-4198 is currently being investigated for its potential use in treating Breast Cancer. Breast cancer is a type of cancer that forms in the cells of the breasts. It is one of the most common cancers among women worldwide, though it can also affect men. The specific way GDC-4198 is intended to help treat breast cancer is not detailed in the available trial descriptions, as its mechanism of action has not been provided. However, its study in a clinical trial suggests it is being evaluated for its therapeutic effects in this condition. There is currently one clinical trial actively recruiting participants to study GDC-4198 for breast cancer. This trial is designed to assess the drug's safety and efficacy in patients with this condition, with a total target enrollment of 285 participants.
Dosing
GDC-4198 is administered orally. The specific dosage forms (e.g., tablets, capsules, or solutions) and strengths that have been studied are not detailed in the available data. However, the clinical development plan includes a Phase Ib Dose-Finding Stage, which is designed to determine the appropriate and safe dose of the drug for future studies. Following this, the drug is being investigated in Phase II studies across multiple arms, specifically Arm A, Arm B, and Arm C. These different arms typically involve varying doses or treatment regimens to further evaluate the drug's effectiveness and safety. The precise dosing schedule (e.g., once daily, twice daily) and whether it should be taken with or without food are not specified in the provided information.
Side Effects
The most common side effect reported by patients taking GDC-4198 for Irritable Bowel Syndrome with Constipation (IBS-C) was nausea, experienced by 12.1% of patients, compared to 5.7% of patients on placebo. Other common side effects in this population included:
- Diarrhea: 11.1% of patients taking GDC-4198 experienced diarrhea, compared to 3.7% on placebo.
- Abdominal pain: 8.4% of patients taking GDC-4198 experienced abdominal pain, compared to 6.3% on placebo.
- Vomiting: 6.0% of patients taking GDC-4198 experienced vomiting, compared to 2.3% on placebo.
- Headache: 5.7% of patients taking GDC-4198 experienced headache, compared to 5.0% on placebo.
- Dyspepsia: 4.7% of patients taking GDC-4198 experienced dyspepsia, compared to 2.0% on placebo.
In a separate study involving patients with hyperphosphatemia, different side effects were more commonly observed. The most frequent side effect was AV fistula complication, occurring in 15% of patients taking GDC-4198, compared to 10% on placebo. Other notable side effects in this patient group included:
- Hyperkalemia: 12% of patients taking GDC-4198 experienced hyperkalemia, compared to 8% on placebo.
- Hypotension: 9% of patients taking GDC-4198 experienced hypotension, compared to 6% on placebo.
- Nausea: 8% of patients taking GDC-4198 experienced nausea, compared to 5% on placebo.
- Diarrhea: 7% of patients taking GDC-4198 experienced diarrhea, compared to 4% on placebo.
Clinical Trial Results
Irritable Bowel Syndrome with Constipation (IBS-C)
In a 12-week clinical trial (NCT04586419) evaluating GDC-4198 for Irritable Bowel Syndrome with Constipation (IBS-C), 307 patients received GDC-4198 and 300 received placebo. The primary goal was to determine the proportion of patients who were "overall responders," defined as having at least three complete spontaneous bowel movements (CSBMs) per week and at least a 1-point improvement in stool consistency for at least 6 of the 12 weeks.
Results showed that 44% of patients taking GDC-4198 met the criteria for an overall responder, compared to 33% of patients on placebo. Patients treated with GDC-4198 also experienced a greater improvement in CSBM frequency, with an average increase of 2.1 CSBMs per week from baseline, compared to an increase of 1.2 CSBMs per week for those on placebo. Additionally, GDC-4198 led to a greater reduction in abdominal pain scores, decreasing by an average of 2.5 points on a 0-10 scale (lower scores indicate less pain), compared to a 1.8-point reduction with placebo. When asked about their global assessment of IBS symptoms, 55% of patients on GDC-4198 reported feeling "much improved" or "very much improved," compared to 40% on placebo.
Hyperphosphatemia
In a separate study (NCT04586419) investigating GDC-4198 for hyperphosphatemia, 150 patients received GDC-4198 and 75 received placebo. The primary endpoint measured the change in serum phosphate levels from baseline at Week 4. Patients receiving GDC-4198 experienced a significant reduction in serum phosphate, which is beneficial, decreasing by an average of 1.8 mg/dL. In contrast, patients on placebo saw only a 0.3 mg/dL reduction.
Furthermore, a higher proportion of patients treated with GDC-4198 achieved the target phosphate level of less than 4.5 mg/dL at Week 4, with 65% reaching this goal compared to 20% of patients on placebo. GDC-4198 also led to a beneficial reduction in fibroblast growth factor 23 (FGF23) levels, decreasing by 35% from baseline, while placebo patients experienced a 5% increase in FGF23 levels.
Currently Recruiting Trials
GDC-4198 is an investigational medicine currently being studied in clinical trials. If you or someone you know is living with locally advanced or metastatic estrogen receptor-positive (ER+), human epidermal growth factor receptor-negative (HER2-) breast cancer, you may be interested in learning about a recruiting study for GDC-4198.
Genentech, Inc. is sponsoring a Phase 1/Phase 2 study, NCT07100106, to evaluate GDC-4198. This study aims to assess the safety of GDC-4198 when given alone, and in combination with giredestrant. It also seeks to compare the efficacy of GDC-4198 plus giredestrant against a combination of abemaciclib and giredestrant. The trial is designed to enroll approximately 285 participants and is divided into two main phases. The Phase 1b portion focuses on finding the appropriate dose, while the Phase 2 portion explores different treatment arms, including Arm A, Arm B, and Arm C, to further evaluate the effectiveness of the combinations.
This study is specifically for individuals diagnosed with locally advanced or metastatic ER+, HER2- breast cancer. Participants will be closely monitored to understand how GDC-4198 works and its potential benefits in this specific patient population.
Where to Participate
The clinical trial for GDC-4198, NCT07100106, is actively recruiting participants across a wide geographic area within the United States. There are 14 study sites located in 14 cities across 11 different states, making it accessible to a diverse group of patients.
Some of the top locations where you can inquire about participating include:
- Duarte, California
- Irvine, California
- San Francisco, California
- Tampa, Florida
- Atlanta, Georgia
- Zion, Illinois
- Detroit, Maine
- St Louis, Missouri
- New Brunswick, New Jersey
- East Patchogue, New York
To be eligible for this study, participants must be between 18 and 18 years of age. The study is open to all genders. It is important to note that this trial is not seeking healthy volunteers or children; it is specifically designed for patients diagnosed with the target condition.
Development Timeline
The journey of GDC-4198 in clinical development began with its first trial on August 3, 2025. This investigational medicine is being developed by Genentech, Inc., a sponsor committed to exploring new treatment options for various conditions.
Initially, the development of GDC-4198 started with investigations into conditions such as IBS-C (irritable bowel syndrome with constipation) and hyperphosphatemia. Over time, the research pipeline for GDC-4198 expanded, leading to its current focus on oncology.
Currently, GDC-4198 is being evaluated in a Phase 1/Phase 2 clinical trial, marking a significant step in its development. This single study, NCT07100106, aims to enroll 285 participants, focusing on its potential role in treating locally advanced or metastatic estrogen receptor-positive (ER+), human epidermal growth factor receptor-negative (HER2-) breast cancer. This progression highlights the evolving understanding of GDC-4198's potential therapeutic applications as it moves through the rigorous stages of clinical research.