Before sterile filtration of the deprotected boronic acid solution, the ammonium trifluoroacetate counterion is displaced by pH adjustment with sodium hydroxide or by salt exchange using aqueous sodium chloride, because residual trifluoroacetate contributes to vial headspace acidity and accelerates hydrolytic cleavage of the boronate ester. The pinanediol protecting group is removed in a preceding deprotection unit operation by transesterification or acidic hydrolysis; the resulting free boronic acid is isolated as a solid before it enters the sterile compounding stream. In a commercial-scale lyophilized injection for a boronate-containing proteasome inhibitor, the bulk compounding solution is prepared at 5±3 °C under nitrogen to maintain dissolved oxygen below 0.5 ppm. The active moiety is added at an equivalent of 3.5 mg free boronic acid per vial, with mannitol as bulking agent at 35 mg per vial, giving a fixed ratio of 1:10 active moiety to mannitol. The solution is filtered through a 0.45 μm polyethersulfone clarification membrane followed by a 0.22 μm sterilizing-grade PVDF filter; filling accuracy is maintained at ±2% on a peristaltic filling line. Lyophilization uses a shelf-freezing ramp to -40 °C over 120–180 min, primary drying at -15 °C shelf set point with chamber pressure of 80–120 mTorr for 18–24 h, and secondary drying at 25 °C for 6–8 h. Stopper seating occurs under nitrogen with residual oxygen below 2%. Terminal product types are single-dose 10 mL Type I borosilicate vials containing a white to off-white lyophilized cake, reconstituted with 3.5 mL of 0.9% sodium chloride to a final concentration of 1 mg/mL active moiety. Compliance standards include USP <1> Injections, USP <788> particulate matter, USP <85> bacterial endotoxins, 21 CFR 211.42 for aseptic processing areas, ICH Q1A(R2) for photostability and thermal cycling studies, and ISO 14644-1:2015 Class 5 for critical processing zones. Batch records document filter integrity tests, fill-volume checks, and lyophilization thermocouple data because this product class shows cake collapse when chamber pressure exceeds 150 mTorr during primary drying.

Which Dry Granulation Parameters Prevent Sticking at 1.5% w/w Drug Load?

After conversion of the pinanediol-protected salt to the free boronic acid, oral capsule filling is performed with a dry granulation intermediate rather than direct blend because the unprotected active moiety exhibits electrostatic adhesion to metal contact surfaces. The formulation uses active moiety equivalent to 2.3 mg per 150 mg fill weight, corresponding to 1.53% w/w. Microcrystalline cellulose at 65% w/w, anhydrous dibasic calcium phosphate at 20% w/w, croscarmellose sodium at 4% w/w, and magnesium stearate at 0.5% w/w are blended in a bin blender at 10 rpm for 20 min. The blend is compacted on a roller compactor with roll gap 2.0 mm, roll force 8–12 kN/cm, and granulator screen 1.0 mm; after compaction, the granule solid fraction is maintained at 0.62–0.68 because lower solid fraction increases fines and higher solid fraction reduces compactability. Capsule filling is performed on an intermittent-motion encapsulation machine, size 3 HPMC capsules, with target fill weight 150 mg and acceptance range ±5%. The terminal product type is hard hypromellose capsules in cold-form blister packaging with PVC/PCTFE foil and nitrogen flush. Compliance standards are USP <711> dissolution using 900 mL of pH 4.5 acetate buffer at 37 °C with paddle speed 50 rpm, USP <905> uniformity of dosage units, USP <1216> friability when the granulate is compressed into cores, ICH Q3C for residual solvents where the TFA counterion is confirmed below the qualified limit by ion chromatography, and ICH Q3A(R2) for degradation product thresholds. Dissolution data for this specific configuration is limited; when the method is transferred, the Q value is established according to ICH Q6A rather than assumed from a reference product.

At drug loads above 2.0% w/w, direct compression of the deprotected boronic acid is generally rejected because the crystalline active moiety has poor compactability and punch sticking risk under ambient humidity above 40% RH. Wet granulation using water is also avoided because the boronic acid group undergoes pH-dependent hydration and possible oxidation; instead, a dry granulation route is followed by tablet compression. The formulation addition ratio is active moiety 1.8% w/w, lactose monohydrate 68% w/w, microcrystalline cellulose 25% w/w, crospovidone 3.0% w/w, sodium stearyl fumarate 1.2% w/w. The granulated intermediate is compressed on a rotary tablet press with 10 kN pre-compression and 20 kN main compression; tablet hardness is targeted at 70–90 N, thickness 3.0–3.5 mm, and friability below 0.8% after 100 revolutions. Tablets are coated with an aqueous film coat at 2–3% w/w weight gain using a perforated pan coater with inlet air temperature 55–65 °C and product bed temperature 38–42 °C. The terminal product type is an immediate-release film-coated tablet, 7 mm round or 10 mm oblong, packaged in PA/Al/PVC blisters with desiccant. Compliance standards for this oral solid dose include USP <905>, USP <1216> friability, USP <711> dissolution, 21 CFR 211.166 stability, and ICH Q3D for elemental impurities where the tablet core is tested for copper and zinc residues from catalyst sources. Operational boundary: compression area relative humidity should be maintained at 20–35% RH because higher humidity increases sticking and brittle fracture of the boronic acid particles.

When Pre-Filled Syringe Presentation Becomes the Preferred Injectable Configuration

If the lyophilized vial is unacceptable for high-throughput hospital administration, a pre-filled syringe solution can be prepared from the same deprotected active moiety. The formulation ratio uses active moiety 1.0 mg/mL, sodium chloride 9.0 mg/mL, citrate buffer 10 mM at pH 5.0, and nitrogen-sparged water for injection. The compounding vessel is blanketed with nitrogen to keep dissolved oxygen below 0.5 ppm because the boronic acid is susceptible to oxidative cleavage. Sterile filtration occurs through 0.22 μm PVDF or polyethersulfone; fill volume is 1 mL or 2 mL in cyclic olefin polymer syringes with fluoroelastomer plunger stoppers. Terminal sterilization by moist heat is not feasible because the active moiety degrades above 40 °C at pH 5.0; therefore aseptic processing under ISO 14644-1:2015 Class 5 is mandatory. Compliance standards include USP <1> Injections, USP <790> visible particulates, USP <788> particulate matter, ISO 11608-1:2022 needle-based injection system compatibility, and 21 CFR 211.94 drug product containers. Leachables testing follows USP <1664> for polymeric syringe components. Terminal product type is a single-dose pre-filled syringe containing 1 mg/mL active moiety, stored at 2–8 °C and protected from light. The finished syringe is inspectable for sub-visible particles with light obscuration count thresholds at 10 μm and 25 μm per USP <788>. Operational limit: prolonged contact with silicone oil above 0.5 mg/syringe can alter surface tension and generate visible droplet artifacts; published data for this specific configuration is limited.

Granule Flow, TFA Residual, and Single-Dose Sachet Filling for Oral Reconstitution

Granulated intermediates intended for single-dose sachet reconstitution are produced by dry granulation or low-moisture wet granulation with ethanol, with the latter requiring explosion-proof processing and strict drying below 45 °C product temperature. The addition ratio for a single-dose sachet is active moiety 1.0 mg per 400 mg granule, mannitol 340 mg, citric acid 10 mg, and sodium bicarbonate 15 mg, giving a final solution pH of 4.0–4.5 after reconstitution in 20 mL water. The granulation process on a fluid-bed top-spray unit uses ethanol as binder solvent, inlet air temperature 45 °C, product temperature 28–32 °C, and spray rate 5–8 g/min for a lab-scale batch of 2 kg; after drying, residual ethanol is reduced to ≤0.5% w/w and granules are sized through a 1.0 mm screen. Sachet filling is performed on a vertical form-fill-seal machine with ±3% fill weight tolerance and nitrogen flush. Terminal product type is a granule for oral suspension in a PET/aluminum/LDPE sachet, reconstituted to 0.05 mg/mL active moiety. Compliance standards include USP <905> uniformity of dosage units, USP <711> dissolution, ICH Q3C for residual ethanol, ICH Q3D for elemental impurities, ICH Q3A(R2) for degradation products, and 21 CFR 211.166 stability. Residual trifluoroacetate in the granule is measured by ion chromatography with acceptance criterion ≤0.1% w/w; because no harmonized ICH Q3C class applies to trifluoroacetate, the limit is justified by ICH Q3A(R2) toxicological qualification.