Lenacapavir pharma grade active pharmaceutical ingredient is supplied as two cGMP presentations: model LP-FA, the free acid with CAS 2189684-44-2, and model LP-Na, the sodium salt with CAS 2283356-12-5. Both presentations are controlled for identity by X-ray powder diffraction, residual solvents by headspace gas chromatography, and elemental impurities by inductively coupled plasma mass spectrometry. The molecule is a first-in-class HIV-1 capsid inhibitor; its interaction with the capsid hexamer alters both assembly and disassembly, a mechanism distinct from reverse transcriptase, integrase, and protease inhibitors. Because no harmonized USP or Ph. Eur. monograph is available for lenacapavir at the time of writing, the release specification is anchored to ICH Q6A, ICH Q3C, ICH Q3D, and the marketing authorization holder’s chemistry, manufacturing, and controls file. The free acid is used for oral tablet, capsule, and granule development; the sodium salt is used for aqueous injectable processing where higher aqueous solubility at physiologically compatible pH is required. The API is available as a dry powder, not as a formulated ready-to-use dosage form.

Why Does Solid-State and Particle-Size Control Determine Granulation Behaviour?

For oral tablet and capsule development, the free acid is rarely suitable for direct compression because the cohesive fines increase the Hausner ratio above 1.35 and reduce bulk density below 0.30 g/mL. Wet granulation or roller compaction is therefore used to enlarge the particle size and improve flow. A high-shear granulator with impeller tip speed of 2.5–6.0 m/s and powder-bed moisture of 12–18% w/w produces wet mass that is screened through a 1.25 mm mesh and dried in a fluid-bed dryer to a loss on drying of ≤1.5%. Lubrication is performed with magnesium stearate at 0.5–1.0% w/w for 3–5 minutes; blending beyond 5 minutes may increase tablet disintegration time and reduce dissolution. The dried granules are compressed on a rotary tablet press with precompression force of 4–8 kN and main compression force of 12–22 kN. Tablet hardness is measured by USP <1217> and maintained between 80–120 N to avoid capping and edge splitting.

Direct compression is not recommended for the free acid at unit doses above 100 mg because poor compressibility and low flow lead to weight variation outside USP <905> limits. Roller compaction with ribbed rolls at a specific compaction force of 4–6 kN/cm and roll gap of 2–3 mm is a suitable dry granulation route for moisture-sensitive formulations. The compact is milled through a 0.8 mm screen, and the 18–60 mesh fraction is retained. Fines below 60 mesh are recycled to the compactor. The final blend is monitored for bulk density and tapped density by USP <616>; the target Carr index is ≤25. For tablets containing 300 mg lenacapavir free acid, the total tablet weight may approach 900–1100 mg; therefore, a tablet hardness range of 80–120 N and disintegration time of ≤15 minutes in 0.1 M HCl are typical release targets. Dissolution performance is characterized according to USP <711> using a validated method, and release limits are set from clinical batch data.

For capsule filling, the roller-compacted granules are filled on a dosator-type machine at relative humidity below 40% RH. Weight variation is monitored according to USP <905>, and content uniformity is assessed by USP <905> if the dosage unit contains less than 25 mg active substance; for 300 mg strengths, uniformity of mass is typically sufficient. The use of sodium stearyl fumarate at 0.25–0.5% w/w instead of magnesium stearate may be required if the granule surface becomes hydrophobic and slows dissolution in 0.1 M HCl. Capsule shell selection is based on moisture vapor transmission rate; hard gelatin capsules are stored below 40% RH, while hypromellose capsules may be used for low-moisture API batches.

For granule presentations, lenacapavir free acid is processed by fluid-bed top-spray granulation with a binder solution of hypromellose or povidone at 5–10% w/w. Granule size is controlled to 300–710 µm for dose uniformity and sprinkle use. The granules are dried at inlet air temperature of 45–60°C to product temperature ≤40°C. The dried granules are passed through a 0.8 mm screen and lubricated with 0.25% w/w sodium stearyl fumarate. Packaging into unit-dose sachets occurs below 40% RH; if the API is exposed above 60% RH, pre-drying at 40°C for 4 h is performed before further processing. Moisture uptake is measured by dynamic vapor sorption at 25°C/60% RH and 25°C/75% RH; a mass increase above 1.0% at 60% RH typically requires a dryer line modification.

When Sterile Aqueous Processing Requires Sodium Salt Replacement of the Free Acid

The free acid has insufficient aqueous solubility at subcutaneous injection volumes, so the sodium salt is used for injectable presentations. Injectable-grade lenacapavir sodium is dissolved in a buffered vehicle and pH-adjusted to 6.0–7.5. The solution is filtered through a sterilizing-grade 0.2 µm membrane filter and filled aseptically under EU GMP Annex 1, ISO 14644-1 class 5 conditions. Because the approved maintenance dose is 927 mg subcutaneously every 26 weeks, each single-dose container carries a high drug load; therefore, the API must meet stringent endotoxin limits by USP <85> and particulate matter limits by USP <788>. The injectable API is not terminally sterilized as a dry powder. Terminal moist heat sterilization of lenacapavir sodium may generate degradation products; the primary sterilization strategy is aseptic processing with a pre-filtration bioburden limit and sterilizing filtration of the final drug product. The API release for injection also includes bacterial endotoxin testing, bioburden by membrane filtration, and container closure integrity testing on finished vials by vacuum decay or dye ingress.

Sterile-grade lenacapavir sodium is not interchangeable with oral-grade free acid. The injectable material is released with lower bioburden, higher clarity requirements after reconstitution or dissolution, and tighter control of chloride and sodium content. Drying of the sodium salt in a vacuum dryer is controlled by Karl Fischer water ≤1.0% and residual solvent limits. The dried material is double-bagged in low-density polyethylene inside an ISO class 8 cleanroom and then transferred to the sterile manufacturing suite. The final subcutaneous injection is a solution, not a suspension or depot polymer system. Subvisible particle counts are controlled by light obscuration with limits defined in USP <788>; large-volume limit conversions are not applied because the presentation is a small-volume injectable. Needle gauge and injection volume are constrained by the solution viscosity and the 3 mL administration volume.

Formulation Stress Differences Across Established Antiretroviral API Classes

Lenacapavir differs from nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, integrase strand transfer inhibitors, and protease inhibitors in the manufacturing stress applied to the API. NRTI and INSTI tablets are often direct-compressed or wet-granulated without severe solubility constraints, whereas lenacapavir free acid requires particle engineering and moisture control to achieve adequate release. Long-acting injectable rilpivirine and cabotegravir are formulated as intramuscular suspensions that rely on milled particle size and depot dissolution; lenacapavir injection is a subcutaneous solution that relies on the sodium salt solubility and subsequent slow elimination. The API release specifications therefore emphasize different attributes: particle size and solid-state form for oral lenacapavir, and clarity, colour, pH, bioburden, and endotoxin for injectable lenacapavir. These differences affect scale-up and technology transfer because the same molecule cannot be processed identically across both routes. Tablet and capsule grades are not interchangeable with injectable grade due to bioburden and particulate controls; a separate supply chain and cleaning validation are required under 21 CFR 211.67 and ICH Q7.

Stability of lenacapavir API is evaluated under ICH Q1A(R2) conditions at 25°C/60% RH and 40°C/75% RH. The free acid is stored in double polyethylene bags inside fibre drums, with desiccant when the sodium salt is used. A retest period is assigned based on long-term data; the API should not be exposed to strong oxidizers, and any residual solvent control must include the solvent used in the final recrystallization. For oral dosage forms, dissolution testing uses USP <711> apparatus II at 50–75 rpm in 900 mL media; for injectable content, subvisible particle testing uses USP <788>. The free acid should not be exposed to RH > 60% without pre-drying, and the sodium salt should not be dry-heat sterilized. Avoid combining the free acid with amine-based additives that can form salts or cause pH microclimate changes; incompatible lubricants include magnesium stearate in excess of 1.0% w/w because of delayed dissolution. The injectable grade should not be substituted for oral grade in a tablet formula without re-qualification of bioburden and particle size. Published data for this specific configuration is limited; therefore, process ranges are confirmed by laboratory-scale design of experiments and engineering batches before full-scale manufacture.