First-in-Human Study Testing a New Antibody Treatment for Tick-Borne Encephalitis in Healthy Volunteers. (SVRI01)

A Phase I Study to Investigate the Safety, Tolerability, and Pharmacokinetic Characteristics of Intravenous (IV) Administration of a Human Monoclonal Antibody Against Tick-borne Encephalitis Virus in Healthy Adults.

The goal of this clinical trial is to evaluate the safety, tolerability, and pharmacokinetics of the investigational monoclonal antibody TBE025 when given intravenously to healthy adult volunteers aged 18 to 55.

The study aims to determine the recommended Phase II dose of TBE025 and to assess the incidence and severity of adverse events related to its administration.

There is no comparison group, as this is a single-arm, open-label study. Participants will receive a single intravenous infusion of TBE025 at one of three escalating dose levels, will be monitored for safety with regular clinical and laboratory assessments, and will provide blood samples for pharmacokinetic, anti-drug antibody, and neutralization testing.

Study Overview

• Status: Not yet recruiting
• Conditions: The Tick-borne Encephalitis Virus (TBEV)
• Intervention / Treatment: Drug: Human monoclonal antibody TBE025, intravenous infusion

Detailed Description

The tick-borne encephalitis virus (TBEV) is an infection spread by ticks that is becoming more common in Europe, including Switzerland. Currently, there is no specific treatment-care focuses on relieving symptoms. Vaccines exist, but few people get vaccinated, and sometimes the vaccine does not offer full protection. There is therefore a real need for new ways to prevent or treat this disease.

TBE025 is a fully human antibody taken from people who have recovered from TBEV. It can strongly block the virus. In lab studies with mice, TBE025 was able to protect against infection, both when given before exposure and soon after infection. It also appears to be safe, with no harmful effects on other tissues.

This first-in-human study (phase 1) will evaluate intravenous administration of TBE025 in healthy adult volunteers using a standard 3+3 dose-escalation design (200 mg, 600 mg, 2000 mg). Between 3 and 18 participants will be enrolled sequentially across three cohorts. The study is designed to establish the maximum tolerated dose and recommended Phase II dose, as well as to characterize the pharmacokinetics, immunogenicity, and neutralization capacity of TBE025.

Participants will be followed for safety, laboratory, and pharmacokinetic assessments over a three-month period. The study will provide the first clinical data on TBE025 in humans and will inform the design of subsequent efficacy trials in populations at risk of TBEV infection.

• Study Type: Interventional
• Enrollment (Estimated): 18
• Phase: Phase 1

Contacts and Locations

• Study Contact: Name: Laura Molinari; Phone Number: +41795560626; Email: laura.molinari@chuv.ch

Study Locations

• Switzerland
  • Canton of Vaud
    • Lausanne, Canton of Vaud, Switzerland, 1011
      • Centre Universitaire Hospitalier Vaudois (CHUV)

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adults aged 18 to <55 years
• Good general health (medical history, physical exam, normal labs)
• Written informed consent provided
• Ability to read and understand local language
• Contraception requirements : Women of childbearing potential: negative pregnancy test, surgically sterile, postmenopausal, or using highly effective contraception for 3 months post-infusion. Men: surgically sterile or using highly effective contraception (self or partner) and abstain from sperm donation for 3 months post-infusion.

Exclusion Criteria:

• BMI <19 or >30
• Infections: HIV, active hepatitis B (HBsAg), active hepatitis C
• Prior participation in investigational study within 30 days
• History of hypersensitivity to monoclonal antibodies
• Recent surgery or unresolved adverse events
• Active autoimmune disease requiring systemic treatment
• Recent use of immunosuppressive agents or immunoglobulins
• Immunodeficiency diagnosis
• Significant cardiovascular events within 6 months
• Live/attenuated vaccines within 28 days
• Major surgery within 28 days
• Pregnancy or breastfeeding
• Professional or private link with the research team
• Any condition judged by the investigator to interfere with safety or study results

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Sequential Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cohort 1; TBE025 200 mg administered intravenously on Day 0	Drug: Human monoclonal antibody TBE025, intravenous infusion; TBE025 is a recombinant, fully human monoclonal antibody (mAb). It is provided in single-use vials containing 20 mg/mL of protein in 5 mL of buffered solution consisting of 10 mM Histidine, 250 mM Trehalose, 10 mM Methionine, 0.05% Polysorbate 20 and water for injection, at pH 5.5. TBE025 is a clear to opalescent, colorless to brown liquid.
Experimental: Cohort 2; TBE025 600 mg administered intravenously on Day 0	Drug: Human monoclonal antibody TBE025, intravenous infusion; TBE025 is a recombinant, fully human monoclonal antibody (mAb). It is provided in single-use vials containing 20 mg/mL of protein in 5 mL of buffered solution consisting of 10 mM Histidine, 250 mM Trehalose, 10 mM Methionine, 0.05% Polysorbate 20 and water for injection, at pH 5.5. TBE025 is a clear to opalescent, colorless to brown liquid.
Experimental: Cohort 3; TBE025 2000 mg administered intravenously on Day 0	Drug: Human monoclonal antibody TBE025, intravenous infusion; TBE025 is a recombinant, fully human monoclonal antibody (mAb). It is provided in single-use vials containing 20 mg/mL of protein in 5 mL of buffered solution consisting of 10 mM Histidine, 250 mM Trehalose, 10 mM Methionine, 0.05% Polysorbate 20 and water for injection, at pH 5.5. TBE025 is a clear to opalescent, colorless to brown liquid.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximum Tolerated Dose (MTD) of TBE025	Number and percentage of subjects experiencing AEs, SAEs, AEs related to investigational product at each dose level	Up to 84 days after the infusion
Incidence and severity of adverse events (AEs)	Number and percentage of subjects experiencing AEs related to investigational product and the severity of the AEs at each dose level	Up to 84 days after the infusion
Incidence and severity of Dose Limiting Toxicity (DLT)	Number and percentage of participants experiencing DLTs at each dose level.	Up to 21 days after the infusion.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pharmacokinetic profile of TBE025	Plasma concentration measured by ELISA for each participant at each dose level	up to 84 days after infusion
Presence of anti-drug antibodies	Antibodies against TBE025 measured by ELISA for each participant at each dose group	Up to 84 days after infusion

Collaborators and Investigators

• Sponsor: Giuseppe Pantaleo
• Collaborators: Rockefeller University

Study record dates

Study Major Dates

• Study Start (Estimated): January 1, 2026
• Primary Completion (Estimated): May 31, 2026
• Study Completion (Estimated): October 31, 2026

Study Registration Dates

• First Submitted: November 18, 2025
• First Submitted That Met QC Criteria: January 22, 2026
• First Posted (Actual): January 29, 2026

Study Record Updates

• Last Update Posted (Actual): January 29, 2026
• Last Update Submitted That Met QC Criteria: January 22, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: Healthy volunteers; Monoclonal antibody; Phase I clinical trial; Intravenous administration; Tick-borne encephalitis; Tick-borne encephalitis virus; Human antibody therapy
• Additional Relevant MeSH Terms: Infectious Encephalitis; Vector Borne Diseases; Neuroinflammatory Diseases; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Infections; RNA Virus Infections; Virus Diseases; Arbovirus Infections; Flavivirus Infections; Flaviviridae Infections; Tick-Borne Diseases; Encephalitis, Viral; Central Nervous System Viral Diseases; Central Nervous System Infections; Encephalitis; Encephalitis, Arbovirus; Encephalitis, Tick-Borne; Therapeutics; Drug Administration Routes; Drug Therapy; Administration, Intravenous; Infusions, Parenteral; Infusions, Intravenous
• Other Study ID Numbers: SVRI01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: No individual participant data (IPD) will be shared. Only de-identified subject-level data may be provided if requested, and only in accordance with participant informed consent and applicable laws.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes