Water-soluble derivatives of lipophilic drugs

Abstract

A water-soluble reference standard is useful for immunoassays of a lipophilic drugs. The reference standard is a compound of formula (I): G-(L) n -Y  (I); where G is a lipophilic drug, L is a linker which is an alkyl group or heteroalkyl group containing from 1 to 20 carbon atoms, n is 0 or 1, and Y is a water-solubilizing group such as —SO 3 − , —NR—SO 3 − , —P(═O)(OH)(O − ), or —O—P(═O)(OH)(O − ), where R is H or an alkyl group of 1 to 10 carbon atoms.

1 . A water-soluble reference standard for an immunoassay of a lipophilic drug, the standard having the formula G-(L) n -Y wherein 
 G is the lipophilic drug,    L is an alkyl or heteroalkyl linker containing from 1 to 20 carbon atoms,    n is 0 or 1, and    Y is a water-solubilizing group selected from the group consisting of —SO 3   − , —NR—SO 3   − , —P(═O)(OH)(O − ), and —P(═O)(OH)(O − ), wherein R is H or an alkyl group containing from 1 to 10 carbon atoms.    
   
   
       2 . The water-soluble reference standard of  claim 1 , wherein the lipophilic drug is selected from the group consisting of benzodiazepines, cannabinoids, opiates, cocaine, propoxyphine, phencyclidines, methaqualone, barbiturates, LSD, amphetamines, tricyclic antidepressants, and methadone.  
   
   
       3 . The water-soluble reference standard of  claim 1 , wherein Y is —NR—SO 3   − .  
   
   
       4 . The water-soluble reference standard of  claim 1 , wherein G-(L) n -Y is a compound of the formula  
     
       
         
         
             
             
         
       
     
   
   
       5 . The water-soluble reference standard of  claim 4 , wherein n is 0 and Y is —NH—SO 3   − .  
   
   
       6 . The water-soluble reference standard of  claim 4 , wherein n is 1, L is —CH 2 —, and Y is —NH—SO 3   − .  
   
   
       7 . The water-soluble reference standard of  claim 1 , wherein G is a benzodiazepine.  
   
   
       8 . The water-soluble reference standard of  claim 1 , wherein the reference standard has a solubility of at least 500 micrograms per milliliter in water at 25° C.  
   
   
       9 . The water-soluble reference standard of  claim 1 , wherein the reference standard has a solubility of at least 1 milligram per milliliter in water at 25° C.  
   
   
       10 . The water-soluble reference standard of  claim 1 , wherein the reference standard has an octanol/water partition coefficient which is constant within a pH of 2 to 14.  
   
   
       11 . The water-soluble reference standard of  claim 1 , wherein the reference standard has an octanol/water partition coefficient which is constant within a pH of 3 to 12.  
   
   
       12 . The water-soluble reference standard of  claim 1 , wherein the reference standard has an octanol/water partition coefficient which is constant within a pH of 5 to 9.  
   
   
       13 . The water-soluble reference standard of  claim 1 , wherein the reference standard, when dissolved in an aqueous mixture at an initial concentration, retains at least 50% of the initial concentration at a temperature of 45° C. for 14 days.  
   
   
       14 . The water-soluble reference standard of  claim 1 , wherein the reference standard, when dissolved in an aqueous mixture at an initial concentration, retains at least 75% of the initial concentration at a temperature of 45° C. for 14 days.  
   
   
       15 . The water-soluble reference standard of  claim 1 , wherein the reference standard, when dissolved in an aqueous mixture at an initial concentration, retains at least 90% of the initial concentration at a temperature of 45° C. for 14 days.  
   
   
       16 . The water-soluble reference standard of  claim 1 , wherein the reference standard, when dissolved in an aqueous mixture at an initial concentration, retains at least 93% of the initial concentration at a temperature of 45° C. for 14 days.  
   
   
       17 . The water-soluble reference standard of  claim 1 , wherein the reference standard, when dissolved at an initial concentration in an aqueous mixture having a pH from 2 to 13, retains at least 50% of the initial concentration at a temperature of 45° C. for 14 days.  
   
   
       18 . The water-soluble reference standard of  claim 1 , wherein the reference standard, when dissolved at an initial concentration in an aqueous mixture having a pH from 5 to 9, retains at least 50% of the initial concentration at a temperature of 45° C. for 14 days.  
   
   
       19 . The water-soluble reference standard of  claim 1 , wherein the reference standard, when dissolved at an initial concentration in an aqueous mixture having a pH from 6 to 8, retains at least 50% of the initial concentration at a temperature of 45° C. for 14 days.  
   
   
       20 . A water-soluble reference standard for an immunoassay of tetrahydrocannabinol (THC), the standard having the formula  
     
       
         
         
             
             
         
       
       wherein L is an alkyl or heteroalkyl group containing 1 to 20 carbon atoms,  
       n is 0 or 1, and  
       Y is selected from the group consisting of —SO 3   − , —NR′—SO 3   − , —P(═O)(OH)(O − ), and —O—P(═O)(OH)(O − ), wherein R′ is H or an alkyl group comprising 1 to 10 carbon atoms, and  
       wherein the compound has a solubility of at least 100 micrograms per milliliter in water at 25° C.  
     
   
   
       21 . The water-soluble reference standard of  claim 21 , wherein n is 0 and Y is —NH—SO 3   − .  
   
   
       22 . The water-soluble reference standard of  claim 21 , wherein n is 1, L is —CH 2 —, and Y is —NH—SO 3   − .  
   
   
       23 . A method of forming a water-soluble reference standard for immunoassay of a lipophilic drug, comprising: 
 functionalizing a lipophilic drug with a water-solubilizing group selected from the group consisting of —SO 3   − , —NR′—SO 3   − , —P(═O)(OH)(O − ), and —O—P(═O)(OH)(O − ).    
   
   
       24 . The method of  claim 23 , further comprising modifying the lipophilic drug with a linking group.  
   
   
       25 . The method of  claim 23 , wherein the functionalizing step comprises treating the lipophilic drug with chlorosulfonic acid.  
   
   
       26 . The method of  claim 23 , wherein the functionalizing step comprises treating the lipophilic drug with sulfuric acid.  
   
   
       27 . A method of forming a water soluble reference standard for an immunoassay of THC, comprising: 
 reacting THC-8-carboxylic acid with diphenyl phosphorous azide (DPPA) and sodium hydroxide to form THC-8-amine, and    treating the THC-8-amine with chlorosulfonic acid.    
   
   
       28 . A method of forming a water soluble reference standard for an immunoassay of THC, comprising: 
 treating THC-8-carboxylic acid with dicyclohexylcarbodiimide (DCC) and N-hydroxysuccinimde (NHS) to form an ester,    treating the ester with ammonium hydroxide to form THC-8-amide,    reducing the THC-8-amide with lithium aluminum hydride to form THC-8-amine, and    reacting the THC-8-amine with chlorosulfonic acid.    
   
   
       29 . A method of forming a water soluble reference standard for an immunoassay of benzodiazepines, comprising: 
 treating didesethylflurazepam with chlorosulfonic acid.    
   
   
       30 . An assay method for determining the presence or amount of a lipophilic drug in a sample comprising: 
 performing a first reaction by combining a sample suspected of containing a lipophilic drug with an antibody specific for the drug and a label whereby a detectable signal is produced upon binding of the antibody to the drug,    performing a second reaction by combining a known amount of a reference standard according to  claim 1  with an antibody specific for the lipophilic drug and a label whereby a detectable signal is produced upon binding of the antibody to the reference standard,    comparing the signal produced in the first reaction with the signal produced in the second reaction as a measure of the presence or amount of the drug in the sample.    
   
   
       31 . A reference standard kit comprising the reference standard of  claim 1.