Exercise XI – 2016
IPIC PATENT AGENT TRAINING COURSE
MODULE 2 – INFRINGEMENT & VALIDITY
EXERCISE XI – INFRINGEMENT
Sustained Release Formulation
Dear Patent Agent,
Our company is planning to make a formulation of propanolol to sell to pharmacies in Canada. Our
development department has come up with two formulations which are set out below.
In version #1, we have used HPMC which causes the formulation to release the drug slowly into the
system (and thus provide sustained release). The HPMC polymer together with the drug and other
pharmaceutically acceptable excipients/ingredients are combined in the form of a tablet. When the
dosage form is placed in an aqueous environment as occurs in the body, the HPMC polymer hydrates and
swells as water molecules penetrate the matrix. At the same time, the drug undergoes dissolution in the
aqueous environment. A concentration gradient is immediately created since the concentration of drug
inside the matrix is higher than it is outside the matrix. The concentration gradient drives the drug out of
the matrix by diffusion. However, the swollen polymer creates a barrier to diffusion of the drug (gel
layer) and it is this property of HPMC which retards the movement of the drug out of the matrix and
allows for control over the rate of drug release from the matrix.
In version #2, we use carboxypolymethylene which is a water insoluble polymer. Insoluble polymers that
form “skeletal” structures from which drug diffuses out into the surrounding medium. The rate limiting
step in controlling release from these formulations is liquid penetration into the matrix unless channelling
(wetting) agents are included to promote permeation of the polymer matrix by water, which allows drug
dissolution and diffusion from the channels created in the matrix.
In version #1 we have included a loading dose of propanolol which will release immediately upon
dissolution in the stomach. Version #2 does not have a loading dose, but we have found some trace
amounts of propanolol in the coating. Our in-house expert in pharmacokinetics advises that trace
amounts will not provide immediate release of propanolol.
Our current product monograph lists the uses of our formulation as treatment of coronary artery disease,
migraine, anxiety and tremors. Our marketing information will list these uses.
We are aware of Patent No. 2,XXX,XXX issued to Big Pharma Co. on June 6, 2009. It was published on
June 15, 2008 and was filed on June 4, 2007 in Canada claiming a priority to a U.S. filing on June 5,
2006. Can you please advise:
1.
(a) Do our versions infringe Canadian Patent No. 2,XXX,XXX?
(b) Which version do you recommend that we market?
(c) Does it make a difference if HPMC was invented in 2010?
2.
Do we infringe the use claim – Claim 6? How can we avoid infringement?
Yours Truly,
G. Smith
President, Small Pharma Inc.
1
Exercise XI – 2016
Sustained Release Formulation
Version #1
Version #2
Compressed Core
% by weight of core
% by weight of core
Propanolol
50%
50%
HPMC (soluble polymer which 20%
works
differently
than
carboxypolymethylene)
0
Carboxypolymethylene
0%
15%
zinc oxide
1.5%
1.5%
stearic acid
5%
2%
mannitol
20%
0
microcrystalline cellulose
3.5%
36.5
Yes
Yes
Yes
Trace amounts of propanolol
Seal Coating surrounding the
core
Polyvinylacetate phthalate
Sugar Coating surrounding the
seal coated core
Loading Dose of Propanolol
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
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