Present invention is related to a novel process of isolation, purification and production of
tissue plasminogen activator (TNK-tPA) from mammalian cells, more specifically from
Chinese Hamster Ovary (CHO) cells.
BACKGROUND OF THE INVENTION
Tenecteplase (TNK-tPA) is a recombinant glycoprotein of serine protease family with six
amino acids substitution in the native human tissue plasminogen activator (t-PA) with 17
disulphide bridges and having molecular weight of ~67kDa. In the development of TNK-tPA,
the modifications made in native t-PA includes substitution of threonine 103 with asparagine,
substitution of asparagine 117 with glutamine both within the kringle 1 domain, and the
substitution of lysine, histidine and two arginine with tetra-alanine amino acids at 296-299
positions in the protease domain to make the resulting protein highly fibrin specific with
longer plasma half life and 80% decreased susceptibility to degradation by plasminogen
activator inhibitor- 1 (PAI-1) compared to native t-PA.
The TNK in TNK-TPA refers to the sites of the t-PA molecule that have been modified
i.e.T103; N117; and KHRR 296-299.The aforementioned modifications of TNK-tPA renders
its use as an improved therapeutic agent for the treatment of acute myocardial infarction
which has better therapeutic compliance because the greater fibrin specificity allows for
faster and complete clot lysis with decreased bleeding complications and the long life-span
permits a single bolus dose with less systemic fibrinolysis and lesser bleeding complications
from the previous clot buster drugs.
The mechanism of TNK-tPA is initiated on binding of TNK-tPA to the fibrin component of
the thrombus (blood clot) which selectively converts inalctive plasminogen into plasmin and
consequently the resultant plasmin degrades the matrix of thrombus in occluded artery while
conserving fibrinogen and minimizing systemic plasminogen activation due to its highly
specific nature.
The benefits of TNK-tPA seen in myocardial infarction patients and the encouraging results
from animal studies in the context of Acute Ischemic Stroke (AIS), suggested that TNK-tPA
might prove to be a safer and more effective therapy than alteplase, the only drug approved
by USFDA for AIS. Over the past few years, several clinical trials evaluated the use of TNKtPA
in AIS and proved that TNK-tPA has a better pharmacological profile than alteplase and
also suggested that it could be an effective and safe therapeutic option in treating AIS in
patients reporting within 4.5 h after symptom onset. Recently, TNK-tPA has been considered
for the treatment of patients with pulmonary embolism and several clinical trials showed
promising outcomes. A large number of clinical trials are still being conducted to assess the
complete conclusive picture of TNK-tPA in several indications.
In the last few years, development and manufacturing of recombinant glycoproteins was
carried out by batch, fed batch semi-fed batch and perfusion bioreactors processes and for
purification of these proteins adsorption and ion exchange chromatography were majorly
employed.
For t-PA and its variants certain purification protocols are known in prior art e.g. purification
by immuno affinity (anti-tPA goat polyclonal antibody), ion exchange, ethanol precipitation,
reverse phase chromatography, chromatography on silica or anion exchange, such as
diethylamino ethyl, ammonium sulphate precipitation, sephadex- G-75 etc.
Some of the approaches for the purification of TNK t-PA is listed in prior art includes WO
201 1/015922, sets out a purification process where series of ion exchange chromatography
steps, immunoaffinity chromatography and ultrafiltration/diafillration steps are used for
purification of TNK-tPA. WO 2012/066569 A, sets out a purification process primarily
drawn to the use of hydrophobic interaction chromatography.
The immune affinity chromatography used in the prior art is no suitable technique for
commercial manufacturing of TNK-tPA. Not only it could raise lot of regulatory concerns
but the cost of immune affinity chromatography media is also very high compared to
conventional chromatography matrices owing to their use of monoclonal antibodies fo
preparation. Hydrophobic interaction chromatography described in certain prior art for TNKtPA
purification uses isopropyl alcohol (IPA) in the process which is an organic solvent and
known for inducing aggregation and denaturation of proteins and may be considered as one
of the disadvantages of the prior a . TNK-tPA is a highly unstable molecule and hence use of
PA in the purification process should be avoided as it may lead to the denaturatlon of the
protein. In addition, the large volume usage of IPA at commercial scale would require
recycling of IPA which again demands additional energy consumption and extra investment
such as solvent recovery unit.
Therefore, none of the aforementioned processes a e capable of providing an efficient,
scalable and robust purification solution, which could consistently produce TNK-tPA drug
substance a commercial scale, meeting al the required specifications.
Hence, there is a need for an effective and commercially viable process for purification of
TNK-tPA.
OBJECT OF THE INVENTION
The object of the present invention is to develop an efficient, robust, scalable, and
commercially viable purification process for the production of TNK-tPA resulting yield not
less than 60% and purity more than 95% as measured by Size exclusion chromatography.
SUMMARY OF THE INVENTION
The present invention relates to a novel process of isolating and purifying tissue plasminogen
activator and its variants more specifically TNK-tPA from CHO cells and describes an
industrially applicable, simple, cost effective, robust and highly efficient process of TNK-tPA
purification.
A process for isolation and purification of TNK-tPA of the present invention comprising
steps of:
i) subjecting cell free harvest obtained from CHO cell culture to affinity
chromatography to capture TNK-tPA and obtaining an eluate containing
partially purified TNK-tPA.
(ii) subjecting the eluate of step (i) to affinity chromatography for additional
purification of TNK-tPA and obtain an eluate containing primarily TNK-tPA.
(iii) viral inactivation of eluate of step (ii) to obtain the viral inactivated sample;
(iv) subjecting the viral inactivated sample of step (iii) to a further affinity
chromatography for additional purification to obtain an eluate containing
primarily highly purified TNK-tPA;
(v) subjecting the eluate of step (iv) to cation exchange chromatography to obtain
an eluate containing highly purified preparation of TNK-tPA;
(vi) subjecting the eluate of step (v) to virus reduction filtration for removal of
virus present;
(vii) concentrating the sample of step (vi) to obtain TNK- tPA; wherein the yield of
the process is more than 60 % and purity of TNK-tPA obtained is more than
95% as measured by Size exclusion chromatography.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1: Depicts a chromatogram of affinity-I purification where first peak represents
impurities and second peak corresponds to eluate containing TNK-tPA.
Figure 2: Depicts a SDS PAGE (silver stained) profile of affinity-I purification where lane
no 5, 6 and 7 showing wash fractions ( 2 and 3 respectively) and Lane No. 9 corresponds to
eluate containing TNK-tPA.
Figure 3: Depicts a chromatogram of affinity- II purification, UV 280 peak corresponding to
eluate containing TNK-tPA.
Figure 4: Depicts a SDS PAGE (silver stained) profile of affinity-II purification where lane
No. 9 corresponds to eluate containing TNK-tPA
Figure 5: Depicts a chromatogram of affinity- III purifi cation UV 280 peak (first)
corresponds to eluate containing TNK-tPA
Figure 6: Depicts a SDS PAGE (silver stained) profile of affinity-Ill purification where lane
No. 9 corresponds to eluate containing TNK-tPA
Figure 7: Depicts a chromatogram of cation exchange purification, UV 280 peak corresponds
to eluate containing TNK-tPA.
Figure 8; Depicts a SDS PAGE (silver stained) profile of cation exchange purification where
lane No. 5 corresponds to eluate containing TNK-tPA
Figure Depicts a comparison of reducing SDS-PAGE (silver stained) profile of drug
substance obtained after purification using steps described in present invention and innovator
product (Metalyse).
Figure 10: Depicts a comparison of non reducing SDS PAGE (silver stained) profile of drag
substance obtained after purification using steps described in present invention and innovator
product (Metalyse).
Figure 11: Depicts a peptide map chromatogram of drug substance obtained after
purification using step described in present invention resembles with innovator product
(Metalyse)
Figure 12: Depicts a immune blotting of drug substance obtained after purification using
steps described in present invention resembles with innovator product (Metalyse)
Figure 13: Depicts the breakthrough curve of Affinity-I (Blue Sepahrose FF) in batch mode.
Figure 14: Depicts Chromatograms for the PCC run over two cycles for (a) Column A -first
column in the loading zone ; (b) Column B - the second column in the loading zone ; (c)
Column C - the third column in the loading zone. ; (d) Column chromatograms superimposed
on each other showing full PCC run. UV is measured at 280 nm. Run performed on an
XK16-5ml Blue Sepharose Fast Flow.
Figure 15: Depicts Chromatogram from the first column (Column A) overloading and
capture in Column B, UV measured at 280 nm. Run performed on an 16-5ml B ue
Sepharose Fast Flow.
Figure 16: Depicts Chromatogram from the third column (Column C) showing all post load
washing. Impact of wash steps are denoted by A - Wash 1, B- Wash 2, C- wash 3, D -
Elution, E- Regeneration 1, F- Regeneration 2, G-Regeneration 3, H-Regeneration 4. UV
measured at 280 nm. Run performed on an XK16-5ml Blue Sepharose Fast Flow.
DETAILED DESCRIPTION OF INVENTION
The present invention relates to a novel process of isolating and purifying tissue plasminogen
activator and its variants more specifically TNK-tPA. The cell free harvest is obtained from
the cells cultured in bioreactors. The list of symbols and abbreviations used in specification
of the present invention are listed at Table A below:
Table A: List of symbols and abbreviations
tPA Tissue Plasminogen Activator
CHO Chinese Hamster Ovary
kDa Kilo-Dalton
PAI Plasminogen Activator Inhibitor
AIS Acute Ischemic Stroke
SDS PAGE Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis
PA Isopropyl Alcohol
CHT Ceramic Hydroxy Apatite
FF Fast Flow
n M Milli Molar
MTX Methotrexate
EACA Epsilon-aminocaproic acid
MES- Hydrate 2-(N-Morpholino) ethanesulfonic acid hydrate
TFF Tangential Flow Filtration
UF Ultrafiltration
DF Diafiltration
PES Polyethersulphone
PVDF Polyvinylidene Fluoride
m Micron or Micrometer
XMuLV Xenotropic Murine Leukemia Virus
PRV Pseudorabies Virus
Reo-3 Reovirus Type 3
MMV Murine Minute Virus
CV Column Volume
DBC Dynamic Binding Capacity
HCP Host Cell Protein
DNA De-oxyribo Nucleic Acid
HCD Host Cell DNA
SEC- HPLC Size Exclusion Chromatography
HPLC High Performance Liquid Chromatography
LAL Limulous Amoebocyte Lysate
u v Ultraviolet
MMC Mixed Mode Chromatography
The present invention relates to a novel process of isolating and purifying tissue plasminogen
activator and its variants more specifically TNK-tPA from CHO cells and describes an
industrially applicable, simple, cost effective, robust and highly efficient process of TNK-tPA
purification
A process for isolation and purification of TNK-tPA of the present invention comprising
steps of:
i) subjecting cell free harvest obtained from CHO cell culture to affinity
chromatography to capture TNK-tPA and obtaining an eluate containing
partially purified TNK-tPA.
(ii) subjecting the eluate of step (i) to affinity chromatography for additional
purification of TNK-tPA and obtain an eluate containing primarily TNK-tPA.
(iii) viral inactivation of eluate of step (ii) to obtain the viral inactivated sample;
(iv) subjecting the viral inactivated sample of step (iii) to a further affinity
chromatography for additional purification to obtain an eluate containing
primarily highly purified TNK-tPA;
(v) subjecting the eluate of step (iv) to cation exchange chromatography to obtain
an eluate containing highly purified preparation of TNK-tPA;
(vi) subjecting the eluate of step (v) to virus reduction filtration for removal of
virus present;
(vii) concentrating the sample of step (vi) to obtain TNK- tPA; wherein the yield of
the process is more than 60 % and purity of TNK-tPA obtained is more than
95% as measured by Size exclusion chromatography.
The process of the present invention may be explained by illustrating the steps as below:
(i) Subjecting cell free harvest obtained from CHO cell culture to affinity
chromatography to capture TNK-tPA and obtaining an eluate containing
partially purified TNK-tPA.
The cell free harvest containing TNK-tPA may be obtained from perfusion technology
based fermentation system by CHO cells. The harvest containing TNK-tPA may be
filtered with 0.2 m and collected in sterile containers and stored at 2-8°C till further
use. The cell free harvest containing TNK-tPA is subjected to affinity
chromatography. The stationary phase of affinity chromatography may be selected
from the group comprising Blue Sepharose 6 fast flow, Lysine Hyper D, Ceramic
Hydroxy Apatite (CHT), preferably the stationary phase is Blue Sepharose 6 FF. The
column may be equilibrated by using a buffer comprising Phosphate buffer, sodium
chloride and polysorbate 20 or their mixtures. The elution buffer or mobile phase
employed for capture step (Affinity Chromatography) may be individually or in
combination selected from phosphate buffer, urea, and sodium chloride. More
preferably, the elution buffer or mobile phase is used in combination. The
concentration of sodium phosphate in buffer used is preferably 20-50 mM sodium
phosphate, more preferably 20-40mM. The concentration of sodium chloride used in
the buffer is 1-2.5 M NaCl, more preferably 1.5-2M.The concentration of urea in the
buffer may be in the range of 1-4 molar, preferably in the range of 2-3 molar. The pH
of the elution buffer or mobile phase may be maintained in the range of 7-8,
preferably in the range of 7-7.6, more preferably in the range of 7.2-7.4.
The removal of host cell proteins from products produced in mammalian cells is
always a difficult task. In the present invention the step optimized as capture
chromatography in current invention selectively removes host cell proteins to an
extent of 0.8 to 1.5 log, more specifically 1.0 log which helps in achieving final
concentration of HCP in purified TNK-tPA preparation, below 100 ppm.
Not only the host cell proteins (HCP) are reduced but process related impurities such
as albumin, gentamycin, Methotrexate (MTX) etc. are also removed effectively by the
capture chromatography described in present invention.
Subjecting the eluate of step (i) to affinity chromatography for additional
purification of TNK-tPA to obtain an eluate containing primarily TNK-tPA.
The eluate of step (i) may be subjected to affinity chromatography. The stationary
phase or column material may be selected from the group comprising of Blue
Sepharose 6 fast flow, Lysine Hyper D, Ceramic Hydroxy Apatite (CHT), etc.,
preferably the stationary phase is Lysine Hyper D. The equilibration buffer employed
in Affinity chromatography step may be individually or in combination selected from
Phosphate buffer, sodium chloride and polysorbate. More preferably the equilibration
buffer is used in combination.
The column may be eluted by a elution buffer or mobile phase selected from the
group comprising individually or in combination selected from sodium acetate, urea
and Epsilon-aminocaproic acid (EACA). The pH of the affinity chromatography
elution buffer may be done in the range of pH 3.5-6, preferably 4-5, more preferably
4.5-5.
The chromatography matrix employed for intermediate purification e.g. Affinity-II
chromatography step may be selected from the group comprising of Blue Sepharose 6
fast flow, Lysine Hyper D and Ceramic Hydroxy Apatite (CHT), preferably the
chromatography matrix used is Lysine Hyper D.
The elution buffer employed in Affinity chromatography step may be 5-25 mM
sodium acetate, 1-4 M urea, 0.1-0.4 M EACA having pH 4.0-5.0. The concentration
of sodium acetate in elution buffer is 5-25 mM, preferably in the range of 5-15 mM.
The concentration of EACA in the buffer is 0.1-0.4 mM, preferably in the range of
0.1-0.2 M. The concentration of urea is 1-4 M in the buffer, preferably in the range of
2-3 M.
The inventive merit of elution buffer by using EACA at acidic pH in this step is to
provide the most suitable condition. The process of the present invention as set out
herein is most suitable for viral inactivation and reduces the handling and material
consumption by several folds. Approximately 2-4 log reduction of viral clearance and
1-1.5 log reduction of host cell proteins (HCP) are achieved by Affinity
chromatography used in present invention. On an average the 1.69 log reduction with
XMuLV and 4.30 log reduction with PRV are achieved by Affinity chromatography
used in present invention.
Viral inactivation of eluate of step (ii) to obtain the viral inactivated sample;
The viral inactivation of the eluate obtain from step (ii) may be conducted by any
method such as heat treatment (Pasteurization, Lyophilisation/dry heat), irradiation,
ultraviolet (UV), high hydrostatic pressure, low pH incubation, chemical and
solvent/detergent treatments. Chemical inactivation or viral inactivation is done by
treating the sample with chemical selected from the group comprising sodium cholate,
triton, Beta-propiolactone, tri(n-butyl)phosphate (TNBP), and sodium caprylate,
preferably treating the sample with sodium caprylate at low pH in the presence of
Urea. The concentration of chemical/detergent is in the range of 0.001% to 0.10%
w/v, preferably 0.01% - 0.07% (w/v), more preferably 0.05%.The concentration of
urea is used in the range of 1-4 M, preferably 2-3 M. The viral activation may also be
carried out by incubating the sample for a period of 40-180 minutes, more preferably
for a period of 40-80 minutes, in the temperature range of 15-45°C, more preferably
in the range of 20-30°C.
Generally low pH is the choice and most widely used method of viral inactivation in
purification processes. Low pH is known to inactivate enveloped viruses but it cannot
inactivate highly resistant non enveloped viruses. The pH is in range from 4.0 to 4.7,
more preferably in range from 4.3 to 4.7.
The composition of viral inactivation buffer described in present invention is
optimized in such a manner that it could inactivate both enveloped and non enveloped
viruses efficiently. Use of the chemicals/detergents, urea, EACA and low pH of the
present invention makes the conditions lethal for enveloped and non enveloped
viruses and makes the combination an optimum choice for inactivating highly
resistant viruses. On an average 5.65 log reduction with XMuLV and 5.38 log
reduction with PRV are achieved by low pH and chemical inactivation of the present
invention.
Subjecting the viral inactivated sample of step (iii) to a further affinity
chromatography to obtain an eluate containing TNK-tPA;
The viral inactivated sample of step (iii) may be subjected to a further affinity
chromatography. The stationary phase or column material of affinity chromatography
may be selected from the group of Blue Sepharose 6 fast flow, Lysine Hyper D,
Ceramic Hydroxy Apatite (CHT), etc., preferably the stationary phase or
chromatography matrix used is Ceramic Hydroxy Apatite (CHT). The stationary
phase or column may be eluted by a mobile phase or buffer selected from the group
comprising individually or in combination selected from Phosphate buffer, 2-(NMorpholino)
ethanesulfonic acid hydrate (MES- Hydrate), sodium chloride and urea.
The pH of the affinity chromatography elution buffer may be done at pH ranging from
6-9, preferably 6-8, more preferably 6-7.
The mobile phase or elution buffer employed in Affinity chromatography step may be
5-50 mM phospahte buffer, preferably in the range of 5-15 mM. The concentration of
urea is used in the range of 1-4 M in buffer, preferably in the range of 1-3 M. The
concentration of MES- Hydrate used may be 2-20 mM in the buffer. Elution may be
carried by increasing concentration of salt. The salt of this elution may be selected
from group of potassium chloride, sodium chloride, sodium phosphate and
ammonium sulphate, preferably the salt is sodium chloride and concentration of
sodium chloride is in range of 0.1-1.0 M sodium chloride. The elution type may be
linear, step or in combination of both, preferably the elution used is linear salt
gradient.
Affinity chromatography (multimode chromatography) used in present invention is to
remove traces of impurities, specifically host cell DNA (HCD), host cell
proteins(HCP) and viral impurities if any. Approximately 2-4 log reduction of viral
clearance and 0.5 - 1 log reduction of HCP is achieved using affinity-Ill
chromatography mentioned in current invention. On an average 4.23 log reduction
with XMuLV, 4.06 log reduction with PRV, 3.73 log reduction with Reo-3 and 2.97
log reduction with MMV are achieved by Affinity chromatography used in present
invention.
Subjecting the eluate of step (iv) to cation exchange chromatography to obtain
an eluate containing highly purified preparation of TNK-tPA in formulation
buffer;
The cation exchange chromatography of the eluate of step (iv) may be conducted by
using a matrix or stationary phase selected from the group comprising Fractogel S0 3,
Fratogel SE Hicap, SP Sepharose FF, CM Sepharose FF etc., preferably the
chromatography matrix or stationary phase used is Fractogel SO3. The equilibration
buffer employed in cation exchange chromatography may be individually or in
combination selected from group comprising phosphate buffer, urea, MES and
sodium chloride, preferably the equilibration buffer is used in combination.
The elution buffer or mobile phase employed in cation exchange chromatography
may be individually or in combination selected from L-Arginine, O-phosphoric acid
and polysorbate-20, preferably, the elution buffer is used in combination or mixture.
The mobile phase or elution buffer employed in cation exchange chromatography
comprising L-Arginine present in range from 10-350 mM, preferably in range from
250-350 mM, O-phosphoric acid present in range from 0.5-1%, preferably in range
from 0.6%-0.8% and polysorbate-20 present in range from 0.01-0.05%, preferably in
range from 0.04 to 0.05 % . The pH of the cation exchange chromatography elution
buffer or mobile phase may be done in the range of 7.0 to 7.5, preferably in the range
7.3- 7.5.
Generally the ion exchange chromatography is used as capture, intermediate and
polishing chromatography to either remove bulk or traces of impurities. In present
invention the cation exchange chromatography is somewhat used differently than it is
conventionally used. Herein, the eluate of previous chromatography is directly loaded
on to cation exchange chromatography to obtain the highly purified preparation of
TNK-tPA in final formulation buffer containing arginine, orthophosphoric acid and
polysorbate 20. The advantage of using cation exchange chromatography differently
is that buffer exchange and simultaneous concentration and purification are achieved
in a single step. In prior art techniques like gel filtration chromatography and
diafiltration using Tangential Flow Filtration (TFF) are employed for buffer
exchange. These techniques are efficient and most commonly used for buffer
exchange but cannot further purify target protein. Due to the fact that one can only
load maximum 30% of sample to column volume in gel filtration chromatography,
bigger size of columns are required compared to ion exchange chromatography. Gel
filtration chromatography also causes the dilution of target protein during buffer
exchange which further requires some additional concentration step like TFF. Buffer
exchange using diafiltration is also not feasible when volumes to be buffer exchanged
are higher since it requires very high amount of buffer and demands large size of
UF/DF unit. Considering aforementioned limitations of conventional buffer exchange
techniques the cation exchange chromatography described in present invention is
capable to provides a buffer exchange step and assists in further purification also. It is
possible to achieve a viral reduction factor of 1.21 log with non enveloped virus e.g.
MMV using ion exchange chromatography of the present invention.
subjecting the eluate of step (v) to virus reduction filtration for removal of virus
present;
The virus filtration may be performed after affinity chromatography, cation exchange
chromatography, and tangential flow filtration step, more preferably the virus
filtration step is performed after cation exchange chromatography. Nanofilter selected
for this step may be of 15 nm, 20 nm, and higher. Preferably the nanofilter size is
between 15- 20 nm. The nanofilter used may be made up of cellulose, PES, PVDF
etc. More preferably the filter used is PES.
The filtration performed after virus filtration may be selected from microfiltration,
ultra filtration, nano filtration, macro filtration, tangential flow filtration, etc. More
preferably the filtration is tangential flow filtration. On an average 4.15 log reduction
with XMuLV, 3.40 log reduction with PRV, 4.41 log reduction with Reo-3, 4.76 log
reduction with MMV are achieved by virus reduction filtration used in present
invention.
The Overall downstream process provides more than 15 log reduction with XMuLV,
more than 17 log reduction with PRV, more than 8 log reduction with Reo-3, and
more than 8 log reduction with MMV.
The most probable contaminant in the process of TNK t-PA would be CHO cell
derived retrovirus and XMuLV represents a non-defective C type retrovirus for CHO
cells, a more than 15 log reduction obtained for XMuLV is considered most relevant
and gives a high assurance in terms of viral safety.
Concentrating the sample of step (vi) to obtain TNK-tPA.
The filtrate obtained in step (vii) is subjected to filtration method selected from the
group comprising microfiltration, ultrafiltration, nanofiltration, microfiltration and
tangential flow filtration, preferably the filtration method is tangential flow filtration.
Ultra filtration membrane selected for this step may be of 5, 10, 30 or 50kDa.
Preferably the ultra filtration membrane used is in the range of 5-30 kDa, more
preferably the size of ultra filtration membrane used is 10 kDa. The Ultra filtration
membrane used may be made up of cellulose, PES, PVDF etc. More preferably the
filter used is PES. The concentration of TNK-tPA retentate may be in the range of
1.0+0.4mg/ml to 7.0+0.4mg/ml. More preferably, the concentration of TNK-tPA may
be in the range of 1.0+0.4mg/ml to 6.0+0.4mg/ml. Most preferably, the concentration
of TNK-tPA is 5.5+0.4mg/ml.
The TNK-tPA drug substance (Tenecteplase) may preferably be obtained by sterile
filtration of TFF Retentate using 0.2 m sterilizing grade filters made up of PES,
PVDF, and Cellulose. More preferably sterile filter is made up of PES.
The present invention also discloses a process, wherein the batch Affinity-I
chromatography may also be operated in continuous mode using periodic counter
current chromatography (PCC). The use of PCC, provides additional advantage e.g.
reduced buffer consumption, increased productivity, steady state operation and better
process controls. .
The present invention, includes within its scope, the use of inline buffer and
chromatography load conditioning cum preparation by five pump based customized
AKTA process system with a maximum flow rate of 600 L/h. The said activity can be
performed by Flow feedback or pH-Flow feedback mode of control for buffer and
chromatography load preparation of Affinity-I, II, III and IEC chromatography steps
as mentioned in Example 1 to 4.
The process of the present invention results in a purified product of TNK-tPA with
increased yield and purity. The attributes of TNK-tPA obtained by the process of the
present invention is set out in detail at Table B.
Table B: Results pertaining to Quality of TNK-tPA
S.No. Critical Quality Attribute Quality of Purified TNK-tPA BULK
1 Appearance Clear colorless to slightly yellowish liquid
2 pH 7.0 -7.6
3 Protein (mg/ml) Not less than 5.0 mg/ml
4 No additional band other than principal band
SDS PAGE
observed
5 Identified with specific antibody and resembles
Immunoblotting
with qualified standard
6 Bioactivity (U/mg) 160 U/mg to 240 U/mg
7 Monomer (%) More than 95%
8 Single Chain Content (%) More than 60 %
9 HCP (ppm) Less than 100 ppm
10 Sialic Acid (mol/mol of
2.9 to 5.7 moles/mol of TNK-tPA
TPA)
1 1 Neutral Sugar (mol/mol of
10.5 to 13.5 moles/mol of TNK-tPA
TPA)
12 Type-I 28-40 %,
Type I , Type II content
Type-II 60-72%
13 HCD Less than lOng/dose
14 BET < lEU/mg
15 Serine(S )-Tyrosine(Y)-Glutamine(Q) -
Valine(V)-Isoleucine(I)-Cysteine(C)-Arginine(
N-Terminal Sequence (First
R)-Aspartic acid(D) -Glutamic acid(E)-
15 amino acid )
Lysine(K)_Threonine(T)-Glutamine(Q)-
Methionine(M)-Isoleucine(I)-Tyrosine(Y)
16 Osmolality 260-320 mOsm/Kg
17 Arginine Content 50-60 mg/ml
18 Chromatogram pattern resembles with qualified
Peptide mapping
standard
19 UV Spectrum (Amax ) 280+2nm
In an embodiment the process of the present invention is capable to remove or inactivate
viruses as potential adventitious agents as assessed using a scaled down purification process.
The high log clearance values obtained for XMuLV, PRV, Reo-3 , and MMV provides a
very good assurance that any adventitious viruses which could not be detected, or might gain
access to the production process, would be cleared/or inactivated, during highly capable
purification process, mentioned in the current invention and thus reducing the overall risk to
patient safety.
In addition to higher assurance of viral safety, the aforementioned improvements in the
purification process of TNK-tPA are also beneficial in terms of decreased human
intervention, lower capital and operational expenditures for higher yield TNK-tPA
preparation.
In an embodiment the present invention provides a pharmaceutical composition comprising
the TNK-tPA retentate obtained from the process of present invention in liquid parenteral I.V
formulation with pharmaceutically acceptable excipients for acute myocardial infarction and
acute ischemic stroke.
In an embodiment the pharmaceutical composition of present invention comprises:
In another embodiment the present invention provides the use of the isolated and prepared
TNK-tPA in liquid parenteral I.V formulation for acute myocardial infarction and acute
ischemic stroke.
The invention is described in detail herein below with respect to the following examples
which are provided merely for illustration and are not intended to restrict scope of invention
in any manner. Any embodiments that may be apparent to a person skilled in the art are
deemed to fall within the scope of present invention.
Example- 1
The cell free harvest containing TNK-tPA is subjected to Affinity chromatography column
packed with Blue Sepharose FF. before loading, the Column is equilibrated with 5 Column
Volume (CV) of equilibration buffer. The loading is stopped till column achieve saturation.
The loading capacity of column is decided based on the Dynamic Binding Capacity (DBC) of
column which is in range of 1 - 2 mg/ml. After loading, column is washed with equilibration
buffer until loosely bound process and product related impurities were washed away in
equilibration wash. For further removal of host cell proteins another wash buffer is used
which is composed of urea, sodium chloride, sodium phosphate and polysorbate 20.
After column wash, TNK-tPA is eluted using elution buffer containing 20-50 mM Sodium
Phosphate, 1-2 M NaCl, 2-3 M urea, and 0.04-0.1 % polysorbate 20. Affinity-I eluate is
filtered with 0.2mih filter. Samples are withdrawn and analysed by reduced and non reduced
SDS PAGE to know the purity profile and single chain/double chain content. Those who
skilled in art can understand the criticality of single chain/double chain composition in final
TNK-tPA drug substance.
The present invention is advantageous due to direct capture of clarified harvest without
mixing in large mixing tanks.
Example- 2
Affinity-I Chromatography Eluate is diluted with affinity-II dilution or affinity
chromatography equilibration buffer containing 20-50 mM Sodium Phosphate, 0.04-0.1 %
polysorbate20 at pH 7.2 to reduce the conductivity up to less than 15 ms/cm. Diluted sample
is clarified using 0.2 m filter and loaded on to Affinity-II chromatography. Column is washed
with equilibration buffer to bring the UV280 absorbance to baseline. Column is further
washed to remove process and product related impurities with wash buffer containing 20-50
mM sodium phosphate, 1-3 M NaCl, 0.04-0.1% polysorbate 20 and pH 7.2.Purified TNKtPA
is recovered and eluted from the column by passing elution buffer consisting of 5-25 mM
sodium acetate, 1-4 M urea, 0.1-0.4 M EACA and pH 4.0-5.0. All the chromatography
samples including load, flow through, washes, and elution were analyzed using following
analytical methods:
SDS PAGE (reduced/non reduced) for purity and single chain/double chain content.
Size Exclusion High Performance Chromatography (SEC-HPLC) For Aggregate Content
TNK -tPA content measured by Clot Lysis assay.
Total Protein by Bradford and UV280 nm.
HCP content using ELISA (Cygnus third generation kit)
Affinity chromatography is optimized for removing process & product related impurities. The
method of elution in this step is optimized in such a way that it complements to viral
inactivation step and the composition with condition of elution buffer e.g. urea, EACA, and
low pH are optimized to inline with viral inactivation. Approximately 2 to4 log reduction of
viral clearance and 1.0 to 1.5 log reduction of host cell proteins (HCP) are achieved after
Affinity-II chromatography step.
The other advantage is using EACA at acidic pH in Affinity Chromatography-II in elution
buffer inspite of L-Arginine and EACA at neutral pH. This particular change in purification
step is valuable in reducing the cost of L-Arginine and also provides an optimum condition
for viral inactivation. Hence, it can be stated that the same step is not only favorable for
TNK-tPA elution but also optimum for viral inactivation that in turn reduces the work load
and material consumption with time.
Example- 3
The Elution of Affinity Chromatography is subjected to low pH and chemical inactivation
using sodium caprylate. Mixture is incubated at 20 to 25°C for 60 min. In viral inactivation
step, sodium caprylate used is in very low amount that eliminates the need of large mixing
vessels. In prior art sodium caprylate was used to inactivate viruses present in before capture
chromatography where volumes are comparatively higher hence quantity of sodium caprylate
required was also high. In present invention, sodium Caprylate is added after second
chromatography steps where volume to be handled is low and therefore requires less amount
of sodium caprylate and much smaller vessel for handling. Apart from that, the use of sodium
caprylate at pH 4.5 as compared to neutral or alkaline pH, provides a more effective and
robust viral inactivation in the process.
After viral inactivation the solution is diluted using phosphate buffer for loading on to
Affinity chromatography (mixed mode chromatography) to remove traces of impurities,
specifically HCD, HCP and viral impurities if any. Approximately 2-4 log reduction of viral
clearance and 0.5 - 1 log reduction of HCP clearance are achieved by affinity
chromatography. In prior art same ceramic hydroxyl apatite is described for tissue
plasminogen activator purification, but none of the process have described the capability to
remove impurities e.g. HCP, DNA and viruses. Criticality of removing such impurities is
evident by the fact that the amount of these impurities is tested in final product (except viral
load) and is part of final drug substance release specifications. All the chromatography
samples including load, flow through, washes, and elution are analyzed using following
analytical methods:
SDS PAGE (reduced/non reduced) for purity and single chain/double chain content.
Size Exclusion High performance Chromatography (SEC-HPLC) for aggregate content
TNK -tPA content measured by Clot Lysis assay.
Total Protein by Bradford and UV280 nm.
HCP content using ELISA (Cygnus third generation kit)
Example- 4
The Affinity chromatography eluate without any conditioning is directly loaded on to cation
exchange chromatography for concentration and buffer exchange of target protein. Cation
exchange chromatography is optimized in such a way that it avoids cumbersome dilution
steps for feed conditioning and therefore the affinity-Ill eluate can be directly loaded on to
the cation exchange chromatography. TNK-tPA is recovered from the column by passing
elution buffer containing 55 mg/ml L-Arginine, 17 mg/ml of orthophosphoric acid, 0.43
mg/ml Polysorbate 20 and pH 7.4.Cation exchange chromatography eluate is subjected to
filtration for viral reduction and the resultant filtrate is further concentrated using Tangential
Flow Filtration (TFF) system to achieve the final drug substance concentration. After
concentration the TFF Retentate is sterile filtered and kept at -20°C for further use. Drug
substance produced by the purification process of present invention is thoroughly analyzed by
the state of art and validated analytical procedures which includes but not limited to; Identity
and purity check by SDS PAGE, Western Blot, N-terminal sequence analysis and peptide
map,
HCP determination using ELISA,
Bioactivity and TNK-tPA quantification using clot lysis assay,
Host cell DNA quantification using qPCR,
Endotoxin quantification using LAL test,
Aggregate and single chain/double chain content using size exclusion HPLC,
Arginine content & Osmolality,
Sialic acid, neutral sugars, type-I and type-II glycoforms analysis,
Analysis of process related impurities e.g. Gentamycin, MTX, Urea, Sodium Caprylate, and
EACA using in-house developed methods.
After extensive analysis and biophysical comparison with innovator product it can be
concluded that the product purified by the process described in current invention is yielding
TNK-tPA product which is highly similar to innovator product with overall process yield of
more than 60%.
Example 5 :
A Periodic counter current chromatography (PCC) for affinity-I step has been performed with
cell culture supernatant containing TNK-tPA from perfusion based bioreactor. In batch mode
dynamic binding capacity for affinity-I chromatography media were evaluated and based on
the information obtained from break through analysis a three column PCC has been
experimented on XK16- 5 ml BLUE SEPAHROSE FF. The chromatographic buffer
compositions were kept same as mentioned in Example- 1.
Example 6 :
The method for preparation of a liquid mixture of controlled pH & ionic strength for required
buffers, dilution and/or conditioning of chromatography load by five pump based customized
AKTA process system with a maximum flow rate of 600 L/h for TNK-tPA downstream
processing. The liquid mixtures prepared with the above system with defined recipes are
suitable for purification of TNK-tPA at different chromatography stages as mentioned in
Example- 1 to 4.

WE CLAIM:
1. A process for isolation and purification of TNK-tPA comprising steps of:
(i) subjecting cell free harvest obtained from CHO cell culture to affinity
chromatography to capture TNK-tPA and obtaining an eluate containing partially purified
TNK-tPA.
(ii) subjecting the eluate of step (i) to affinity chromatography for additional
purification of TNK-tPA and obtain an eluate containing primarily TNK-tPA.
(iii) viral inactivation of eluate of step (ii) to obtain the viral inactivated sample;
(iv) subjecting the viral inactivated sample of step (iii) to a further affinity
chromatography-III for additional purification to obtain an eluate containing primarily
highly purified TNK-tPA;
(v) subjecting the eluate of step (iv) to cation exchange chromatography to obtain an
eluate containing highly purified preparation of TNK-tPA;
(vi) subjecting the eluate of step (v) to virus reduction filtration for removal of virus
present;
(vii) concentrating the sample of step (vi) to obtain TNK- tPA; wherein the yield of the
process is more than 60 % and purity of TNK-tPA obtained is more than 95% as
measured by Size exclusion chromatography.
2. The process as claimed in claim 1, wherein the TNK-tPA purity is more than 95% by
Size Exclusion Chromatography and wherein the other critical quality attributes are:
No additional band other than principal
SDS PAGE
band observed
Monomer (%) More than 95%
Single Chain Content (%) More than 60 %
HCP (ppm) Less than 100
HCD (ng/dose) Less than 10
3. The process as claimed in step (i) of claim 1, wherein the affinity chromatography
comprises a stationary phase and a mobile phase;
wherein the stationary phase is selected from the group comprising Blue Sepharose 6 Fast
Flow, Lysine Hyper D and Ceramic Hydroxy Apatite (CHT), preferably the stationary
phase is Blue Sepharose 6 FF;
wherein the mobile phase is selected from the group comprising sodium phosphate
buffer, sodium chloride and urea, or a mixture, preferably a mixture;
wherein the sodium phosphate is present in range from 20-50 mM, preferably in range
from 20-40mM, sodium chloride is present in range from 1-2.5 M, preferably in range
from 1.5 - 2 M and urea is present in range from 1-4 M, preferably in range from 2-3 M;
wherein the pH of the mobile phase is present in range from 7-8, preferably in a range of
7-7.6, more preferably in range of 7.2-7.4.
4. The process as claimed in claim 3, wherein the affinity chromatography provides 0.8 -
1.5 log reduction in host cell proteins (HCP).
5. The process as claimed in step (ii) of claim 1, wherein the affinity chromatography
comprises comprises a stationary phase and a mobile phase;
wherein the stationary phase is selected from the group comprising Blue Sepharose 6 fast
flow, Lysine Hyper D and Ceramic Hydroxy Apatite (CHT), preferably the stationary
phase is Lysine Hyper D ;
wherein the mobile phase is selected from the group comprising sodium acetate buffer,
urea and epsilon aminocarproic acid (EACA), or a mixture, preferably a mixture;
wherein the sodium acetate is present in range from 5-25 mM, preferably in range from
5-15 mM, urea is present in range from 1-4 M, preferably in range from 2-3 M and
EACA is present in range from 0.1-0.4 mM, preferably in range from 0.1-0.2 mM;
wherein the pH of the affinity chromatography mobile phase is in range of pH 3.5-6,
preferably in range of 4-5, more preferably in range of 4.5-5.
6. The process as claimed in claim 5, wherein the affinity chromatography results 1- 1.5 log
reduction in host cell proteins (HCP) and 1 - 4 log reduction of viral clearance.
7. The process as claimed in claim 5, wherein the affinity chromatography results more
than 1.5 log reduction with XMuLV and more than 4 log reduction with PRV.
8. The process as claimed in step (iii) of claim 1, wherein viral inactivation is conducted by
low pH and chemical inactivation;
wherein chemical inactivation is done by treating the sample with chemical selected from
the group comprising sodium cholate, triton, Beta-propiolactone, tri(n-butyl)phosphate
(TNBP), and sodium caprylate, preferably sodium caprylate in the presence of urea;
wherein sodium caprylate is present in the range from 0.001% to 0.10% w/v, preferably
0.01% - 0.07% (w/v), more preferably in the range of 0.05%;
wherein concentration of urea is present in the range of 1-4 M, preferably 2-3 M;
wherein viral inactivation is conducted by holding the sample for a period from 40-180
minutes, more preferably for a period from 40-80 minutes;
wherein holding of the sample at a temperature range from 15-45°C, more preferably in
the range from 20-30°C;
wherein the pH is present in range from 4.0 to 4.7, more preferably in the range from 4.3
to 4.7.
9. The process as claimed in claim 8, wherein the Low pH and chemical inactivation results
in more than 5 log reduction with XMuLV and PRV.
10. The process as claimed in step (iv) of claim 1, wherein the affinity chromatography
comprises a stationary phase and a mobile phase;
wherein stationary phase is selected from the group comprising Blue Sepharose 6 fast
flow, Lysine Hyper D and Ceramic Hydroxy Apatite (CHT), preferably the stationary
phase is Ceramic Hydroxy Apatite (CHT) ;
wherein the mobile phase is selected from the group comprising phosphate buffer, 2-(NMorpholino)
ethanesulfonic acid hydrate (MES- Hydrate), sodium chloride and urea or a
mixture, preferably a mixture;
wherein the phosphate buffer is present in range from 5-50 mM, preferably in range from
5-15 mM, MES- Hydrate is present in range from 2-20 mM, urea is present in range from
1-4 M, preferably in range from 1-3 M and sodium chloride is present in range from 0.1-
1.0 M, preferably in range from 0 1 to 0.5 M.
wherein the mobile phase pH is in the range from 6 - 9;
wherein the affinity chromatography elution type may be linear, step or in combination of
both, preferably the elution used is linear salt gradient;
wherein the salt of this elution may be selected from group comprising potassium
chloride, sodium chloride, sodium phosphate and ammonium sulphate, preferably the salt
is sodium chloride and concentration of sodium chloride is in a range from 0.1-1.0 M
sodium chloride.
11. The process as claimed in claim 10, wherein the affinity chromatography results 0.5- 1
log reduction in host cell proteins (HCP) and 2 - 4 log of viral clearance.
12. The process as claimed in claim 10, wherein the affinity chromatography results more
than 4 log reduction with XMuLV and PRV and more than 3 log reduction with MMV
and Reo 3 viruses.
13. The process as claimed in step (v) of claim 1, wherein cation exchange chromatography
comprises a stationary phase and a mobile phase;
wherein stationary phase is selected from the group comprising Fractogel S0 3, Fratogel
SE Hicap, SP Sepharose FF, CM Sepharose FF, preferably the stationary phase is
Fractogel SO3;
wherein the mobile phase is selected from the group comprising L-Arginine, Ophosphoric
acid and polysorbate-20 or a mixture, preferably a mixture;
wherein the L-Arginine is present in range from 10-350 mM, preferably in range from
250-350 mM, O-phosphoric acid is present in range from 0.5-1%, preferably in range
from 0.6%-0.8% and polysorbate-20 is present in range from 0.01-0.05%, preferably in a
range from 0.04 to 0.05 % ;
wherein the mobile phase pH is in range from 7.0 to 7.5, preferably in the range 7.3- 7.5.
14. The process as claimed in claim 13, wherein the cation exchange chromatography results
more than 1 log viral clearance with MMV and more than 0.5 log clearance for host cell
proteins (HCP).
15. The process as claimed in step (vi) of claim 1, wherein virus filtration is carried out for
eluate obtained from cation exchange chromatography by nanofilter; wherein the
nanofilter is PES; wherein the size of nanofilter is in a range from 15-20 nm.
16. The process as claimed in claim 15, wherein the virus filtration results more than 4 log
reduction of XMuLV, more than 3 log reduction of PRV, more than 4 log reduction of
Reo-3 and more than 4.5 log reduction of MMV.
17. The process as claimed in step (vii) of claim 1, wherein filtration is performed to
concentrate the sample by a filtration method selected from the group comprising
microfiltration, ultrafiltration, nanofiltration, macrofiltration and tangential flow
filtration, preferably the filtration method is tangential flow filtration;
wherein the filter is ultra filtration membrane;
wherein the ultra filtration membrane is PES;
wherein the size of ultra filtration membrane is in a range from 5-30 kDa, preferably the
size of ultra filtration membrane is 10 kDa.
18. The process as claimed in claim 17, wherein the concentrate is TNK-tPA retentate.
19. A process as claimed in claim 1, wherein periodic counter current chromatography is
used for Affinity-I chromatography
20. A process as claimed in claim 1, wherein Inline conditioning approach is used for buffer
and load preparation for Affinity-I, Affinity-II, Affinity-Ill (MMC) and IEC
chromatography.
21. Use of the isolated and prepared TNK-tPA as claimed in claim 1, in liquid parenteral I.V
formulation for acute myocardial infarction and acute ischemic stroke.
22. A pharmaceutical composition comprising the TNK-tPA obtained as claimed in claim 1
along with pharmaceutically acceptable excipients.
23. The pharmaceutical composition as claimed in claim 20, comprises :