Phase 1 · California
Phase 1 clinical trials in California
262 studies have at least one recruiting site in California. Phase 1 (and early Phase 1) trials are usually the first time a medicine is studied in people. They are typically small, closely monitored, and many are run in dedicated research units, sometimes with overnight stays.
262 recruiting studiesSource: ClinicalTrials.gov, refreshed October 26, 2026How we list studies
Studies
- RecruitingPhase 1
Evaluation of the Tolerability of Cagrilintide in Participants Not Tolerating GLP-1-RA Therapies Due to Gastrointestinal Adverse Events
Novo Nordisk A/S
- Location
- Walnut Creek, CA + 9 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1/Phase 2
DFT383 in Pediatric Participants With Nephropathic Cystinosis
Novartis Pharmaceuticals
- Location
- San Diego, CA + 5 other US sites
- Eligibility basics
- Ages 2–5
- RecruitingPhase 1
Obe-cel in Refractory Progressive Forms of Multiple Sclerosis
Autolus Limited
- Location
- Palo Alto, CA
- Eligibility basics
- Ages 18–60
- RecruitingPhase 1
An Early-Stage Study in Multiple Clinics of How Afimkibart May Affect the Body's Processing of Medicines That Rely on Cytochrome P450 Enzymes in Participants With Ulcerative Colitis
Hoffmann-La Roche
- Location
- Chula Vista, CA + 2 other US sites
- Eligibility basics
- Ages 18–60
- RecruitingPhase 1
Resmetirom in Patients With MASH and HFpEF
Madrigal Pharmaceuticals, Inc.
- Location
- Oxnard, CA + 4 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1
A Research Study Investigating How Adults With Overweight or Obesity, With or Without Type 2 Diabetes, Tolerate Switching to a New Treatment (Zenagamtide) From Their Current Semaglutide Medication
Novo Nordisk A/S
- Location
- Glendale, CA + 1 other US site
- Eligibility basics
- Ages 18+
- RecruitingPhase 1
A Research Study Investigating How Adults With Overweight or Obesity, With or Without Type 2 Diabetes, Tolerate Switching to a New Treatment (Zenagamtide) From Their Current Tirzepatide Medication
Novo Nordisk A/S
- Location
- Glendale, CA + 1 other US site
- Eligibility basics
- Ages 18+
- RecruitingPhase 1/Phase 2
A Phase 1/2, Open-label, Safety and Dosing Study of Autologous CART Cells (Desmoglein 3 Chimeric Autoantibody Receptor T Cells [DSG3-CAART] or CD19-specific Chimeric Antigen Receptor T Cells [CABA-201]) in Subjects With…
Cabaletta Bio
- Location
- Redwood City, CA + 9 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1
A Study to Learn About How Changing Therapy From Emicizumab to Marstacimab Affects People With the Severe Hemophilia A.
Pfizer
- Location
- Los Angeles, CA + 2 other US sites
- Eligibility basics
- Ages 12–74 · Men only
- RecruitingPhase 1/Phase 2
A Study to Investigate the Safety of OpCT-001 in Adults Who Have Primary Photoreceptor Disease (CLARICO)
BlueRock Therapeutics
- Location
- Los Angeles, CA + 4 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1/Phase 2
A Study in People With Diabetic Macular Edema to Test How Well Different Doses of BI 3812465 Are Tolerated
Boehringer Ingelheim
- Location
- Arcadia, CA + 24 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1
Study to Evaluate the Pharmacokinetics (PK), Safety and Tolerability up to 6 Years of Intravenous (i.v.) Secukinumab in Pediatric Participants With Juvenile Psoriatic Arthritis (JPsA).
Novartis Pharmaceuticals
- Location
- Loma Linda, CA + 10 other US sites
- Eligibility basics
- Ages 2–17
- RecruitingPhase 1
A Clinical Study of Letermovir (MK-8228) in Children and Adolescents Who Receive a Kidney Transplant (KT) (MK-8228-077)
Merck Sharp & Dohme LLC
- Location
- Los Angeles, CA + 20 other US sites
- Eligibility basics
- Up to age 17
- RecruitingPhase 1/Phase 2
A Gene Therapy Study of SPK-8011QQ in Adults With Severe or Moderately Severe Hemophilia A
Hoffmann-La Roche
- Location
- Orange, CA + 5 other US sites
- Eligibility basics
- Ages 18+ · Men only
- RecruitingPhase 1/Phase 2
A Study to Evaluate Safety, Tolerability, and Efficacy of AB-1009 Gene Therapy (GAA Gene) in Adult Participants With Late-Onset Pompe Disease (PROGRESS-GT LOPD)
AskBio Inc
- Location
- Irvine, CA + 4 other US sites
- Eligibility basics
- Ages 18–65
- RecruitingPhase 1/Phase 2
First-in-human Study of UX016 in GNEM
Ultragenyx Pharmaceutical Inc
- Location
- Orange, CA + 1 other US site
- Eligibility basics
- Ages 18–55
- RecruitingPhase 1
A Study to Investigate the Safety, Tolerability, and Pharmacokinetics of RO7663498 Following Intravitreal Administration in Participants With Diabetic Retinopathy
Hoffmann-La Roche
- Location
- Glendale, CA + 3 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1
A Phase 1 Study of LY5830966 in Participants With Primary Myelofibrosis (PMF), Post-Polycythemia Vera Myelofibrosis (PPV-MF), or Post-Essential Thrombocythemia Myelofibrosis (PET-MF) Who Have Been Failed by a Type I…
Ajax Therapeutics, Inc., a wholly owned subsidiary of Eli Lilly and Company
- Location
- Palo Alto, CA + 12 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1
A Trial to Test the Safety and Efficacy of TEV-53408 in Participants With Vitiligo
Teva Branded Pharmaceutical Products R&D LLC
- Location
- Fremont, CA + 2 other US sites
- Eligibility basics
- Ages 18–75
- RecruitingPhase 1/Phase 2
A Study of Pirtobrutinib in Participants With Immune Thrombocytopenia
Eli Lilly and Company
- Location
- Los Angeles, CA + 7 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1
Study to Evaluate the Maximal Use of Ruxolitinib Cream in Adult and Adolescent Participants With Hidradenitis Suppurativa
Incyte Corporation
- Location
- Northridge, CA + 15 other US sites
- Eligibility basics
- Ages 12–75
- RecruitingPhase 1
A Study to Evaluate the Safety, Tolerability, Pharmacodynamics, and Pharmacokinetics of RO7823653 in Participants With Diabetic Macular Edema (DME)
Genentech, Inc.
- Location
- Beverly Hills, CA + 11 other US sites
- Eligibility basics
- Ages 18+
- RecruitingPhase 1/Phase 2
A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of NXT007 in Persons With Severe or Moderate Hemophilia A
Hoffmann-La Roche
- Location
- Sacramento, CA + 2 other US sites
- Eligibility basics
- Ages 2–59 · Men only
- RecruitingPhase 1/Phase 2
ATTUNE: A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Intrathecally-Administered ION440 in Participants With Methyl CpG Binding Protein 2 (MECP2) Duplication Syndrome (MDS)
Ionis Pharmaceuticals, Inc.
- Location
- San Diego, CA + 7 other US sites
- Eligibility basics
- Ages 2–65 · Men only
Who these studies look for
Phase 1 studies often have narrow eligibility: specific age and weight ranges, no recent participation in another study, no nicotine, and limits on medications. Some Phase 1 studies recruit patients rather than healthy volunteers, so check each listing.
Matching a page like this one never means you qualify. Each research team decides eligibility at screening.
Questions
Are Phase 1 trials riskier?
Every study carries risk. Phase 1 studies involve less human data about the product, which is why they are closely monitored. The informed consent document explains the known risks; read it carefully and ask questions before signing.
Why do some Phase 1 studies include overnight stays?
Staying in the unit lets staff dose on a precise schedule and collect samples around the clock. Where a record mentions an inpatient stay we flag it on the listing.