Pfizer v. Genentech
`IPR201(cid:26)-01488
`Genentech Exhibit 202(cid:23)
`
`

`

`4182
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`Immunology: Gorman et al.
`
`Proc. Natl. Acad. Sci. USA 88 (I991)
`
`were CDR-grafted (9) into the 1.5-kb HindIII fragment from
`pNH3l6 encoding the Campath-IH antibody heavy chain by
`in vitro mutagenesis with three oligonucleotides.
`The KOL-based reshaped VH region was created by in
`vitro mutagenesis of a Campath-9 antibody VH region cDNA
`clone in M13-VHPCR1 with five oligonucleotides that were
`designed to mutate the Campath-9 VH region framework
`residues into the corresponding residues of the KOL anti-
`body (18). These five mutagenic oligonucleotides were si-
`multaneously introduced in a single mutagenesis reaction.
`Twelve clones were sequenced and each clone had incorpo-
`rated the five mutagenic oligonucleotides. The plasmid
`pVHKOL/Cm encoding the KOL-based reshaped heavy
`chain consists of the following adjacently ligated fragments:
`the 9.8-kb vector pHBAPr—l-gpt (14) linearized at its cloning
`site with HindIII and BamHI containing the B-actin pro-
`moter, xanthine-guanine phosphoribosyltransferase, and am-
`picillin-resistance genes; the 39-bp HindIII—Nco I linker; a
`698-bp Nco I—BamHI fragment encoding the KOL-based
`reshaped VH region; a 2.3-kb BamHI—Sph I fragment con-
`taining a human C51 region gene (15); and the 20-bp Sph I—Bgl
`II synthetic linker.
`The plasmid pVLREI/CK encoding the reshaped light chain
`is identical to the plasmid pLD9 (16) except that the three
`CDRs of the Campath—9 antibody VL region were CDR-
`grafted (9) into the 748-bp HindIII fragment from pLD9
`encoding the Campath-IH antibody light chain by in vitro
`mutagenesis with three oligonucleotides.
`Transfections and Antibody Purification. The CD4-
`expressing cell line HCD4-NB2 is a clone of the rat T-cell line
`NB2-6TG stably transfected by electroporation with the
`expression vector pSFSVneo (19) containing cDNA encod-
`ing the human CD4 antigen (20).
`Plasmids encoding antibody chains were cotransfected as
`described (21) into dihydrofolate reductase-deficient Chinese
`hamster ovary cells (106 cells per 75-cm2 flask) using 9 pg and
`1 pg of the appropriate heavy and light chain constructs,
`respectively. Transfectants were selected in medium con-
`taining 5% dialyzed fetal bovine serum for 2—3 weeks, and
`antibody-secreting clones were identified by ELISA of cul-
`ture supematants. Chimeric and reshaped antibodies were
`purified from culture supematants using protein A-Sepharose
`CL-4B (Pharmacia) column chromatography as described
`(22). Antibody concentrations were determined by absor-
`bance at 280 nm.
`Immunofluorescence and Flow Cytometry. HCD4-NB2
`cells were washed with staining medium (phosphate-buffered
`saline containing 0.1% bovine serum albumin, 1% heat-
`inactivated normal rabbit serum, and 0.1% sodium azide) and
`then incubated with either the chimeric or reshaped antibod-
`ies (105 cells per 0.1 ml) diluted in staining medium for 1 hr
`at 4°C. The cells were washed and then incubated with
`fluorescein isothiocyanate-conjugated anti-human IgGl (y-
`chain-specific) antibodies (The Binding Site, Birmingham,
`U.K.) diluted 1:30 in staining medium for 1 hr at 4°C.
`Propidium iodide (100 yg/ml final concentration) was added
`during the last 10 min of incubation. Cells were thoroughly
`washed and resuspended in 0.5 ml of staining medium. Mean
`cellular fluorescence (3000 live cells per sample) was deter-
`mined with a Cytofluorograph (model 50-H Ortho Instru-
`ments). Propidiumiodide-stained dead cells were gated-out.
`Fifty percent antigen binding titers were determined by fitting
`the data to a sigmoid curve by a least squares iterative
`procedure (23).
`Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC).
`Antibodies were assayed by ADCC with activated human
`peripheral blood mononuclear cells (24). Briefly, 5 x 10“
`HCD4-NBZ cells were labeled with ”Cr and incubated for 1
`hr at room temperature with different concentrations of
`antibodies. A 75-fold excess of activated cells was added as
`
`effectors. After 4 hr at 37°C, cell death was determined by
`measuring ”Cr release.
`
`RESULTS
`
`Cloning of V1, and V“ Region cDNA. cDNAs encoding the
`VL and VB regions from the Campath-9 antibody-secreting
`clone YNB46.1.8SGZB1.19 (10) were isolated by PCR using
`primers that amplify the segment of cDNA encoding the
`amino-terminal region through the joining region (11). VL
`region clones were first screened by hybridization with a
`32P-labeled oligonucleotide probe complementary to CDR 2
`of the light chain expressed by the rat Y3-Ag1.2.3 myeloma
`cell line (12) that was used as the fusion partner to generate
`the Campath-9 antibody-secreting hybridoma. Subsequent
`nucleotide sequence analysis was restricted to clones that did
`not contain sequence complementary to this probe (about 5%
`of clones). In this manner, two cDNA clones from indepen-
`dent PCR amplifications were identified that encoded iden-
`tical VL regions. Nucleotide sequence analysis of random VH
`region clones from two independent PCR amplifications
`revealed a single species of Va region cDNA. These cDNA
`sequences have been submitted to the GenBank data base,
`and their predicted amino acid sequences are shown (Fig. 1).
`As no additional VL or V" region-encoding clones were
`identified, it was assumed that these sequences were derived
`from the Campath-9 antibody genes.
`Chimeric Antibody Constructs. Plasmids were constructed
`that encoded a rat/human chimeric version of the Campath-9
`antibody. The plasmid meat/Cal encodes a chimeric heavy
`chain consisting of the Campath-9 VH region (Fig. 1A) and a
`human C61 region. The plasmid pVLrat/C,‘ encodes a chi-
`meric light chain consisting of the Campath-9 VL region (Fig.
`18) and a human CK. These chimeric heavy and light chains
`were coexpressed in Chinese hamster ovary cells to produce
`a chimeric antibody.
`Reshaped Antibody Heavy Chain Constructs. Possibly the
`largest unknown variable when reshaping an antibody is the
`selection of the human immunoglobulin V region from which
`the framework sequences are derived. Because the frame-
`work regions hold the CDRs in their correct spatial orienta-
`tion and can sometimes even participate in antigen binding
`(29), this selection could be important. At present, there are
`insufficient published reshaping results to generalize a “best
`framewor ” selection strategy. Reshaping experiments to
`date (9, 30-32) have not compared the effectiveness of
`different human frameworks incorporating the same rodent
`CDRs.
`To investigate the importance of framework selection and
`to maximize our chances of producing a functional reshaped
`CD4 antibody, we have designed two different versions of
`reshaped VH regions. In the first case, we designed a re-
`shaped VH region that derives its CDRs from the Campath-9
`VH region and its framework sequences from the NEW-based
`framework that had been used previously for the reshaped
`antibody Campath-lH (9) and others (30, 31). Given the
`demonstrable antigen binding of these antibodies, it was
`reasonable to try the same framework sequences as well. A
`plasmid was thus constructed, pVHNEW/CGI, that encodes
`a reshaped heavy chain consisting of an NEW-based VH
`region with Campath-9 VH region CDRs (Fig. 1A) and a
`human C51 region.
`In the second case, we designed a reshaped VH region that
`derives its CDRs from the Campath-9 V3 region and its
`framework sequences from the VH region of the human
`myeloma protein KOL (18). The VH region of KOL was
`chosen because of all known human heavy chain V regions its
`overall amino acid sequence is very homologous to the
`Campath-9 VH region (Fig. 1A) containing 72% identical
`residues (excluding gaps introduced for alignment purposes).
`
`

`

`Immunology: Gorman et al.
`
`Proc. Natl. Acad. Sci. USA 88 (1991)
`
`4183
`
`A
`
`CAHPATH-9
`NEW
`CAMPATH-1H
`NEW—based resh.
`KOL
`KOL-based resh.
`
`CAMPATH-9
`NEW
`CAMPATH—tH
`NEW-based resh.
`KOL
`KOL—based resh.
`
`B
`
`CAMPATH-Q
`REI
`CAMPATH—1H
`RBI-based resh.
`
`CAMPATH—9
`REI
`CAMPATH-iH
`RBI-based resh.
`
`70
`60
`50
`40
`30
`20
`10
`QVQLQESGGG LVQPGRSLKL SCAASGLTFS NYGHAHVRQA PTKGLEWVAT ISHDGSD--T YFRDSVKGRF
`....EQ..P.
`..R.SQT.S. T.TV..S...
`.DYYT....P .GR....IGY VFYH.TSDD.
`---TPLRS.V
`........P. ..R.SQT.S. T.TV..F..T DPY.N....P .GR....IGF .RDKAKGYT. EYNP ..... V
`........P.
`..R.SQT.S. T.TV..F..T ......... P .GR....IG. ....... --. ......... V
`....V ..... V ....... R.
`..SS..FI.. S.A.Y..
`.G..
`I .WD..
`Q—- HYA .......
`....V ..... V ....... R.
`..SS..FI ............. G ............... —-
`..........
`
`129
`120
`110
`100
`90
`80
`TISRDNGKST LYLQHDSLRS EDTATYYCAR QG———————— TIAG-IRHWG QGTTVTVSS
`.MLV.TS.NQ PS.RLS.VTA A...V ..... N--------- L...C.DV..
`..SL .....
`.HLV.TS.NQ FS.RLS.VTA A...V ..... E.H------- -T.APFDY..
`..SL .....
`.MLV.TS.NQ FS.RLS.VTA A...V ................... - ....... SL .....
`......S.N.
`.F.......P ...GV.F
`D.GHGFCSSA SCF.P—DY ..... P .....
`......S.N.
`.F.......P ...GV.F
`------------ - ..............
`
`70
`60
`50
`A0
`30
`20
`10
`DIQLTQSPVS LSASLGETVN IECLASEDIY SDLAWYQQKP GKSPQLLIYN TDTLQNGVPS RFSGSGSGTQ
`...M....S.
`....V.DR.T .T.Q..Q..I KY.N....T.
`..A.K....E ASN..A ............. D
`...M....S.
`....V.DR.T .T.K..QN.D KY.N......
`..A.K.....
`.NN..T ............. D
`...M....S.
`....V.DR.T .T .................... A.K ........................ D
`
`
`100
`90
`80
`107
`YSLKINSLQS EDVATYFCQQ YNNYPWTFGG GTKLEIK
`.TFT.S...P ..I...Y...
`.QSL.Y...Q ....Q.T
`FTFT.S...P ..I...Y.L. HISR.R...Q ...V...
`FTFT.S...P ..I...Y ......... .........QV
`
`Fro. 1.
`Comparison of the amino acid sequences of the heavy (A) and light (B) chain V regions described in the text. Dots indicate residues
`that are identical to the corresponding residue in Campath-9. Hyphens represent spaces introduced in the sequences by GAP (25) to aid the
`alignment. CDRs of Campath-9 are underlined and residues encoded within the amplification primers and cloning vectors are overlined. resh.,
`Reshaped. Sequences of NEW, KOL, and REI are from the Swiss-Pro! protein sequence data base, release 14. It should be noted that there
`are some minor sequence differences of NEW and KOL as recorded in the various data bases—for example, Swiss-Prot and Brookhaven (26).
`The actual framework sequences of the NEW- and REI-based reshaped V regions described here are identical to those of the Campath-IH
`antibody (9), which differ only slightly from the reported framework sequences of NEW (27) and REI (28). For consistency, and given the
`demonstrable antigen binding of this reshaped antibody, identical framework sequences were used here.
`
`This was determined by a computer search of several data
`bases. By contrast, the NEW VH region sequence has only
`47% identical residues. We reasoned that since the primary
`function of the framework sequence is to hold the CDRs in
`their correct spatial orientation, we could maximize the
`chances of retaining correct CDR structure (and hence anti-
`gen affinity) by deriving framework sequences from a human
`VH region that is most homologous to that of the rodent. Of
`the several homologous human VH regions available, the
`choice of KOL was made because its three-dimensional
`structure is well characterized. A plasmid was thus con-
`structed, pVHKOL/Cm,
`that encodes a reshaped heavy
`chain consisting of a KOL-based VH region with Campath-9
`VH region CDRs (Fig. 1A) and a human C01 region.
`Reshaped Antibody Light Chain Construct. We have de-
`signed a reshaped VL region that derives its CDRs from the
`Campath-9 VL region and its framework sequences from the
`RBI-based framework that has been used previously for the
`reshaped antibody Campath-lH (9). Again, given the demon-
`strable antigen binding of this antibody, it was reasonable to
`try the same framework as well. A plasmid was constructed,
`pVLREI/CK, that encodes a reshaped light chain consisting of
`an RBI-based VL region with Campath-9 VL region CDRs
`(Fig. 13) and a human CK region. A second reshaped VL
`version was not created as with the reshaped VH region
`because REI is already highly homologous (67% identical
`residues) to the rat VL region of Campath-9. Thus this
`reshaped light chain was coexpressed with the reshaped
`heavy chains in Chinese hamster ovary cells to produce two
`reshaped antibodies (KOL- and NEW-based) differing only
`in their human-derived VH region framework sequences.
`
`Properties of Chimeric and Reshaped Antibodies. The abil-
`ities of the chimeric and reshaped antibodies to bind the
`CD4+ cell line HCD4-NBZ were compared by immunofluo-
`rescence staining (Fig. 2). The chimeric and KOL-based
`reshaped antibodies stained CD4+ cells well. The titration
`curves of these two antibodies were fitted to a sigmoid curve,
`and the concentrations (mean 1‘ SEM) of chimeric and
`KOL-based reshaped antibodies needed to achieve 50%
`antigen saturation were determined to be 2.21 t 0.16 and 7.16
`t 0.45 pg/ml, respectively. Thus the avidity of the KOL-
`based reshaped antibody is only slightly reduced as it only
`
`
`
`Meanfluorescence
`
`800
`700
`600
`500
`400
`300
`200
`
`100
`
`Antibody concentration, pg/ml
`FIG. 2. Fluorescence of CD4+ cells stained with chimeric and
`reshaped antibodies. 0, Campath-9 chimeric antibody; 0, KOL-
`based reshaped antibody; A, NEW-based reshaped antibody; A,
`Campath-lH antibody (isotype-matched negative control). The
`KOL— and NEW-based reshaped antibodies have the same REI-
`based reshaped light chain.
`
`

`

`4184
`
`Immunology: Gorman et a].
`
`Proc. Natl. Acad. Sci. USA 88 (I991)
`
`NO
`
`
`
`Percentlysis
`
`.a (II
`
`o-5
`
`Antibody concentration, ,ug/ml
`
`FIG. 3. ADCC with chimeric and reshaped antibodies. Symbols
`are the same as in Fig. 2.
`
`takes three times the amount of this antibody to give the same
`50% binding as the chimeric antibody. All KOL VH region
`framework residues were incorporated into this reshaped VH
`region except for the proline at position 124 (Fig. 1A), which
`was kept as threonine. A second version that incorporates
`this proline residue gave similar results (not shown). By
`contrast, the NEW-based reshaped antibody stained CD4+
`cells only poorly even at the higher concentrations. The
`control Campath-IH antibody did not stain cells at any
`concentration. Also, the chimeric and KOL-based reshaped
`antibodies were effective in cell-mediated lysis, whereas the
`NEW-based reshaped and control Campath-lH antibodies
`were ineffective (Fig. 3).
`
`DISCUSSION
`
`We have described here the successful reshaping of the CD4
`antibody Campath—9. This result, together with the previ-
`ously described reshaping of other therapeutic antibodies (9,
`32), demonstrates the feasibility of applying this concept to
`the many rodent-derived monoclonal antibodies with clinical
`potential. The Campath-lH antibody has already been used
`successfully in clinical studies of lymphoma therapy (33) and
`in the treatment of an autoimmune disorder (10). In this later
`case,
`the Campath-lH antibody was combined with the
`Campath-9 antibody to give a long-term remission in a case
`of systemic vasculitis that appeared intractable prior to
`Campath-9 antibody treatment. Although the relative contri-
`butions and importance of the Campath-lH and Campath-9
`antibodies cannot be ascertained from this single case study,
`the availability of Campath-9 as a reshaped antibody, Cam-
`path-9I-I (the KOL-based version), should provide for further
`useful clinical studies.
`Our reshaping of Campath-9 into Campath—9H raises in-
`teresting questions regarding general strategies for the re-
`shaping of rodent antibodies. At present, there are only four
`additional reports of reshaped antibodies and in no case has
`the effectiveness of two different human antibody frame-
`works regions been compared (9, 30—32). Three of these
`antibodies had reshaped VH regions based on NEW (9, 30,
`31), two of which had reshaped VL regions based on RBI (9,
`31), regardless of whether closer homologies existed in the
`sequence data bases. In the fourth example, the antibody was
`reshaped based on a homologous human framework, but 12
`of the 29 residues that differed between the human and mouse
`VH region frameworks were left as in the mouse sequence,
`and no data were presented that compared this reshaped
`antibody with a form in which all of the framework residues
`were derived from the human sequence (32). For the reshap-
`ing of Campath-9, we have shown that the selection of a
`particular human framework can be important in the reten-
`tion of antibody avidity. We have made two reshaped anti-
`bodies that differ only in their usage of human VH region
`
`framework sequences, KOL and NEW, and found one form
`to be far superior to the other. The KOL-based CD4 antibody
`retained biological activity in ADCC assays and had a relative
`binding avidity only slightly reduced from the unaltered V
`region sequences of the chimeric CD4 antibody. In contrast,
`the NEW-based CD4 antibody, though still retaining speci-
`ficity for CD4, had a considerably reduced relative binding
`avidity and had no biological activity. The KOL VH region
`has a 72% homology to Campath—9 VH region, whereas the
`NEW VH framework has only 47% homology. In this case
`then, it would seem that the selection of a human V region
`framework that was highly homologous to the rodent V
`region was the best strategy for framework selection. We
`have also successfully reshaped a CD3 antibody by the same
`approach (E.G.R., unpublished data), so this strategy may
`prove to be generally applicable to antibody reshaping.
`Arguably, although such a bestfit strategy has been applied
`here to whole antibody V regions, it might also be applied
`separately to individual variable, diversity, and joining re-
`combining segments of an antibody V region.
`The different avidities we observe when reshaping with
`KOL- and NEW-based frameworks are likely to be due to the
`complex intrachain associations between CDR and frame-
`work residues. Alternatively, difl'erent interchain V region
`associations between these two heavy chains and the RBI-
`based reshaped light chain may also play a role. One possible
`structural explanation for the differences between the KOL-
`and NEW-based reshaped antibodies is described by Tra-
`montano et al. (34). In studies of a series of solved immu-
`noglobulin structures they observed that the conformation of
`the heavy chain CDR 2, “H2 loop,” is dependent upon the
`length and sequence of this loop and its interaction with the
`framework residue at position 71 (Kabat numbering system).
`KOL and NEW have distinctly different structures in this
`region and a different residue at position 71. The H2 loop of
`the Campath-9 antibody is very similar to that of KOL and
`both contain an arginine residue at the relevant framework
`position (this is position 74 in Fig. 1A). Perhaps the change of
`this residue upon reshaping to the NEW-based framework
`accounts in part for its low avidity. However, it should be
`noted that Campath-lH was successfully reshaped to the
`NEW-based framework despite having a substantially differ-
`ent H2 loop length and sequence and also a different frame-
`work residue at position 71 (34). Clearly the ability to use
`structural features like this to reliably predict a suitable
`strategy for reshaping will benefit from more examples where
`different strategies are experimentally compared.
`In previous studies, genes encoding reshaped antibodies
`were produced either by total synthesis of the desired se-
`quence (32) or by in vitro mutagenesis of a human V region
`sequence to incorporate the rodent CDRs (9, 30, 31). We
`propose the following strategy based on our successful re-
`shaping experiments whereby the isolated rodent V region is
`used as a starting point for constructing reshaped V regions.
`Here, human framework sequences are transferred to the
`rodent V regions by means of in vitro mutagenesis. When
`coupled with the bestfit method from above, mutagenic
`oligonucleotides can be highly homologous to the rodent
`frameworks, and hence the efficiency of mutagenesis is high.
`In the case of Campath-9H, this was accomplished in a single
`mutagenesis reaction with five oligonucleotides 33—58 bases
`in length. This strategy should be readily applicable to any
`monoclonal antibody for which the cDNA has been cloned
`and for which a homologous human framework can be
`identified in the sequence data bases. It is also interesting to
`note that expression in the nonlymphoid Chinese hamster
`ovary cell line results in an antibody with demonstrable
`activity in ADCC. The capacity of this cell line for high-level
`expression of reshaped antibodies (16) should facilitate the
`large-scale production of this antibody for clinical studies.
`
`

`

`Immunology: Gorman et al.
`
`Proc. Natl. Acad. Sci. USA 88 (1991)
`
`4185
`
`We thank the following for their helpful discussions and assistance:
`G. Winter and P. Jones for the vectors M13-VKPCR1 and M13-
`VHPCRl, J. S. Crowe for Campath-lH cDNA, M. Page for the
`plasmids pLD9 and pNH316, J. Ivanyi and J. Howard for the cell line
`NB2-6TG, A. Lesk, and C. Chothia. We thank H. Spence for
`synthetic oligonucleotide synthesis, H. Kruger-Gray for flow cytom-
`etry assistance, and M. Frewin for technical assistance. This work
`was supported by the Medical Research Council, United Kingdom,
`Wellcome Biotech PLC, and the Gilman Foundation. S.D.G. is a
`recipient of a Special Fellowship from the Leukemia Society of
`America.
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