Chemistry Reference
In-Depth Information
Amorphous solids, lacking the three-dimensional long-range order of a crystalline
material, possess a more random arrangement of molecules, exhibit short-range order
over a few molecular dimensions, and have physical properties quite different from those
of their corresponding crystalline states [2]. It has been reported, however, that just what
the truly
state looks like in terms of molecular ordering is more complex
than it may seem [3]. This can introduce ambiguity into the patent claims. For patenting
purposes, then, the de
“
amorphous
”
nition of
“
amorphous
”
takes a slightly different focus. Inventors
and patent drafters want to de
in
such a way that it is clear and that patent infringement can be readily proved. One does
not want to overburden the claim with excessive limitations that may be easily avoided
by competitors or hard to prove for infringement. Rather, the definition of amorphous
(actually any de
ne
“
amorphous
”
and
“
amorphous solid dispersion
”
ned term) should be one that is readily understandable, accessible, and
provable for infringement purposes. This is where the patent law permits an inventor to
de
ne terms, to be his/her own lexicographer can be used to advantage. Thus, the
de
may vary somewhat from patent to patent and be designed to
meet the needs of the amorphous solid dispersion.
In an amorphous solid dispersion patent, the speci
nition of
“
amorphous
”
cation will contain a de
nition of
what it means to be
and will also provide at least one measure of how to
determine that the composition is, in fact, an amorphous solid dispersion. The particular
de
“
amorphous
”
will often depend on the technique(s) employed by the
inventor to characterize the amorphous sold dispersion. To adequately de
nition of
“
amorphous
”
ne a patent-
able invention, and provide proof of infringement, the de
nition of
“
amorphous
”
or
“
should contain objectively measurable aspects. Those
objectively measurable aspects can be used to de
amorphous sold dispersion
”
cation and/or as
claim limitations to delineate and set out the invention to be patented. For an amorphous
solid dispersion, this means adding at least one objectively measurable element to the
de
ne terms in the speci
nition by which one of ordinary skill can determine whether or not the combination of
an API and matrix material is an amorphous solid dispersion of the invention. The
de
nition of an amorphous solid dispersion typically relies on an analytical technique to
provide an objectively measurable indicator of the amorphous state of the API within the
solid dispersion.
A number of techniques have been used to characterize amorphous solid dispersions
and determine the solid state of the API within the dispersion. The more common
techniques include X-ray powder diffraction (XRPD), differential scanning calorimetry
(DSC), and solid-state NMR (SSNMR) [4]. Each of these techniques can differentiate an
amorphous solid from its crystalline counterpart. Perhaps the most common technique is
XRPD that is used both for crystalline solids and for amorphous solids and is familiar to
patent examiners. Thus, as an example, an inventive amorphous solid dispersion
characterized by XRPD could be described in this way:
The invention relates to amorphous solid dispersions of amorphous [API] in a [polymer
matrix]. The amorphous nature of the solid dispersions is determined by X-ray powder
diffraction (XRPD). A material is
when there are no sharp peaks
observed in its XRPD pattern, only broad halos. Sharp peaks in the XRPD indicate the
presence of crystalline material.
“
X-ray amorphous
”
