Method of Controlling a Polypeptide Modification Reaction
The invention relates to a method of controlling a polypeptide modification reaction, in particular but not exclusively, a method of controlling the activation of human factor VII (FVII) to produce human factor VII(a) (FVII(a)). The invention also relates to polypeptides obtainable by the polypeptide modification reaction and to pharmaceutical compositions comprising said polypeptides.
1 . A method of activating a serine protease blood coagulation factor which comprises the steps of:
(a) measuring the initial concentration of the serine protease blood coagulation factor;
(b) measuring the initial proportion of activated serine protease blood coagulation factor;
(c) calculating the serine protease blood coagulation factor activation reaction time by correlation of the values measured in each of steps (a) and (b) with a value of required proportion of activated serine protease blood coagulation factor; and
(d) performing the serine protease blood coagulation factor activation reaction for the time calculated in step (c);
(e) terminating the reaction after the reaction time calculated in step (c).
2 . The method according to claim 1 , wherein the reaction time, T, in step (c) is calculated in accordance with formula (I):
t
=
-
ln
(
akt
0
·
(
akt
-
1
)
akt
·
(
akt
0
-
1
)
)
k
(
T
)
·
xb
·
F
0
(
I
)
wherein “akt” refers to the required proportion of cleaved polypeptide, “akt0” refers to the initial proportion of cleaved polypeptide measured in step (b), “F0” refers to the initial concentration of the polypeptide (in g/l) measured in step (a), k(T) refers to the reaction constant for the given reaction (in L/g/min) as a function of temperature, T, and xb refers to the molar fraction.
3 . The method according to claim 2 , wherein k(T) is a polynomial or a spline.
4 . The method according to claim 1 wherein the correlation procedure described in step (c) is calculated in accordance with formula (II):
t
=
-
ln
(
akt
0
·
(
akt
-
1
)
akt
·
(
akt
0
-
1
)
)
k
·
xb
·
F
0
(
II
)
wherein “akt” refers to the required proportion of cleaved polypeptide, “akt0” refers to the initial proportion of cleaved polypeptide measured in step (b), k is the reaction constant, xb refers to the molar fraction, “F0” refers to the initial concentration of the polypeptide (in g/l) measured in step (a).
5 . The method according to claim 4 , wherein k=0.29.
6 . The method according to claim 2 or claim 4 , wherein xb=1.
7 . A method of preventing degradation of an activated serine protease blood coagulation factor, said method comprising the steps of:
(a) measuring the initial concentration of the serine protease blood coagulation factor;
(b) measuring the initial proportion of activated serine protease blood coagulation factor;
(c) calculating the serine protease blood coagulation factor activation reaction time by correlation of the values measured in each of steps (a) and (b) with a value of required proportion of activated serine protease blood coagulation factor; and
(d) performing the serine protease blood coagulation factor activation reaction for the time calculated in step (c);
(e) terminating the reaction after the reaction time calculated in step (c).
8 . The method according to claim 1 , wherein said serine protease is factor VII, a factor VII analogue or derivative thereof, or factor IX.
9 . The method according to claim 8 wherein said factor VII analogue is V158D/E296V/M298Q-FVII(a).
10 . The method according to claim 1 wherein the required proportion of cleavage will be between 90 and 99%, between 94 and 99%, between 95 and 97%, between 96 and 98%, or between 97 and 99%.
11 . The method according to claim 1 wherein the cleavage reaction additionally comprises the addition of calcium ions.
12 . A method as defined in claim 1 wherein the activation reaction is performed at a pH of between 6.0 and 8.0.
13 . A method as defined in claim 1 wherein termination comprises lowering the pH to a value below about 6.0.
14 . A serine protease obtainable according to the method as defined in claim 1 .
15 . A composition comprising an activated factor VII(a) analogue, or derivative thereof, obtainable according to the method as defined in claim 1 .