Glycyl-L-Tyrosine Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is supplied as a white to off-white crystalline powder. Two model designations are available: GlyTyr-PH-API-101 for oral solid-dose processing and GlyTyr-PH-API-201 for injectable and low-endotoxin manufacture. The anhydrous molecule has the formula C₁₁H₁₄N₂O₄ and a molecular weight of 238.24 g/mol; CAS 658-79-7. The manufacturing process is controlled under current good manufacturing practice with release specifications aligned to ICH Q6A decision-tree principles for synthetic peptides. In comparison with free L-tyrosine, which shows aqueous solubility of approximately 0.45 g/L at 25 °C, glycyl-L-tyrosine has a materially higher water solubility that permits both high-load oral solid forms and parenteral amino acid admixtures. Published saturation data for the dipeptide under all relevant pH and temperature conditions is limited; the downstream formulator should determine equilibrium solubility by the shake-flask method with HPLC quantitation according to Ph. Eur. 2.2.29 before fixing the commercial batch formula.

The dipeptide differs from free L-tyrosine and N-acetyl-L-tyrosine in three process-relevant respects. First, the dipeptide does not require alkaline pH adjustment for dissolution, reducing the risk of degradation in pH-sensitive fixed-dose combinations. Second, the impurity profile is dominated by peptide-related substances—free glycine, free L-tyrosine, and the diketopiperazine cyclization product—rather than acetylated by-products. Third, the oral and injectable grades are differentiated by particle size and endotoxin control, allowing the same molecular entity to be used across tablet, capsule, granule, and injection without changing the synthetic route. Direct substitution into an existing formula is not permissible without revalidation because bulk density, particle morphology, and moisture sorption behaviour are not equivalent to alternative amino acid sources.

Which analytical release limits apply to the pharma grade dipeptide?

Routine release uses a multi-method specification. The assay is determined by liquid chromatography against a qualified working standard, and the same method is used for related substances. The residual solvent profile is established by headspace gas chromatography with limits taken from ICH Q3C(R8). For parenteral applications, elemental impurity limits are set to the parenteral route concentration limits in ICH Q3D(R2), using the worst-case daily dose volume. The compliance matrix below summarizes the standard designations and typical release limits.

The specification is not limited to chemical purity. Physical attributes are determined because they control powder flow, segregation, and dissolution. Laser diffraction results are reported as D10, D50, and D90 values, and the method is validated according to ISO 13320-1:2020. Bulk density and tapped density are measured according to USP <616>; the Carr index is calculated from these values. A Carr index of 15–25% is considered acceptable for direct compression, while values above 30% indicate poor flow and require granulation or colloidal silicon dioxide addition at 0.25–0.5% w/w.

For oral solid-dose processing, bioburden is monitored because granulation water and excipient handling can introduce microbiological load. A 600 L bin blender operated at 12 rpm for 180 s after a pre-mix stage produces acceptable blend uniformity when the active fraction is at or above 10% w/w. For lower-dose strengths, a 5% w/w pre-mix with a portion of carrier improves assay uniformity and reduces discharge segregation. Tablet compression at 50–80 N hardness and capsule filling on dosator machines require consistent bulk density; batch-to-batch variation in tapped density is controlled within ±0.05 g/mL to avoid weight variation and content uniformity failure.

Particle-size and bulk-density controls for oral solid dose manufacture

The oral grade is not micronized to the same extent as the injectable grade because excessive fines can increase dusting, electrostatic adhesion, and capping tendency during tablet compression. The injectable grade is particle-size controlled to ensure rapid dissolution in Water for Injection. The comparison below defines the two model designations and their primary use.

Wet granulation trials at pilot scale have shown that addition of the oral grade during the dry-mix phase with intragranular disintegrant produces granules with final loss-on-drying 1.0–1.5% w/w after fluid-bed drying at inlet air 60 °C. At residual moisture above 2.0% w/w, tablet hardness increases but disintegration shifts beyond the 15 min limit described in USP <701> for uncoated tablets. At residual moisture below 0.5% w/w, granule friability rises and fines segregation appears at the tablet press feed frame. The moisture target is therefore treated as a critical process parameter during scale-up.

Powder bridging in the tablet press feed frame has been observed when tapped density falls below 0.35 g/mL, particularly in batches with D90 above 100 µm. Addition of 0.25% w/w colloidal silicon dioxide and control of residual moisture restored acceptable flow. For capsule filling, static charge build-up at low humidity caused powder adherence to dosator surfaces; maintaining 45–55% relative humidity and grounding the equipment eliminated the defect without reformulation.

When injectable manufacture is carried out by aseptic filtration

For parenteral products, the injectable grade is dissolved in Water for Injection at a concentration of 2.5–5.0% w/v and the solution pH is adjusted to 5.0–6.5 with 0.1 M hydrochloric acid or 0.1 M sodium hydroxide. The solution is passed through a 0.22 µm polyethersulfone or PVDF membrane under aseptic conditions and filled into Type I borosilicate glass vials with nitrogen overlay. Terminal sterilization at 121 °C for 15 min may be evaluated only after forced-degradation studies confirm that hydrolysis and diketopiperazine formation remain within specification at the chosen pH and fill volume. Aseptic filtration is preferred when the formula contains heat-labile excipients or when the required pH is outside the peptide stability window.

Particulate matter after final filtration is controlled according to USP <788> for small-volume parenterals: not more than 6000 particles ≥10 µm and 600 particles ≥25 µm per container. The fill line is qualified for filter compatibility, and the final dosage solution is held under nitrogen to limit oxidative discoloration. Published data for this specific configuration is limited; therefore, filter validation includes recovery studies for the API across the filter surface area and batch volume.

At production scale, filter flux decline can occur when solution concentration exceeds 5.0% w/v and product temperature falls below 15 °C. Preheating the bulk solution to 20–25 °C and using a 0.45 µm prefilter before the 0.22 µm sterilizing filter maintains line speed and reduces differential pressure excursions. The recirculation loop is operated at low shear to avoid foaming, and nitrogen overlay is maintained at 0.2 bar.

Impurity thresholds after reconstitution are governed by pH and temperature

In aqueous admixture, the principal degradation routes are peptide bond hydrolysis to free glycine and L-tyrosine, and cyclization to the corresponding diketopiperazine. The rate increases below pH 3 and above pH 7; the minimum is observed at approximately pH 5.5–6.5. Extemporaneous admixtures should be stored at 2–8 °C and used within 72 h unless stability data support a longer hold. Forced-degradation studies at 40 °C and 75% relative humidity are used to identify degradation products, but those conditions overstate the routine cold-chain hold time for injectable preparations.

Formulation incompatibilities include prolonged exposure to high-shear wet granulation at pH below 2 or above 10, which accelerates hydrolysis. Combination with strong oxidizers or peroxide-containing excipients is not recommended because the tyrosine phenol group can undergo oxidative coupling. Because the molecule contains a primary amine, prolonged wet granulation with reducing sugars under high heat can lead to Maillard browning; anhydrous fillers or non-reducing alternatives are preferred for moisture-sensitive granulations.

Granule dosage forms for oral administration are prepared by top-spray fluid-bed layering of the API onto mannitol or microcrystalline cellulose seed cores, using a 5% w/w aqueous binder solution of povidone K30. Inlet air temperature is maintained at 55–65 °C, product temperature at 30–35 °C, and spray rate is adjusted to keep final moisture at 1.0–1.5% w/w. The dried granules are sieved through a 0.8 mm screen and filled into stick packs or sachets. Dissolution testing in 900 mL purified water at 37 °C using USP <711> apparatus 2 at 50 rpm is used for product characterization, but release acceptance must be justified by batch data because there is no pharmacopeial dissolution monograph for this specific dipeptide.