N-[2-(Diethylamino)Ethyl]-5-[(Z)-(5-Fluoro-2-Oxo-1,2-Dihydro-3H-Indol-3-Ylidene)Methyl]-2,4-Dimethyl-1H-Pyrrole-3-Carboxamide (2Z)-But-2-Enedioate

N-[2-(Diethylamino)Ethyl]-5-[(Z)-(5-Fluoro-2-Oxo-1,2-Dihydro-3H-Indol-3-Ylidene)Methyl]-2,4-Dimethyl-1H-Pyrrole-3-Carboxamide (2Z)-But-2-Enedioate, a multi-targeted receptor tyrosine kinase inhibitor exhibiting pH-dependent aqueous solubility typical of a BCS Class II weak base, is pre-blended with a 75:25 mixture of spray-dried mannitol (Ph.Eur. 10th Ed.) and silicified microcrystalline cellulose in a diffusion blender equipped with an intensifier bar. The geometric dilution sequence introduces the maleate salt at a final tablet-core weight percentage of 20.0% w/w—corresponding to a 25 mg label claim within a 125 mg target fill weight—followed by a 3-minute main blend after addition of 2.0% w/w crospovidone (Type A, particle size D50 110 µm) and 0.75% w/w magnesium stearate (vegetable-source, specific surface area 5.8 m²/g) passed through a 600 µm mesh. Blend uniformity is assessed in accordance with USP <905> Uniformity of Dosage Units, with stratified sampling across 10 locations and an acceptance value (AV) limit of ≤15.0; content uniformity of the film-coated finished product is additionally verified by HPLC against USP Sunitinib Malate RS at a retention time of 6.8 min on a C18 column (150 × 4.6 mm, 3.5 µm) employing a mobile phase of 0.05 M potassium phosphate buffer (pH 3.2) and acetonitrile (65:35 v/v). Compression runs on a 27-station rotary press (B-tooling, 8 mm round concave punches) are executed at a turret speed of 45 rpm, with pre-compression force maintained at 4 kN and main compression force oscillating between 12 kN and 16 kN to achieve a tablet hardness of 7–9 kp and friability below 0.3% after 100 revolutions (USP <1216>). The resulting core tablets are coated in a 24-inch perforated pan system using an aqueous film coat consisting of partially hydrolyzed polyvinyl alcohol, titanium dioxide, talc, and iron oxide pigment to a weight gain of 3.5% w/w, with inlet air temperature controlled at 65 °C and bed temperature monitored at 42 °C. Process validation acceptance criteria follow FDA 21 CFR 211.110 sampling requirements and ICH Q7 Good Manufacturing Practice Guidance for Active Pharmaceutical Ingredients. The terminal pharmaceutical form is a light-orange immediate-release film-coated tablet containing Sunitinib maleate equivalent to 25 mg sunitinib.

Under What Circumstances Does Wet Granulation Outperform Direct Compression for High-Dose Sunitinib Maleate Formulations?

A transition to high-shear wet granulation is warranted when the maleate salt dose exceeds 50 mg per unit and the bulk API exhibits a Carr’s Compressibility Index above 30% or an angle of repose greater than 45°, conditions that lead to unacceptable weight variation on high-speed presses. The process charges a 600 L high-shear mixer with an intragranular phase comprising the maleate salt at 16.7% w/w of the final core weight (50 mg API in 300 mg target mass), lactose monohydrate (200 mesh), and a binder of pre-gelatinized starch (5.0% w/w). Water purified by reverse osmosis (USP <645> conductivity ≤ 1.3 µS/cm) is sprayed at a rate of 2.5 kg/min under an impeller speed of 150 rpm and chopper speed of 1800 rpm until the power consumption plateau indicates granule formation; wet mass is subsequently discharged through a 4 mm mesh and dried in a fluid-bed dryer with an inlet temperature of 75 °C until a loss-on-drying endpoint of 1.8–2.2% (USP <731>) is achieved. Extragranular croscarmellose sodium (3.0% w/w) and magnesium stearate (1.0% w/w) are blended in a 500 L bin tumbler for 2.5 minutes at 8 rpm. Compression is performed on a 45-station press with oval tooling (11 × 6 mm, fully tooled), target hardness 12–15 kp, and disintegration time below 5 minutes in 0.1 N HCl at 37 °C (USP <701>). All stages are executed under a relative humidity of ≤30% RH because the amorphous content of the granulated material accelerates moisture sorption and hydrolysis of the maleate counterion. Regulatory filing incorporates ICH Q1A(R2) long-term (25 °C/60% RH, 36 months) and intermediate (30 °C/65% RH, 12 months) stability protocols, alongside photo-stability testing (Q1B, Option 2, 1.2 million lux-h visible and 200 W-h/m² UV). The finished product is a bottle-packaged immediate-release film-coated tablet embossed with identification code, supplied with desiccant canisters.

A feedstock solution of the maleate salt and hypromellose acetate succinate (HPMCAS-MF, acetyl content 7.0–9.0%, succinoyl content 10.0–14.0%) at a 30:70 w/w drug-to-polymer ratio is prepared in a 70:30 v/v dichloromethane:methanol binary solvent system with a total solids loading of 5.5% w/w. The solution is atomised through a two-fluid nozzle into a Niro PSD-1 closed-cycle spray dryer operated with an inlet gas temperature of 85 °C, outlet temperature maintained at 43–46 °C, and atomisation pressure of 1.8 bar using nitrogen conforming to ISO 8573-1:2010 Class 1.4.1 for particle and oil content. The spray-dried dispersion (SDD) is collected in a cyclone and subjected to secondary vacuum drying at 40 °C for 24 h to achieve residual solvent levels below 600 ppm for dichloromethane and 3000 ppm for methanol, meeting ICH Q3C(R8) Class 2 and Class 2 limits respectively. Solid-state characterisation by modulated differential scanning calorimetry (ASTM E2550-21) verifies the absence of crystalline endotherms, and X-ray powder diffraction (XRPD) scans over a 2θ range of 3–40° at 0.02° step size confirm an amorphous halo. The downstream processing blends the SDD with extragranular microcrystalline cellulose (Avicel PH-102), croscarmellose sodium (2.0% w/w), and colloidal silicon dioxide (0.5% w/w) for direct compression, achieving a tablet tensile strength above 1.8 MPa at a solid fraction of 0.85. Dissolution testing in 900 mL of 0.1 N HCl containing 2.0% sodium dodecyl sulfate (USP Apparatus 2, 75 rpm) demonstrates >85% release within 30 min, a marked improvement over uncompounded maleate salt that yields <30% release under identical conditions. Compliance with FDA SUPAC-MR guidance for non-compositionally proportional changes is supported by f2 similarity factor analysis with a pre-defined acceptance value of ≥50. The terminal product is an immediate-release tablet incorporating an amorphous solid dispersion of Sunitinib maleate.

Hot-Melt Extrusion with Vinylpyrrolidone-Vinyl Acetate Copolymer: Processing Parameters and Physical Stability of the Amorphous State

A co-rotating twin-screw extruder with a barrel length-to-diameter ratio of 40:1 (Leistritz ZSE 18 mm) is configured with 10 barrel zones and vacuum venting at zone 8. The maleate salt is pre-mixed at 25% w/w with copovidone (Kollidon VA 64, glass transition temperature Tg 107 °C) and fed gravimetrically at 1.2 kg/h into the feed throat. Barrel zone temperatures are profiled from 120 °C (zone 2) to 175 °C (zone 7), with a die temperature of 165 °C; screw speed is fixed at 150 rpm, generating a specific mechanical energy input of approximately 0.25 kWh/kg. Melt pressure recorded at the die does not exceed 35 bar, and melt viscosity measured inline via slit rheometer remains below 1200 Pa·s at a shear rate of 100 s⁻¹. The extruded strand is air-cooled on a conveyor belt and pelletised to granules with particle size D50 of 650 µm. Residual crystallinity is examined by hot-stage polarised light microscopy and by measurement of the enthalpy recovery peak at Tg using DSC with a heating rate of 20 °C/min; an enthalpy relaxation below 1.5 J/g is considered acceptable. The milled extrudate is filled into size 1 hard gelatin capsules using an intermittent-motion dosator machine at 50,000 capsules/h, with fill weight controlled at 200 mg ± 5% to deliver 50 mg of the maleate salt per capsule. Disintegration testing (USP <2040>) yields <10 min in water, and dissolution in 0.1 N HCl with 0.5% SLS shows a mean dissolved percentage of 92% at 45 min. Risk assessment per ICH Q9 identifies barrel residence time exceeding 5 min as a critical quality attribute because the maleate salt undergoes progressive decarboxylation above 180 °C, reinforcing the necessity of maintaining zone 7 below this threshold. The terminal dosage form is an immediate-release hard gelatin capsule containing a copovidone-based amorphous solid dispersion of Sunitinib maleate, intended for bioequivalence studies submitted under FDA 21 CFR 314 and EMA Guideline on the Investigation of Bioequivalence.

Containment strategies for the maleate salt, which exhibits an occupational exposure limit (OEL) of 0.1 µg/m³ and is classified as a cytotoxic compound under OSHA HCS 29 CFR 1910.1200, are central to a dedicated isolator-based API finishing train. The crystallisation step is executed in a 100 L glass-lined Hastelloy reactor within an ISO 14644-1 Class 5 rigid-wall isolator maintained at negative pressure (−60 Pa relative to the surrounding room). Recrystallised crude maleate salt is dissolved in a 1:8 w/v ratio of purified N,N-dimethylacetamide (water content ≤ 0.05%) at 75 °C and solvent-to-antisolvent precipitation is effected by controlled addition of filtered acetone (ratio 1:5) over 90 min using a syringe pump, generating a crystalline form with a median particle size of 18 µm. The slurry is discharged through a bottom valve into an agitated Nutsche filter-dryer (0.2 m² polypropylene filter cloth, pore size 10 µm) for sequential washing with chilled acetone (2 × 10 L) and vacuum drying at 45 °C jacket temperature with intermittent nitrogen blowdowns until acetone headspace is below 500 ppm (ICH Q3C). Micronisation is performed in an isolator-integrated spiral jet mill fed at a rate of 2.5 kg/h with a grinding pressure of 5 bar and injector pressure of 6 bar, targeting a D90 of <10 µm measured by laser diffraction (ISO 13320:2020). Particle size distribution is verified by on-line laser diffraction, and environmental monitoring for airborne cytotoxic particulates follows ISO 14698-1 protocols with settle-plate and volumetric air-sampling at critical locations every 4 h during a campaign. The large-scale manufacturing campaign produces sterile, micronised Sunitinib maleate suitable as input material for ophthalmic suspension formulations or nanoparticulate drug delivery systems, with all batches released under EU GMP Annex 13 for Investigational Medicinal Products.

Stability-Indicating RP-HPLC Method for Forced Degradation Profiling and Impurity Tracking

A stability-indicating analytical procedure is validated under ICH Q2(R1) guidelines and USP <1225> for the quantification of the maleate salt and its specified degradation products. The method employs a 250 × 4.6 mm octadecylsilyl column (5 µm particle size, pore diameter 100 Å) thermostatted at 35 °C; mobile phase A consists of 0.1% trifluoroacetic acid in water and mobile phase B is 0.1% trifluoroacetic acid in acetonitrile, with a gradient programme from 25% B to 70% B over 40 min at a flow rate of 1.0 mL/min. Sample preparation dilutes the maleate salt to a concentration of 0.1 mg/mL in diluent (50:50 water:acetonitrile), which corresponds to a 10 µg on-column loading for a 10 µL injection volume. Forced degradation is conducted on aliquots: acid hydrolysis (1 N HCl, 60 °C, 2 h), base hydrolysis (0.1 N NaOH, 25 °C, 30 min), oxidation (3% H₂O₂, 25 °C, 6 h), thermal stress (105 °C, 72 h), and photolytic exposure (ICH Q1B Option 2). Peak purity is verified using a photodiode array detector with a scan range 200–400 nm and a resolution of 1.2 nm; the spectral purity threshold is set at 990. System suitability criteria include a tailing factor ≤ 2.0, theoretical plates > 10,000, and relative standard deviation of peak area ≤ 1.0% for six replicate injections. Quantification limits for the cis-isomer impurity and the 5-fluoro-oxindole derivative are 0.02% w/w (LOQ), with linearity established from LOQ to 150% of the specification limit (0.15% w/w). The validated procedure is deployed as part of a release and shelf-life testing strategy for Sunitinib maleate drug substance and drug product single-stability reference materials, and qualifies a Certified Reference Standard assigned a purity of 99.82% by mass balance (accounting for water by Karl Fischer USP <921>, residual solvents by headspace GC, and inorganic impurities by USP <233>).

For bioequivalence and first-to-file generic development, the maleate salt is filled into size 3 hard gelatin capsules using a continuous-motion dosator capsule machine operating at 75,000 capsules/h. The pre-mix combines the API at a weight percentage of 12.5% w/w (corresponding to a 12.5 mg dose per 100 mg fill weight) with a free-flowing powder blend of lactose monohydrate (310 mesh), pre-gelatinized starch (4.0% w/w filler), and colloidal silicon dioxide (0.4% w/w). Blend uniformity is monitored by NIR spectroscopy (ASTM E1655-17) with a scan count of 32 per sample and a spectral range of 1100–1800 nm, cross-validated against HPLC. Acceptable deviation of blend assay is set at 90.0–110.0% of label claim with RSD ≤ 5.0% for 10 sampling points. Capsules are sealed via a banding process (gelatin-based banding solution, drying at 25 °C for 4 h) to prevent tampering and leakage. Dissolution is conducted in 0.1 N HCl with 1.0% sodium lauryl sulfate using USP Apparatus 1 at 100 rpm; the Q-value is 80% at 60 min. The clinical trial packaging line operates under FDA 21 CFR 312 and EU Clinical Trials Directive 2001/20/EC, with double-blind labelling and randomisation codes generated by an interactive web response system. The terminal product is a blinded, hard gelatin capsule containing Sunitinib maleate 12.5 mg, supplied in HDPE bottles with child-resistant closures for multi-center oncology studies.

Lyophilisation Cycle Design When the Maleate Salt Is Required as a Parenteral Grade Powder for Pre-Clinical Intravenous Infusion

A bulk sterile formulation for reconstitution is prepared by dissolving the maleate salt at a concentration of 10.0 mg/mL in a vehicle containing mannitol at 50.0 mg/mL and ammonium acetate buffer (10 mM, pH 4.0) to enhance solubility and prevent oxidative degradation of the pyrrole ring. The solution is sterile-filtered through a 0.22 µm Polyvinylidene fluoride (PVDF) membrane and filled aseptically into 10 mL Type I glass vials with a fill volume of 5.0 mL per vial, then partially stoppered with bromobutyl rubber closures under Grade A laminar airflow. The lyophilisation cycle employs a freeze-dryer with a shelf area of 2.5 m² and ice condenser capacity of 30 kg. Freezing is conducted at a shelf-ramping rate of 1.0 °C/min to −45 °C and held for 3 h, followed by an annealing step at −15 °C for 4 h to encourage mannitol crystallisation without breakage of the cake structure. Primary drying proceeds at a chamber pressure of 150 mTorr with a shelf temperature of −25 °C for 36 h; the endpoint is determined by a Pirani/capacitance manometer differential of ≤10 mTorr and confirmed by a rise-of-vapor pressure test. Secondary drying ramps the shelf temperature to 35 °C at 0.5 °C/min and maintains it for 8 h under a pressure of 50 mTorr, yielding a residual moisture content of 1.5–2.5% w/w (coulometric Karl Fischer). Reconstitution time with 5.0 mL of Water for Injection is required to be <2 min, producing a clear solution with a pH of 4.0–4.5. The validated cycle is filed as part of the Chemistry, Manufacturing, and Controls (CMC) section of an Investigational New Drug application, referencing FDA Guidance for Industry Q1A(R2) and sterility assurance per USP <71>. The terminal dosage form is a sterile lyophilised cake containing Sunitinib maleate equivalent to 50 mg sunitinib per vial, designated for intravenous infusion after reconstitution in 0.9% sodium chloride.

Pilot-plant campaigns for reactive extraction of process-related oxindole impurities deploy a centrifugal partition chromatographic (CPC) step where the crude maleate salt is dissolved in a biphasic solvent system comprising n-heptane, ethyl acetate, methanol, and water in a volumetric ratio of 2:5:5:2. The lower phase is used as the stationary phase and the upper phase as the mobile phase, with the maleate salt loading set at 2.5 g per 100 mL of stationary phase. The CPC column (250 mL total volume, 1000 rpm rotation, 20 °C) is operated in descending mode at a flow rate of 3.0 mL/min, achieving baseline resolution between the principal API peak and the 5-fluoro-oxindole degradant at a R_s > 2.0. Collected heart-cut fractions are combined and solvent is removed by rotary evaporation at 40 °C bath temperature under 200 mbar until a heavy oil is obtained, which is then triturated with methyl tert-butyl ether (3 × 50 mL) to yield a free-flowing crystalline solid. Final purity by the validated HPLC method exceeds 99.8% area-normalised, with single impurity levels below 0.10%. This purification sequence is executed in accordance with ICH Q7 Section 12 (Validation of Purification Procedures) and is described in a Type II Drug Master File filed with the US FDA. The isolated material becomes an in-house primary reference standard of Sunitinib maleate used to qualify working standards for API release and stability testing.