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Polymorphs: new forms of known compounds?

  • 02 December 2009
  • Articles

One of the challenges faced by the pharmaceutical industry is achieving better results in terms of the bioavailability of pharmacologically active compounds. This could be achieved thanks to the polymorphic properties of certain drugs.

Polymorphism can be defined as a molecules ability to adopt different spatial packing forms (crystallisation) due to the specific physicochemical conditions to which it is subjected.

Until now it has not been possible to predict the way in which a compound might crystallise.

Likewise, it has not yet been established how pharmacokinetic and therapeutic conditions may be affected by different crystalline forms of the same compound, as it has been found that new polymorphs can have adverse effects, including side effects and a reduction in solubility and toxicity.

When a crystalline form that complies with all of the aforementioned requirements is achieved, the pharmaceutical industry seeks to protect it using a patent of invention.

Multinational pharmaceutical companies attempt to characterise each form using intensity patterns resulting from the location of atoms within the crystal, which are measured using the x-ray diffraction method.

In certain Latin American countries there has been controversy as to whether or not such forms meet patentability requirements: novelty, inventive step and industrial application.

In Colombia, novelty and industrial application have been recognised. However, the national office questions the existence of inventive step on the basis of the “obviousness” of the processes used to obtain these forms, since they are based on crystallisation.

The national office has established that crystallisation is a very well-known method and that the only thing that an expert does is change conditions such as the temperature, solvents and saturation of the solution to achieve a different form of a known compound.

This practice dismisses the research conducted by multinationals in the field of new crystalline forms that seek to improve patients quality of life.

However, the investigators creativity goes beyond merely changing the physicochemical crystallisation conditions; the innovation lies in designing appropriate and specific conditions that not only ensure that the crystallisation produces a unique crystalline form, but also that enable the process to be reproduced on an industrial scale.

It is important to consider that when a specific, appropriate crystalline form is found, it must comply with all the patentability requirements.

It seems that the patentability of new forms of known compounds in countries such as Colombia is not only related to technical requirements. Even when such forms comply with the patentability requirements, achieving patents for them could apparently lead to conflicts with pharmaceutical companies that produce generic medicinal products.

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