Table 1.

Polymorphisms and genomic variants underlying responses to anti-PD drugs.

Drugs	Gene	SNP	Effect	References
L-DOPA	COMT gene	rs4680	Higher frequency of COMT LL genotype in patients requiring lower L-dopa dosage	[21, 22, 78]
			No association between COMT polymorphism and the occurrence of LID	[22, 33]
			Higher frequency of COMT LL genotype in patients with dyskinesia	[23, 32]
			Higher frequency of COMT LL/LH genotypes in patients with higher Epworth sleepiness scale scores	[79]
		rs165815	Higher frequency of COMT C allele in patients with visual hallucinations	[54]
	DAT gene	rs28363170 & rs393795	Lower frequency of the combination of the two genotypes of the DAT gene in patients with LID	[80]
		rs28363170	Higher frequency of DAT gene VATR sequence in patients with LID	[27]
			Higher frequency of DAT gene VATR sequence in patients with Levodopa-induced hallucinations and psychosis	[27]
			Lower frequency of DAT1 9/9 genotype in patients with LID	[28]
		rs393795	Higher frequency of DAT C genotype in patients with later occurrence time of LID	[27]
	DRD2 gene	rs1800497	DRD2/ANKK1 is significantly associated with increased doses of L-dopa	[28]
			No association between TaqIA polymorphism and the motor fluctuation	[28]
			Lower frequency of DRD2 13 or 14 alleles in patients with peak-dose dyskinesias	[34, 35]
			Higher frequency of DRD2 14/15 genotype in patients with LID	[36]
			Higher frequency of DRD2 C allele in patients with delayed visual hallucinations	[56]
	DRD3 gene	rs6280	Higher frequency of DRD3 C genotype in patients with visual hallucinations	[55]
	MAO-A gene	rs6323	No association between MAO-A and the occurrence of LID	[22]
		rs1799836	Higher frequency of A allele and AA genotype in patients LID	[23]
	BDNF gene	rs6265	No association between BDNF and the occurrence of LID	[22]
			Higher frequency of BDNF met allele in patients LID	[81]
	HOMER1 gene	rs4704560	Lower frequency of HOMER1 G allele in patients with LID	[46]
	ACE gene	rs4646994	Higher frequency of ins/ins genotype in patients with L-DOPA-induced psychosis	[82]
	SLC22A1 gene	rs622342	Higher frequency of the minor C allele in patients requiring higher anti-Parkinsonian drugs dosage	[29]
	SV2C gene	rs30196	Higher frequency of the C allele in patients requiring lower L-dopa dosage	[30]
	SLC6A3 gene	rs2836371	Higher frequency of SLC6A3 9R allele in patients requiring lower L-dopa dosage	[30]
	MTHFR gene	rs1801133	Higher frequency of MTHFR TT677 mutants in patients with lower daily levodopa dose	[83]
			Higher frequency of C677T in patients with L-dopa-induced hyperhomocysteinemi	[53]
			Lower frequency of C677T TT homozygosity in patients with L-DOPA resistance	[53]
	EIF4EBP2 gene	rs1043098	Higher frequency of CC homozygous in patients with the later occurrence of LID and LID peak	[84]
Dopamine Receptor Agonists	DRD2 gene	rs1800497	No association between Taq1 genotypes and the reaction of pramipexole	[63]
			Higher frequency of Allele A2 in patients with the sudden onset of sleep in patients taking bromocriptine, pergolide, or cabergoline	[85]
	DRD3 gene	rs6280	Higher frequency of Ser/ser genotype in patients with a higher response rate of pramipexole	[60]
	DRD4 gene	DRD4 48-bp VNTR	No association between the Taq1 genotype and the reaction of pramipexole	[63]
COMT inhibitors	COMT gene	rs4680	COMT HH genotype prolongs the ON time of patients treated with entacapone	[71]
			COMT gene rs4608 polymorphism modifies the motor response to COMT inhibitors entacapone	[86]
	UGT1A6 gene	A528G SNP	Higher frequency of A528G SNP with a higher risk of hepatotoxicity induced by entacapone and tolcapone	[72]
MAO Inhibitors	DRD2 gene	rs2283265 & rs1076560	The two genotypes can significantly improve the motor function of patients treated with rasagiline	[68]

Abbreviations: L-dopa: levodopa; COMT: catechol-O-methyltransferase; LID: levodopa-induced dyskinesia; DR: dopamine receptor; MAO: monoamine oxidase; DAT: dopamine transporter.