INTRODUCTION:

Apremilast is chemically named as N-[2-[(1S)-1-(3-ethoxy-4-methoxyphenyl) -2-(methylsulfonyl)ethyl]-1,3-dioxo-2,3-dihydro-1H-isoindol-4-yl]acetamide. It has an empirical formula of C22H24N2O7S, and a molecular weight of 460.5 g mole−1.¹ FDA approval for this molecule was received on 21 March 2014 in the USA toward the first-line treatment of psoriatic arthritis. OtezlaVR, an oral preparation is marketed by Celgene Corporation. Apremilast tablets are manufactured and marketed in various doses—10mg, 20mg and 30mg.^2,3,4 In the year 2017, the Drug Controller General of India also approved Apremilast for marketing in India.⁵

It is soluble in many organic solvents such as acetonitrile and DMSO, but insoluble in aqueous media. It is utilized for the healing of certain types of Psoriasis and Psonatic arthritis.⁶ It may also be utilized for other immune system associated inflammatory diseases. APR is a selective inhibitor of the enzyme phosphodiesterase 4 and stops spontaneous production of TNF-alpha from human rheumatoid synovial cells is taken by mouth.^7,8 Patent EP2276483 B1 demonstrates a number of polymorphic forms of Apremilast, i.e., Forms A, B, C, D, E, F and G. Patent EP3455209A1 describes the preparation method for various crystalline (solid) forms of Apremilast i.e., Form-M, Form-N, Form-O and Form-P, Crystallineform II.^9,10 Apremilast is a phthalimide derivative. It is a white to pale yellow, non-hygroscopic powder that is practically insoluble in water and buffer solutions in a wide pH range, but is soluble in lipophilic solvents such as acetone, acetonitrile, butanone, dichloromethane, and tetrahydrofuran.¹¹

Fig 1: Structure of Apremilast

Drug profile:

Table 1 - Information about Apremilast.

Drug name	Apremilast
Chemical name	N-[2-[(1S)-1-(3ethoxy-4-methoxyphenyl)-2-methylsulfonylethyl]-1,3dioxoisoindol-4-yl] acetamide.
Chemical formula	C₂₂H₂₄N₂O₇S
Molecular weight	460.501 g/mol
Melting point	156-158℃.
Solubility	Acetonitrile and Methanol.
Half life	6 - 9 hours
Pak value	Strongest acid- 14.42 Strongest base- 8.91
log P value	log P 2.69 log P 2.74
log S value	3.1

Pharmacology:

The drug acts as a selective inhibitor of the enzyme phosphodiesterase 4 (PDE-4). PDE is a group of enzymes, which have different biological properties. PDE enzymes have Eleven different families is been identified out of that PDE-4 plays a dominant role in inflammatory diseases. PDE-4. reduces the intracellular cAMP by hydrolyzing it into AMP. This, in turn, increases the production of pro-inflammatory cytokinin like tumor necrosis factor (TNF-a) and interleukins. This also suppresses the anti-inflammatory cytokinin. It is acts as a selective antagonist of PDE-4. This results in the accumulation of cAMP intracellularly, and initiates the release of anti-inflammatory cytokines and curtails the gene expression of numerous pro-inflammatory cytokines. The intracellular elevation of cAMP also downregulates T helper cells and myeloid dendritic cells.^12,13

Phrmacokinetic:

The absolute bioavailability of apremilast following oral administration of 20 mg is 73%; food does not alter the extent of absorption.¹⁴ After the administration of multiple ascending doses in healthy adults, the area under the curve (AUC) and peak plasma concentration (C_max) increased linearly, with a median time to peak concentration (T_max) of approximately 2.5 hours. In patients with PsA, the steady-state maximum concentration (C_max) and Area under curve(AUC) values are higher by 57% and 38%, respectively. Apremilast is distributed with a volume of distribution (Vd) of 87 L. Binding to human plasma proteins is approximately 68%.¹⁵ With respect to the clearance of the drug, Hoffman et al. noted that approximately 58% and 39% of the radioactive apremilast was excreted in the urine and feces, respectively.¹⁶

A. HPLC Technique available Apremilast:

In the method development of HPLC, the major solvent system used is acetonitrile and water (pH adjusted) firstly, followed by methanol and water. Other column used, the flow rate, wavelength of detection, RT (retention time) have been summarized in the table.

Features of methods.²²

Study in bulk and pharmaceutical dosage form

Table 2 - HPLC methods in bulk and pharmaceutical

Sr. No	Drug name	System	Description	Reference
1	Apremilast	Isocratic	Stationary phase- Inertsil C8 (250 X 4.6 mm) 5µ column Mobile phase- Buffer and methanol (47:53 % v/v) Flow rate-1.5 ml/min Retention time-8.3 min Wavelength of detection-230nm	17
2	Apremilast	Isocratic	Stationary phase- C18 Column (based on99.999% ultrahigh purity silica) 250 mm ×4.6 mm, 5 μ particle size, Mobile phase- acetonitrile Flow rate-1ml/min Retention time-2.488 min Wavelength of detection-229nm	18
3	Apremilast	Isocratic	Stationary phase- Intersil ODS3 C18 column (250 mm × 4.6 mm i.d., 5 µm particle size) Mobile phase-0.1% acetic acid and acetonitrile Flow rate-0.8 ml/min Retention time-5.4min Wavelength of detection-203nm	19
4	Apremilast	Isocratic	Stationary phase- Grace C18 column (250mm x 4.6ID, 5μm) Mobile phase- Methanol: Water (80:20, v/v) Flow rate-0.8 ml/min. Retention time-4.80 min Wavelength of detection-231nm	20
5	Apremilast	gradient	Stationary phase- Cosmosil C-18 (250 mm × 4.6 mm, 5 μm) Mobile phase- Buffer-1: Acetonitrile (10:90) v/v Buffer-1-1.0 mL of Trifluoroacetic acid in 2000 mL of HPLC grade water Flow rate-1ml/min Retention time-3.10min Wavelength of detection-230nm	21

Study in biological sample

Table 3 - HPLC methods in biological sample.

Sr. No

Drug name

System

Description

Reference

Apremilast

Rat plasma

Stationary phase- Acquity BEH C18

Column (2.1mm_50 mm, )1.7

Mobile phase- Acetonitrile

Flow rate- 0.40 mL/min

Retention time- 1.27 min

Wavelength of detection-230 nm

B. UV- visible spectrophotometric method:

UV-Visible spectrophotometry is widely used method in pharmaceutical research.

Table 4 - UV spectroscopy methods for Apremilast.

Sr. No	Drug name	System	Description	Reference
1	Apremilast (Bulk and Tablet Dosage Form)	UV Spectrophotometer (Systronic-2201)	Solvent- Acetonitrile Wavelength of detection- 230 nm	24
2	Apremilast (Bulk drug)	Jasco double beam UV-visible spectrophotometer, Model: V-630	Solvent- Methanol Wavelength of detection-230nm	25
3	Apremilast (Bulk and laboratory prepared mixture).	A double beam UV 1700 Pharmaspec	Solvent- Methanol Wavelength of detection- 230 nm	26
4	Apremilast	A double beam UV visible spectrophotometer	Solvent- Water and Methanol Wavelength of detection- 230 nm	27

C. HPTLC technique available Apremilast

Table 5 - HPTLC methods for Apremilast.

Sr. No

Drug name

Description

Chamber saturation and TLC plate development time

Reference

Apremilast

Stationary phase- Aluminium TLC plate precoated with silica gel 60 F254 (10 x 10 cm)

Mobile phase- Toluene: Ethyl Acetate (4:6v/v)

Detection - 236nm (Densitometry scanning)

CSt: 25min

PDt: 8min

Rf value: 0.64 ± 0.05

Apremilast

(Bulk and inhouse tablet)

Stationary phase- Aluminium backed precoated silica gel 60-F254 (20 x 10 cm)

Mobile phase-Toluene: Methanol (8:2 v/v)

Detection -230nm (Densitometry scanning)

CSt: 15min

PDt: 10min

Rf value: 0.55±0.02.

D. ultra pressure liquid chromatography (UPLC):

UPLC are very useful for estimation of drug in biological sample. Bioanalysis is a process used to estimate concentrations in biological samples like blood, plasma, serum, CSF and urine, also saliva for their metabolites or endogenic substances.^30-31 The process by which routine sample analysis can be classify into:

1 Reference standard preparation,

2 Development of bioanalytical method and assay procedure

3 For routine drug analysis. Application of validated bioanalytical method and acceptance conditions for analytical run and batch.³²

Table 6 - UPLC methods for Apremilast.

Sr. No

Drug name

Method

Description

Reference

Apremilast

(Rat plasma)

UPLC/MS-MS

Stationary phase-

Acquity BEHTM C18 column (100 × 2.1 mm, 1.7 μm)

Mobile phase-

Acetonitrile: ammonia (85:15)

Retation time-0.81 min

E. LC-MS method available Apremilast:

LC-MS/MS is one of the hyphenated techniques. Apremilast for which they carried out using LC-MS method by plasma, urine and fecal samples were collected. Sample preparation was done using transparent potassium bromide pellets. Spectra were recorded in wave number of 4000–400 cm_1 range.³⁴

Table 7 - LC-MS methods for Apremilast.

Sr. No.	HPLC system	Mass spectrometer	Ionization mode Conditions	Ref.
1	Shimadzu LC-10ADVP (Shimadzu Corp., Columbia, MD)	Finnigan LCQ mass spectrometer (Thermo Scientific, Waltham, MA)	Positive ionization mode	35
2	Waters 2695 Alliance Separation Module (Waters Corp., Milford, MA)	SCIEX Q Trap Applied Biosystems, Foster City, CA	Positive or negative ionization mode	36
3	Agilent 1100 HPLC system (Agilent Technologies, USA)	API4000 mass spectrometer (AB Sciex, USA)	Positive ionization mode	37

CONCLUSION:

Apremilast is approved in 2014 by USFDA. It is belongs to class 4 according to BCS class. Due to its promising results and Safety profile, Apremilast has been studied for various skin Conditions and indications. The molecule is not yet included in any of the techno-legal Books. Hence the analysis of this molecule becomes tricky and Intricate. Analysis of the drug plays a significant role during formulation to identify the drug and its metabolites

The present review illustrates various analytical approaches exercised for the evaluation of Apremilast. A numerous Investigation had perform including, HPLC, UV spectroscopy, HPTLC, UPLC and LC-MS in bulk, Pharmaceuticals dosage form and biological sample. Mostly LC-MS and HPLC methods have been used for selective and sensitive estimation.

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Received on 12.01.2021 Modified on 24.01.2021

Research Journal of Science and Technology. 2021; 13(2):142-146.

DOI: 10.52711/2349-2988.2021.00021