WO2001040761A1

WO2001040761A1 - Inert carriers

Info

Publication number: WO2001040761A1
Application number: PCT/GB2000/004531
Authority: WO
Inventors: Anthony Corless
Original assignee: Astrazeneca Ab; Astrazeneca Uk Limited
Priority date: 1999-12-02
Filing date: 2000-11-28
Publication date: 2001-06-07
Also published as: AU1715801A; GB9928368D0; EP1242801A1; JP2003515609A

Abstract

The invention relates to adsorbing chemical samples onto metallic carrier materials for long term storage of compounds in, for example, a proprietary compound collection.

Description

INERT CARRIERS

Large collections of chemical compounds are valuable assets of research organisations. Compound collections are used in the search for agents with novel pharmaceutical, agrochemical or other fine chemical applications and are a valuable source of structural and chemical diversity used in identifying new leads as potential inhibitors of a biological target. Compound collections may contain more than 100,000 different compounds and due to increasingly efficient compound acquisition, either through commercial sources, or by high throughput synthesis, compound collections with more than 1 million different compounds are now of a typical size in some research organisations.

The handling of samples within large compound collections for the purposes of storage, retrieval and testing presents numerous problems. In most organisations samples are obtained and stored as crystalline or amorphous powders and can be dispensed relatively easily by weighing, although this often needs to be done manually because of the varying nature of the solids. Some samples are made or obtained as glassy solids, syrups, oils or liquids and are subsequently stored in these forms. The weighing of these samples is often very time consuming and wasteful.

High throughput multiple parallel synthesis (HTMPS) can generate very large numbers of individual compounds, typically 100-5000 per week, but the sample size is usually small, <100mg. To try and obtain all or most of these samples as crystalline or amorphous powders using the methods normally available to chemists would increase the overall synthesis time to such an extent that the HTMPS process would be impractical. To avoid this problem, compounds from HTMPS are stored sometimes as dry films or as solutions, usually in dimethyl sulphoxide (DMSO). The dispensing of compounds stored as dry films is often very difficult, and the difficulty increases significantly as the sample size decreases. Compounds stored as solutions can be dispensed quickly and accurately, but the manipulation and storage of the solutions subsequent to, and after, dispensing can be very problematical especially in compound handling systems designed to handle solids. In addition, some samples are unstable in solution and decompose on prolonged storage, even at low temperatures.

Increasingly the demands of a compound collection are changing. With the advent of high throughput screening (HTS) a whole compound collection of , for example, 100,000 compounds may be screened in a number of days against a new biological target, using automated or semi-automated procedures. Faced with the need for more rapid dispensing of compounds from the compound collection, the small sample size needed and the large numbers of different sample types existing in a compound collection, current systems of storage and dispensing are increasingly incompatible with modern needs. For example, a typical sample size of compound sample needed to be dispensed for HTS may be less than 0.1 mg, but despite weight variations of ±10% being tolerated for the purposes of screening, including HTS, it is not practicable to rapidly dispense such small sample sizes.

US5519 218 describes sample holders, which are cheap and disposable, for compounds in IR spectroscopy. The sample holders are made from a wire mesh and retain compound in the openings formed by the mesh to allow the IR beam to pass through said compound. The patent does not describe the retrieval of compounds from the mesh and, indeed, disposal of both the holder and compound is preferred due to low cost of the compound holder compared with traditional mineral sample holders for IR spectroscopy, such as KBr plates.

We have found that it is possible to store and retrieve compounds, even after an extended period of storage, by adsorbing the compound onto a carrier. We have found that where the carrier has a metal surface then compounds may be adsorbed onto the metal surface and retrieved, even after an extended period of storage, to recover a significant amount of the compound. A wide variety of compound types may be stored in such a system and therefore the system of storage and retrieval is particularly suited to the pharmaceutical or agrochemical industry where large numbers of compounds of varying physical properties are stored ready for screening against new biological targets.

We present as a first feature of the invention a method for storing and dispensing a compound, which comprises (1) adsorbing the compound onto a carrier having a metal surface (2)when later required removing the compound from the carrier by contacting liquid, in which the compound is soluble, with the surface of the compound containing carrier and (3) removing the liquid from the carrier.

Ideally adsorption is achieved from a solution of the compound which is brought into contact with the surface of the carrier and then removing the solvent, for example by evaporation. Extraction of the compound from the carrier may be achieved by contacting the carrier with the compound adsorbed on it with a liquid which is a suitable solvent for the compound , and then removing the carrier from the liquid. The liquid may be separated from the carrier by passing the liquid through or over the metallic surface, or where the metallic surface is in the form of small particles by filtration or magnetism. Where the carrier does not interfere with the assay then it may be left in the assay medium.

The compound may be one of any number of different compounds, such as within a compound collection and as such represents a further feature of the invention.

Typical liquids in which the compound is soluble and are found in common usage for dissolving compounds for testing are typically either aqueous or organic; aqueous systems may include buffered solutions ; organic solvents include protic solvents, such as ethanol, and aprotic solvents, such as DMSO; alternatively the solvent may be a mixture of any of the above solvents. Additional excipients may be added to the liquid to improve the solubility of the compound. We have found that we may arrange the metallic surfaces into a number of different configurations which may be adapted to more particularly be suited to automation, especially automation of compound recovery from the carrier or automatic deposition of compound onto the carrier, or both. For example, by the use of a mat made from a woven mesh of metal fibres, or metal coated non-metal fibres, several compounds may be deposited upon zones of the same mat. The solution of the compound is held, when applied to the surface of the mat, within the weave of fibres. Liquid is allowed to freely evaporate leaving compound adsorbed onto the mat in discrete zones. Compound may be recovered, ideally in an automatic way, by passing a volume of liquid known to dissolve the compound through the mat at the zone in which the compound is stored. Such a system, lends itself easily to automation where computer controlled systems place compound at predetermined positions, the location being logged, and when that compound is required the computer controlled system revisits that same zone after interrogating the log to retrieve the compounds location and retrieves the material in the manner described above.

The same carrier material and the same configuration may be used for the all the compounds, thus leading to a generic use of the technology, or alternatively carriers of the same configuration but in sets of a different material may be used each set being more suited to particular compound types. However, since the configuration of the carrier is the same this also lends easily to the generic use of the technology and, therefore, automation.

In an alternative arrangement carriers having a metal surface, such as fibre, wire, pin, rod, mesh, grid, sheet or strip, are dipped into solutions of compound and removed. Liquid attached to the primer after removal evaporate from the carrier leaving compound adsorbed onto its metal surface. Compound is retrieved by dipping again the carrier into a liquid in which the compound is soluble, or, alternatively, washing the liquid over the carrier. A number of different configurations of the metal surface are anticipated to work. A simple sheet having a metallic surface will work, further treatment of the metal surface could be used, such as to improve the surface area by treatment with such agents to make the surface pitted (such as the use of strong acids), the surface may be contoured so as to form wells or channels through which the liquid may freely flow. Woven metallic fibres may also be used, and are preferred, since these are flexible and may be rolled or even folded, additionally liquid can be forced through the woven materials to recover compound, materials need not be woven but may be a mesh or grid with holes in the sheeting .The carrier may be formed into a free flowing powders by, for example metal fillings.

Suitable metal surfaces are those which are stable and are generally inert to most chemical compounds. Examples include, steel, aluminium, chromium, silver, gold etc.

Presented as a further feature of the invention is a method for storing and dispensing a number of different compounds with different physical properties which comprises (1) adsorbing each compound onto a carrier having a metal surface, (2) storing the adsorbed compounds on the metal surface until a compound is required, (3) extracting the compound from the carrier and (4) dispensing the compound.

Presented as a further feature of the invention is a method of storing a number of different compounds in a compound collection for an extended duration whilst providing for significant recovery of the compound after storage which comprises adsorption of each compound onto a carrier having a metal surface.

A further feature of the invention is a compound collection comprising a number of different compounds wherein each compound has been adsorbed onto a carrier having a metal surface By use of the term "extended duration" we mean that we have found that "recovery" (which means >30% w/w , >50 %w/w, ideally >80% w/w, preferably >90%w/w recovery of the sample) of compound may be extracted from the inert carrier even after a period of storage at room temperature of at least 6 months, and in particular over a period of more than 1 year.

The "number" of compounds in a compound collection which may be stored by the techniques as described above is not limited by the invention, ideally the invention may be used for storage of compounds in compound collections where the number of different compounds stored may be more than 5, 50, 100, 10³, 10" or even more than 10⁶. The invention may also be applied to a subset of a compound collection.

By the use of the term "compounds" we refer to compounds which are able to be adsorbed onto carriers. The physical and chemical properties of the compounds are generally unimportant in applying the present invention. However, it will be appreciated that this method is not suited to compounds with low boiling points. Preferred compounds are those stored in compound collections of pharmaceutical, biotechnology or agrochemical companies. Preferred compounds are organic molecules of molecular weight of less than 2000 Daltons, and ideally of 1000 Daltons or less.

The carrier adsorbed with a compound provides a material with very similar physical properties even when compounds are adsorbed which have different physical properties.. Further advantages include:

Even distribution of compound on inert carrier;

Compound can be quantitatively and reproducibly adsorbed and extracted from inert carrier; Storage and dispensing of compounds which exist normally as liquids, gums or glasses;

Adsorption onto an inert carrier produces metallic material/mesh with very similar handling characteristics;

For the reasons outlined above, robotic handling and weighing of samples is much simpler than for non-adsorbed materials, thereby enabling rapid dispensing of large numbers of compounds; and

Compounds for which only small samples are available can be dispensed far more economically.

The invention is illustrated below by the following no-limiting examples

Examples

Sixteen compounds were selected which spread across physical property space. Parameters considered in the selection were ClogP, molecular volume, number of hydrogen bond donors, number of hydrogen bond acceptors, number of positive charges and number of negative charges. All the parameters were given an equal weighting.

Adsorption of compound onto Inert Supports

10 mM stock solutions in neat DMSO were first made for all 13 compounds. This mimics the format of solubilised compound collection found in many companies. For the stainless steel meshes, pieces of size 150 mm² by 65 μm thick (approx. vol 0.01 ml) were immersed in each of the sixteen 10 mM DMSO solutions. These were then dried in an oven at 60°C to remove DMSO.

Extraction in to aqueous phosphate buffer (O.IM phosphate) pH 7.4

Extraction was carried out by stirring the support for 72 hrs at 25°C in a vial containing 0.1 M phosphate buffer solution, pH 7.4. The aim was to generate an aqueous solution of concentration 10^"5 M, typical of that used in HTS assays. For the stainless steel mesh the calculation is straightforward, we assumed a mesh volume of 0.01 mis, approximately 10 mis of buffer needs to be added. In practise 2 mis was used as a precaution against less adsorption occurring. However the final results were divided by 5 since this turned out not to be the case.

Following 72 hours of stirring the aqueous solutions were analysed using HPLC-UV. The chromatography used is outlined below.

Column: Phenomenex Columbus 3μ C₁₈ 30 mm x 2 mm.

Eluents: Eluent A: Water containing 50 mM ammonium acetate. (Weigh accurately 3.854 g ammonium acetate and dissolve in 1 litre of

Milli-Q deionised water.)

Eluent B: Methanol containing 43.75 mM ammonium acetate.

(Weigh accurately 3.372 g ammonium acetate and dissolve in 1 litre methanol (HPLC Gradient grade)). Flow rate: 1.2 ml/min. Temperature: 50°C.

Detection: 5 wavelengths:- 220, 230, 250, 270 and 320 nm. Gradient:

The results 4 are captured in table 1. Also included in the table are the aqueous solubilities of the 13 compounds in 0.1 M phosphate buffer pH 7.4.

Table 1 - Compound Extraction from Stainless Steel Mesh following 72 hrs Stirring in Phosphate Buffer, pH 7.4

= ea not etecte n u er souton

Claims

1. A method for storing and dispensing a compound, which comprises (1) adsorbing the compound onto a carrier having a metal surface (2) when later required removing the compound from the carrier by contacting liquid, in which the compound is soluble, with the surface of the compound containing carrier and (3) removing the liquid from the carrier.

2. A method as claimed in claim 1 wherein the metal surface is a mat made from a woven mesh of metal fibres, or metal coated non-metal fibres.

3. A method as claimed in claim 2 wherein several compounds are deposited upon zones of the same mat.

4. A method as claimed in claim 2 or claim 3 wherein the compound is removed from the mat by passing a volume of liquid known to dissolve the compound through the mat at the zone in which the compound is stored.

5. A method as claimed in claim 1 wherein the carrier having a metal surface is a fibre, wire, pin, rod, mesh, grid, powder sheet or strip.

6. A method as claimed in any preceding claim wherein the metal surface is steel, aluminium, chromium, silver or gold.

7. A method for storing and dispensing a number of different compounds with different physical properties which comprises (1) adsorbing each compound onto a carrier having a metal surface, (2) storing the adsorbed compounds on the metal surface until a compound is required, (3) extracting the compound from the carrier and (4) dispensing the compound.

8. A compound collection comprising a number of different compounds wherein each compound has been adsorbed onto a carrier having a metal surface.

9. A compound collection as claimed in claim 8 wherein the number of different compounds is more than 100.