TB500: Dosing Protocols

Research Dosing Disclaimer#

Clinical Trial Dosing Data#

Phase I Intravenous Safety Study#

The most rigorous human dosing data for Thymosin Beta-4 comes from a randomized, placebo-controlled phase I study by Allan and colleagues. This study enrolled 40 healthy volunteers across four ascending-dose cohorts:

All dose levels were well tolerated. Pharmacokinetic analysis showed dose-proportional increases in plasma Tβ4 concentrations with single doses, and the half-life increased with increasing dose. No dose-limiting toxicities were identified, and the maximum tolerated dose was not reached in this study.

Phase I Chinese Population Study#

A subsequent first-in-human study of recombinant human Thymosin Beta-4 in healthy Chinese volunteers confirmed the favorable safety profile with intravenous administration. Single ascending doses and multiple-dose cohorts were tested, with no serious adverse events at any dose level.

Dermal Wound Healing Trials#

In phase II clinical trials for venous stasis ulcers (NCT00832091) and pressure ulcers, Thymosin Beta-4 was administered as a topical gel formulation applied directly to the wound bed. The 0.03% concentration was used in the primary efficacy studies. Treatment continued until wound closure or the protocol-defined endpoint. In patients who responded to treatment, healing was accelerated by approximately one month compared to standard care.

Ophthalmic Clinical Trials#

RGN-259 (0.1% Thymosin Beta-4 ophthalmic solution) was tested in multiple clinical trials:

• Dry eye disease (Phase II): Twice-daily administration for 28 days demonstrated a 35.1% reduction in ocular discomfort and 59.1% reduction in corneal fluorescein staining versus vehicle control
• Neurotrophic keratopathy (Phase III): Twice-daily administration for 28 days promoted complete corneal healing in the majority of patients
• Compassionate use: In 6 patients with treatment-resistant neurotrophic keratopathy, 4 achieved complete healing by day 28, and the remaining 2 healed by days 55 and 60

Preclinical Dosing Data#

Wound Healing Models#

The foundational wound healing study by Malinda and colleagues (1999) used the following dosing protocols in a rat full-thickness punch wound model:

• Topical application: 6 micrograms of Tβ4 applied directly to the wound surface
• Intraperitoneal injection: 5 micrograms of Tβ4 administered IP

Both routes demonstrated significant efficacy, with re-epithelialization increased by 42% at day 4 and 61% at day 7 over saline controls. Subsequent studies in diabetic mice, aged mice, and steroid-treated rats used similar dosing approaches with consistent results.

Cardiac Models#

Preclinical cardiac studies have used various dosing protocols depending on the animal model:

• Mouse coronary artery ligation: 150 mg/kg IP (Bock-Marquette et al., 2004). Demonstrated activation of ILK-Akt survival pathway and improved cardiac function
• Pig myocardial ischemia-reperfusion: Systemic IV dosing before and after ischemia (Stark et al., 2016). Results showed no attenuation of injury in this large animal model, highlighting species-specific differences
• Rat models: Various doses ranging from 0.15 to 6 mg/kg have been tested across cardiac studies

Stroke Models#

In a dose-response study using an embolic stroke model in rats, three doses were compared:

• 2 mg/kg IP
• 12 mg/kg IP
• 18 mg/kg IP

The first dose was administered 24 hours after injury, followed by doses every 3 days for a total of 5 doses. The study established a dose-response relationship for neurological recovery endpoints.

Corneal Injury Models#

Topical administration of Tβ4 in corneal wound models typically used 0.1% solutions applied directly to the cornea multiple times daily. In the alkali injury model by Sosne and colleagues (2002), Tβ4 was applied topically to mouse corneas following sodium hydroxide exposure, demonstrating accelerated re-epithelialization and decreased inflammatory cell infiltration at all time points.

Allometric Scaling Considerations#

When extrapolating animal doses to potential human doses, allometric scaling principles should be applied. Simple weight-based scaling is generally inappropriate for peptides, and body surface area (BSA) normalization is preferred. The human equivalent dose (HED) from mouse studies uses a conversion factor of 12.3 (divide mouse dose in mg/kg by 12.3):

The phase I clinical trial doses (42-1260 mg, approximately 0.6-18 mg/kg for a 70 kg adult) provide the most relevant human dosing reference.

Reconstitution and Preparation#

Materials Needed#

• TB500 lyophilized vial (typically 2 mg or 5 mg)
• Bacteriostatic water for injection (preserved with 0.9% benzyl alcohol)
• Alcohol swabs for aseptic technique
• Sterile syringe and needle (25-30 gauge for reconstitution, 27-31 gauge for subcutaneous injection)

Reconstitution Procedure#

1. Remove caps from the TB500 vial and bacteriostatic water vial
2. Swab both rubber stoppers with alcohol and allow to dry
3. Using a sterile syringe, draw up the desired volume of bacteriostatic water
4. Insert the needle into the TB500 vial, directing the stream of water against the glass wall rather than directly onto the lyophilized powder
5. Allow the water to flow gently down the vial wall into the powder
6. Gently swirl the vial until the powder is completely dissolved (do not shake vigorously, as this can cause peptide degradation through shear stress and foaming)
7. Inspect the solution: it should be clear and colorless with no visible particulates
8. Label the vial with the reconstitution date, concentration, and storage instructions

Concentration Examples#

Administration Routes#

Subcutaneous Injection#

Subcutaneous injection is the most commonly referenced route in non-clinical research protocols. The injection is administered into the fatty tissue beneath the skin using a short, fine-gauge needle (27-31 gauge, 0.5 inch length). Common injection sites include the abdominal area (avoiding a 2-inch radius around the navel), the anterior thigh, and the upper arm. Injection sites should be rotated to prevent lipodystrophy or localized tissue irritation.

Intravenous Administration#

Intravenous administration was the route used in phase I clinical trials. This route provides 100% bioavailability and immediate systemic distribution but requires trained personnel and sterile IV access. It is not practical for non-clinical settings.

Topical Application#

Topical formulations have been used in both dermal wound healing trials (0.03% gel) and ophthalmic trials (0.1% solution). This route provides localized delivery to the target tissue with minimal systemic exposure.

Storage Guidelines#

Proper storage is essential for maintaining TB500 peptide integrity:

Lyophilized (Unreconstituted) Form#

• Optimal: -20 degrees Celsius (freezer), protected from light and moisture
• Acceptable: 2-8 degrees Celsius (refrigerator) for shorter-term storage
• Shelf life: Typically stable for 2+ years at -20C; check manufacturer specifications
• Do not: Store at room temperature for extended periods

Reconstituted Solution#

• Required: 2-8 degrees Celsius (refrigerator)
• Shelf life: Use within 14-28 days of reconstitution
• Do not: Freeze reconstituted solution (causes irreversible aggregation)
• Do not: Leave at room temperature for prolonged periods
• Protect: From direct light exposure (Met-6 is light-sensitive)
• Discard if: Cloudy, discolored, or containing visible particles

Travel and Transport#

If transport is necessary, use a cold pack or insulated container to maintain 2-8 degrees Celsius. Avoid exposure to extreme temperatures or direct sunlight during transport.

Evidence Gaps in Dosing#

• No human dose-optimization studies have established the ideal dose for any specific indication
• Subcutaneous bioavailability has not been formally characterized in humans
• The dose-response relationship for different tissue types (dermal, cardiac, corneal) has not been systematically compared
• Optimal duration of treatment for various applications is unknown
• The pharmacokinetic impact of different injection sites has not been studied
• No studies have compared the efficacy of the full-length Tβ4 peptide versus the TB-500 fragment at equivalent molar doses
• Timing of administration relative to injury (immediate vs. delayed) has not been optimized across indications

Related Reading#

• TB500 overview and research guide
• TB500 side effects profile
• TB500 research evidence