Biological target identification and validation are among the most important steps in developing a new drug. Drug target validation involves proving that either DNA, RNA, or a protein molecule is directly involved in a disease process and can be a suitable target for development of a new therapeutic drug.

To qualify as ‘druggable’, a target must be accessible to the proposed drug molecule, and a measurable biological reaction must be provoked as a consequence of the drug interacting with the target. This reaction may be measured both in vitro and in vivo.

Once the target has been identified, for example by genomic or proteomic investigations, the target is then validated in functional studies. The main strategies involved in target validation are gene knockout studies and direct inhibition of the target by small molecules, peptides, antibodies or any other class of inhibitors. The knockout approach genetically inhibits the target, thereby mimicking the action of the drug and allows a drug to be modeled before it is developed.

Information about established drugs and drug-target interactions is available online via public databases such as Drug Bank and the Therapeutic Targets Database. In addition, information on potentially novel drug targets can be found at Center Watch's, Drugs in Clinical Trials Database, which identifies trends in drug development based on current clinical trials.

Examples of popular knockout cell lines for drug target identification and validation
ABAT ABCA1 ABCC1 ACE ACHE
ACVR2A ADA ADIPOR1 ADIPOR2 ADK
ADORA2A ADORA2B ADRA1A ALAD ANXA1
AR ASIC1 ATP2C1 BCHE BLVRB
CA2 CACNA1H CACNA2D1 CACNA2D2 CACNB1
CACNB2 CACNB3 CACNB4 CCKBR CCND1
CHD1 CHRNB2 CKB CLCN2 CNR1
COMT CPT1A CPT2 CYP51A1 DPP4
EPOR ESRRG FADS1 FASN FGF2
FN1 FTL GAA GABBR1 GABRA5
GABRB3 GANAB GANC GGCX GLRB
GSR GSS HMMR HPRT1 HTR6
IFNAR1 IFNAR2 IFNGR1 IFNGR2 IL11RA
IMPDh2 ITGA2B JUN KCNC1 KCND2
KCNh4 KCNJ11 KCNK2 KCNQ1 KCNQ2
KEAP1 KMT2C M6PR MAOA MAP1A
MAP2 MAP4 MME MMP11 MMP15
MMP16 MMP17 MMP24 MMP25 MS4A2
MTR MUT NOS2 NR3C2 PDE10A
PDE4A PDE5A PDE7A PDE8A PDXK
PGF PLAU PLAUR PNP POLE4
PRKAG1 PRKAG2 PRLR PROS1 PSMB10
PSMB8 PSMB9 PTGER3 QPRT RAMP1
RAMP2 RARG RFK RXRA RXRB
S1PR5 SCN1B SCN5A SCNN1D SHMT1
SIGMAR1 SLC18A2 SLC5A2 SMS SOAT1
SQLE SRD5A1 SYT2 THRB TOP1MT
TOP2B TPMT TSPO TUBA1A TUBA4A
TUBB1 TUBB4B TUBG1 UGCG VAMP1
VEGFA VEGFB VKORC1