Use of beta-Iactamase

Field of the invention

The present invention relates to reducing the adverse effect of antibiotics on the normal microbiota in the intestinal tract. More precisely it refers to the use of class A beta-lactamase for preparing a medicament for reducing side-effects in the intestine. A method of reducing side-effects of unabsorbed beta-lactam antibiotic in the intestine is also disclosed.

Technical background

Beta-factam antibiotics are among the most widely used antibiotics against bacterial infections. They all share a common structural feature, that is they contain a beta-lactam nucleus. Beta-lactam antibiotics inhibit the biosynthesis of the bacterial cell wall, whiie possessing very low toxicity to the host. However, one problem associated with beta-lactam therapy is that many bacteria produce an enzyme called beta-lactamase, which is capable of inactivat- ing the beta-lactam antibiotic by hydroiyzing the amide bond of the beta-lactam ring.

The increase in the prevalence of beta-lactamase-producing strains of gram-positive and gram-negative bacteria has restricted the usefulness of beta-lactam antibiotics. Therefore pharmaceutical compositions containing combinations of beta-lactam antibiotics with beta-lactamase inhibitors have been developed to provide effective therapy independent of beta-lactamase producing bacteria. Known combinations are e.g. amoxicillin and clavulanic acid, ampicilϋn and sulbactam, piperacillin and tazobactam, and ticarcϊilin and clavulanic acid (Higgins et aL, 2004), Another problem associated with antibiotic treatment is that when the antibiotics reach the intestine tract they promote antibiotic resistance by exerting a selective pressure on the gut microbiota. Not only orally but also parenteraily administered beta-lactams may have adverse effects on the composition of the intestinal microbiota, presumably because they are secreted into the bile in appreciable concentrations. From the bile they are excreted into the gut, where they may cause disruption of the normal intestinal microflora. The disturbances in the ecoiogical balance between host and intestina! microbiota may lead to antibiotic associated diarrhea, overgrowth of pathogenic bacteria such as vancomycin resistant enterococci, extended beta-lactamase pro- ducing gram-negative bacilli or emergence and spread of antibiotic resistance

among the norma ⁾ intestinal microbiota or pathogens (Sullivan et a/., 2001 , Doπskey, 2006).

One strategy to reduce disarrangements in the intestinal microbiota is to select antimicrobial agents with minimal biliary excretion during parenteral antibiotic therapy (Rice βt ah, 2004). Another strategy includes the use of pro- biotics. A number of different probiotics have been evaluated in the prevention and reduction of antibiotic-associated diarrhea in adults and children, including the nonpathogenic yeast Saccharomyces boulardii and multiple iactic-acid fermenting bacteria such as Lactobacillus rhamnosus GG (LGG). S. boulardii treatment appears to prevent antibiotic-associated diarrhea recurrent C. difficile infection in aduits, whereas LGG is useful in the treatment of antibiotic- associated diarrhea in children (Katz, 2006). A further strategy encompasses bovine colostrum-based immune milk products, which have been proven effective in the prophylaxis against various antibiotic associated intestinal infections (Korhonen et a/. , 2000).

A still further strategy to avoid the adverse effects of beta-lactam antibiotics in the gut is coadministration of the antibiotic with a beta-factamase. Orai administration of beta-lactamase makes it possible to inactivate unab- sorbed beta-lactams in the gastro-intestinal tract, whereby their side-effects in- eluding alterations in the intestinal normal microbiota and the overgrowth of beta-iactam resistant bacteria is reduced. The beta-lactamase is conveniently formulated so as to be released in a desired section of the gastro-intestinal tract (WO 93/13795).

Orally administered beta-lactamase in conjunction with parenteral ampicilϋn therapy in canines has been shown to degrade biliary excreted am- picilϋn in a dose dependent manner without affecting arnpicillin levels in serum (Harrnoinen et a!., 2003). Moreover beta-lactamase therapy has also been illustrated to prevent antibiotic induced alterations in fecal microbiota during several days of treatment with parenteral ampicillin in a canine model (Har- moinen et a/., 2004). Comparable results have also been obtained by employing beta-lactamase colon targeted dosage forms (US 2005/249716).

The beta-lactamase employed in the studies performed by Har- moinen et a!., 2003 and 2004 is recombinant Bacillus iicheniformis beta- lactamase (PenP), which belongs to the Ambler class A enzymes (Ambler, 1980). It possesses high hydrolytic activity against penincillins, aminopenicillins such as ampiciSSin and amoxicillin and ureidopeniciliin such as piperacillin.

However, it is easiiy inactivated by common beta-lactamase inhibitors such as sulbactam, ciavulanic acid and tazobactarn.

Beta-iactamase inhibitors are effective in preventing inactivation of beta-!actams by beta-iactamase producing bacteria. Beta-lactamase inhibitors may therefore be combined with beta-lactams. In genera!, both components of such a combination have rather simϋar pharmacokinetic parameters with respect to various fiuids and tissues of the body and rather similar elimination half-lives, which are considered an essential prerequisite for the therapeutic efficacy of combination preparations. However, with respect to the biliary elimin- ation the pharmacokinetic properties of beta-Sactam and beta-iactamase inhibitors were found to vary. For instance the ratio of sulbactam to ampicillin was found to be nearly constant (approx. 1 :2} in serum, whereas the sulbac- tam/ampicillin ratios in the bile ranged from 1 :3 to 1:13 (Wildfeuer et ai. 1988). Despite the high variations in their ratios in the bϋe, the combination of beta- lactam with beta-iactamase inhibitor has been regarded as safe and effective therapy against infections in the biliary tract (Morris et a!., 1986., Brogard et al., 1989, Westphai et al., 1997).

It may be concluded from the above that the effect of beta-iactarn antibiotics has been enhanced by combining them with beta-lactamase inhibi- tors to reduce the effect of beta-lactamases that otherwise inactivate the antibiotic. Further there has been suggested a number of ways to reduce the adverse side-effects of antibiotic treatment such as disturbing the microbiota in the intestine. Still there is a need for more effective antibiotic treatments without adverse side-effects. The present invention meets these needs. It reduces the risks of superinfections and of increasing antibiotic resistance associated with the use of beta-lactam antibiotics.

Summary of the invention

The present invention relates to beta-iactam antibiotic therapy, which is not susceptible to inactivation by beta-lactamase producing bacteria, and which does not disrupt the balance of the normal microbiological flora in the intestine, it has now been found that beta-lactamase is effective in inactivating residual beta-iactam in the intestine in connection with antibiotic treatment with a combination of beta-lactam antibiotic and beta-lactamase inhibitor. This was surprising; because it was known that beta-!actams and their tnhibi- tors are partially eSiminated from the body via the bile into the small intestine, and that said inhibitors inactivate beta-lactamase in vitro.

The present invention provides the use of ciass A beta-lactamase for the manufacture of a medicament for reducing side-effects in the intestine associated with treatment with a combination of beta-iactam antibiotic and beta-Sactamase inhibitor. The invention further describes a method of reducing side-effects in the intestine associated with treatment with a combination of beta-lactam antibiotic and beta-lactamase inhibitor, wherein an effective amount of class A beta-!actamase is administered to a subject in need thereof.

Specific embodiments of the invention are set forth in the dependent claims. Other objects, details and advantages of the present invention will become apparent from the following drawings, detailed description and exam- pies.

Brief description of the drawings

Figure 1 shows the nucleotide sequence and deduced amino acid sequence of the Bacillus licheniformis beta-lactamase gene cloned in secretion vector pKTH 141.

Figure 2 shows the ampicillin concentration in jejunal chyme in beagle dogs after parental administration of a combination of ampiciϋin/sulbactam in the absence or presence of orally administered beta-lactamase. Figure 3 shows the amoxicillin concentration in jejuna! chyme in beagie dogs after parental administration of a combination of amoxicii- lin/clavuianic acid in the absence or presence of orally administered beta- iactamase.

Figures 4 and 5 show the piperacillin concentration in jejunal chyme in beagle dogs after parental administration of a combination of piperacil- ϋn/tazobactam in the absence or presence of orally administered beta- lactamase at different doses.

Detailed description of the invention

The present invention relates to the use of orally administered beta- lactamase for the preparation of a medicament for reducing the adverse effects on the intestinal microbiota of residual unabsorbed beta-iactam antibiotic derived from therapy with a combination of beta-lactam antibiotic and beta-lactamase inhibitor. The orally administered pharmaceutical composition of beta- lactamase is intended to reduce the effects of a beta-!actam/beta-lactamase inhibitor combination on the major intestinal microbiota in the distal part of il-

eum and in the colon, and as foilows to maintain the ecological balance of the intestinal microbiota. Hence, by employing beta-iaciamase therapy, side effects associated with residual unabsorbed beta-lactam/beta-!actamase inhibitor in the small intestine and colon are prevented. Beta-!actamase

Beta-laclamase is a beta-lactam hydrolase enzyme classified as EC 3.5.2.6. The beta-lactamases are further classifed on the basis of their amino acid sequence into four classes A, B, C and D (Ambler, 1980). Classes A, C and D are also called serine beta-iactamases, because they have a serine residue in their active site. Along their primary structures, three conserved peptide sequences, important for recognition of the substrate or catalysis, have been identified by comparison of the 3D structures (Colombo et al., 2004):

Beta-lactamase Element

1 2 3

Class A SXXK SD(N/S/G) (K/R/H XTVS) G

Class C SXXK YAN KTG

Class D SXXK SXV K(T/S)G

The first element is uniform among ail serine beta lactamases, it contains active-site serine (S) and lysine (K) whose side chain points into the active site. The second element forms one side of the catalytic cavity. !t is called the SDN loop in class A beta lactamases. The SDN loop is nearly invariant among ciass A enzymes apart from a few exceptions. The third ele- ment is on the innermost strand of the beta-sheet and forms the opposite wall of catalytic cavity. It is generally KTG. Lysine (K) can be replaced by histidine (H) or arginine (R) in a few exceptional cases, and threonine (T) can be substituted by serine (S) in several class A beta lactamases (Matagne et al., 1998). According to one embodiment of the invention the class A beta- lactamase is derived from a Bacillus species. According to a particular embodiment of the invention the class A beta-lactamase is Bacillus licheniformis PenP. This enzyme has been described i.a. by Izui et a/., 1980, and it may be derived e.g. from S. licheniformis 749/C (ATCC 25972). The amino acid sequence of PenP from strain 749/C is set forth in the protein sequence data- base Swiss-Prot as sequence number P00808. It is also given here, as SEQ

ID NO: 1. The nucleotide sequence of the corresponding penP gene is given in the DDBJ/ESV1BL GenBank database as sequence V00093. The S. licheni- formis beta-lactamase is a lipoprotein, which is anchored to the cytoplasmic membrane of the Bacillus through a fatty acid tail in such a way that the protein part is folded outside the membrane. SEQ ID NO:1 sets forth the fuii length amino acid sequence of the protein, inciuding the 26 amino acids long signal sequence. This form is the precursor lipoprotein. Diacylgiyceride is covalently linked to the NH2-terminai cysteine (C) at position 27 resulting in the lipoprotein form. in addition there are shorter forms of the protein that are secreted outside the ceil. These are also caϋed exoforms. The exoforms are the result of hydroiytic activity of proteases in the cell wall or culture medium.

"PenP" as used herein encompasses any beta-lactamase active fragment and/or variant of the explicitly given amino acid sequence (SEQ ID NO: 1 ). Especially it is an N-truncated form of the sequence, which means that it has been truncated at the aminoterminus. In addition to the N-truncation, it may comprise one or more further amino acid deletions, substitutions and/or insertions, as long as it has beta-lactamase activity. Said modifications may be either naturally occurring variations or mutants, or artificial modifications intro- duced e.g. by gene technology. Differently aminoterminaϊly truncated exoforms have been found in the growth medium of β, Sicheniformis. Such exoforms are also encompassed herein by the term PenP. Matagne ef a/., 1991 have described various extents of mfcroheterogeneity in extracellular forms produced by the natural host S. licheniformis 749/C. The following five different secreted exoforms with different N-terminal amino acid residues were identified:

SQPAEKNEKTEMKDD KALNMNGK (amino acids 35-49...300-307 )

EKTEMKDD KALNMNGK (amino acids 42-49...300-307)

KTEMKDD KALNMNGK (amino acids 43-49...300-307) EMKDD.....KALNMNGK (amino acids 45-49...300-307 )

MKDD KALNMNGK (amino acids 46-49...300-307)

lnitiai amino acid residues are presented in boid. The C-termina! amino acid residues are indicated to the right. The amino acid positions refer to SEQ ID NO: 1. The exoform starting from serine (S) at position 35 is called the

"large secreted form" of S. licheniformis beta-iactamase, and the one starting

from lysine (K) at position 43 is called the "small secreted form". The first aipha helix (α _r hβϋx} starts from aspartatic acid (D) at position 48 and the end of the last aipha helix (an -helix) ends at asparagine (N) at position 303. According to one embodiment of the invention PenP comprises at least the amino acids 48 to 303, which take part in the secondary structure of the protein (Knox et a!,, 1991 ) According to another embodiment of the invention one or more of said amino acids 48 to 303 have been deleted or replaced.

According to still another embodiment of the invention the amino terminal of PenP begins with NH ₂ -KTEMKDD (amino acids 43-49 of SEQ ID NO: 1 ). This so-called ES-betaL exoform may further lack up to 21 contiguous residues as described by Gebhard et a/., 2006. According to another embodiment of the invention the amino terminal begins with glutamic acid (E) of SEQ ID NO: 1 , and especially it begins with NH ₂ -EMKDD (amino acids 45-49 of SEQ ID NO: 1), or alternatively it begins with NH ₂ -MKDD (amino acids 46-49 of SEQ !D NO:1).

The four last amino acids at the carboxylic end of the PenP protein MNGK-COOH are not part of the secondary structure, and may therefore also be deleted without loosing activity. !n another embodiment up to nine C- terminal amino acids may be deleted. C-truncated forms of the protein have been described by Santos et ai, 2004.

Ai! the different forms set forth above of the beta-lactamase are encompassed by the term PenP as used herein, together with other forms of the protein having beta-lactamase activity. According to one specific embodiment of the invention the beta-lactamase has an amino acid sequence that has at least 40, 50, 60, 70, 80, 90, 95, 97, 98 or 99 % sequence identity to SEQ ID NQ: 1 or to a beta-lactamase active fragment thereof, especially to the mature fragment of the protein starting at position 27, and preferably to an N-truncated fragment of the protein starting at a position corresponding to position 45 or 46 of SEQ ID NO:1. The sequence identity is determined using BLAST (Basic Lo- cal Alignment Search Tools) as described in Aitschu! et al., 1997.

Beta-lactamase activity may be determined by nitrocefin assay as described by O'Caiiaghan et a/., 1972.

The class A beta-lactamase is conveniently produced as a recombinant protein. Preferably it is produced in a Bacillus host strain that is suitable for producing pharmaceutical products such as S. amyioiiquefaciβns, S. pυmu- Hs, or S. subtiiis. One way of producing beta-lactamase in a non-sporuiating B.

subtϋis strain is described in WO 03/040352. The protein may also be homolo- gousiy produced in S. licheniformis by overproduction.

Formulation

The beta-lactamase is conveniently formulated into an enteric coated, oraliy administered pharmaceutical composition, e.g. as gastro resistant beta-lactamase pellets, to obtain a targeted beta-lactamase formulation. According to one embodiment of the invention the beta-iactamase is conveniently administered as enteric coated pellets filled in e.g. hard gelatine capsules. Enteric coating dosage forms are well-known among oral products in the pharmaceutical industry. The drug products with enteric coatings are designed to bypass the stomach in intact form and to release the contents of the dosage form in the small intestine, i.e. duodenum, jejunum and/or ileum. The reasons for applying enteric solid formulations are to protect the drug substance from the destructive action of the gastric enzymes or iow pH environment of the stomach, or to prevent drug substance-induced irritation of gastric mucosa, nausea or bleeding, or to deliver drug substance in undiluted form at a target site in the small intestine. Based on these criteria, enteric coated drug products can be regarded as a type of delayed action dosage forms. Aqueous-based coating forms appear to be the most favorable materials for a coating process of the hydrophilic PenP protein. The aqueous polymers commonly used to achieve enteric properties are polymethacryiat.es such as Eudragit®, cellulose based polymers e.g. celiuiose ethers e.g. Duodceli® or cellulose esters, e.g. Aquateric® or polyvinyl acetate copymers e.g. Opadry®.

Method of treatment The class A beta-lactamase is used for reducing side-effects in the intestine induced by a combination of beta-iactam antibiotic with beta- lactamase inhibitor. The enteric coated beta-lactamase is released in the intestine in an amount capable of eliminating unabsorbθd beta-iactam antibiotic, whereby adverse effects of the antibiotic are reduced. The beta-Sactamase for example reduces or prevents antibiotic associated disturbances in the ecological balance between host and intestinal microbiota, which may lead to diarrhea, overgrowth of pathogenic bacteria such as vancomycin resistant entero- cocci, extended beta-lactamase producing gram-negative bacilli or emergence and spread of antibiotic resistance among the norma! intestinal microbiota or pathogens. Beta-lactamase thus makes it possible to avoid superinfections by

e.g. Clostridium difficile and pathogenic yeast, which is of particular importance in immunosuppressed patients. The targeted, enteric coated beta-lactamase is suitably given orally in conjunction with parenteraliy or possibly orally administered antibiotics and beta-lactamase inhibitor. The subject to be treated with beta-lactamase is a human being or an anima! such as a farm animal that is treated with a combination of a beta-lactam antibiotic and an inhibitor of beta- iactamase.

Antibiotics and inhibitors

"Beta-lactam antibiotic" is an antibacterial compound containing a four-membered beta-lactam (azetidin-2-one) ring. Beta-lactam antibiotics are well known in the art, and they may be of natural, semisynthetic or synthetic origin. The beta-lactam antibiotics can be generally classified into penicillins, cephalosporins, cephamycins, oxa-beta~iactarns, carbapenems, carbace- phems and monobactams based on their further structural characteristics. Preferably the antibiotic is one that is administered parenteraliy. The beta-lactam antibiotic is combined with an appropriate beta-lactamase inhibitor. Suitable antibiotics for this purpose are e.g. penicillins including e.g. penicillin G , aminopenicillins such as amoxicillin and ampicillin, ureidopeniciliiπ such piperacillin or alpha-carboxypenicillin such as ticarcillin. "Beta-lactamase inhibitor" is a compound that is capable of inhibiting a beta-lactamase, which in turn is capable of hydrolyzing a beta-lactam antibiotic. The inhibitors are generally but not necessarily structurally related to beta- iactam antibiotics, and may have weak antibacterial activity per se, but their function in the combinatorial therapy is to protect the actual antibiotic from be- ing inactivated by bacterial beta-lactamases. In the present content the inhibitor is especially an inhibitor against class A beta-lactamases. Appropriate inhibitors are e.g. sulbactam, ciavulanic acid and tazobactam. Clavulanic acid is a natural analog, whereas sulbactam and tazobactam are semisynthetic. Most inhibitors are administered parenterafly, i.e. intravenously or intramuscularly. Clavulanic acid may aiso be administered orally. Several beta-lactam antibi- otic/beta-lactamase inhibitor combinations have been described In the art and clinically used.

The antibiotic and the inhibitor are conveniently administered as a mixture. Commercially available beta-lactamase inhibitors are clinically used in combination with various beta-lactams. Clavulanic acid is used in combination with amoxicillin or ticarcilϊin, similarly sulbactam is used with ampiciliin, and ta-

zobaciam with piperaciilin. Other combinations are also possible. Beta- lactamase may be administered orally simultaneously, or before the treatment with the antibiotic-inhibitor combination. Preferably it is administered simultaneously with the beta-iactam/inhibitor combination. Dosages

The degree of disturbance in the intestinal micrαbiota and the incidence of side effects due to administration of a combination of beta-iaciam and beta-lactamase inhibitor are dependent on a variety of factors, including drug dosage, route of administration, and pharmacokinetic/dynamic properties of the beta-lactam and the inhibitor. The beta-iactamase is administered in an amount efficient to reduce the side effects associated with residual unabsorbed beta-lactam in the smai! intestine and colon. In the experiments performed doses of about 0.1 mg of beta-iactamase/kg body weight were effective to eliminate ampicillin and amoxicillin to a concentration below the detection limit in jejunal chyme, whereas a higher dose is needed to eliminate piperaciilin. A suitable dose may be 0.1 - 1.0, especially 0.2 - 0.4 mg of beta-lactamase/kg body weight.

The invention is further illustrated by the following non-limiting examples. It should be understood, however, that the embodiments given in the description above and in the examples are for illustrative purposes only, and that various changes and modifications are possible within the scope of the invention. The test results show an unpredictable effect of beta-lactamase on unabsorbed beta-lactam in connection with beta-iactam/beta-iactamase inhibitor therapy. The results support extending the use of Bacillus Hcheniformis beta-lactamase to antibiotic therapy with combinations of beta-!actam with beta-lactamase inhibitor.

Example 1

Recombinant beta-iactamase derived from Bacillus Hcheniformis 749/C, was used in the experiments. The protein was produced in a non- sporulafing Bacillus subtilis strain as described in WO 03/040352.

A secretion vector pKTH141 was used, which comprises an expression cassette carrying a strong vegetative promoter (amyQ _p ), a ribosome- binding site (RBS), and a signal sequence encoding region (amyQ _ss ) of the β. amyloliquβfaciβns E18 amylase gene (amyQ). In addition a synthetic oligonu- cleotide with a single HindiW site was inserted directly at the 3'-end of the sig-

nal sequence encoding region. Thus the insert encoding foreign protein could be cloned into the HindlU site in such a way that it wiil be translated in the same reading frame as the signal sequence of alpha-amyiase. The HindWl oligonucleotide encodes three amino acid residues (NH2-QAS), which is ex- pected to comprise an NH ₂ -termina! extension of the mature protein.

The structural gene {penP) of Bacillus Ucheniformis beta-lactamase encoding sequential amino acid residues 43-307 of SEQ ID NO:1 was amplified by PCR with appropriate primers containing a HindlU restriction site using S. Ucheniformis chromosomal DNA as a template. The amplified fragment was subsequently cleaved with HindWl and ligated into the corresponding site of pKTH141 resulting in frame fusion between the sequence encoding the AmyG signal peptide and the PenP protein. The nucleotide sequences of the beta- lactamase gene were determined by the dideoxy-chain termination method with an automatic DNA sequencer. The complete nucleotide and deduced amino acid sequences of the recombinant B. Ucheniformis 749/C beta-lactamase gene are set forth as SEQ ID NO: 2 and 3, and presented in Figure 1.

Sn Figure 1 the numbers below the line and shown in parentheses refer to the amino acid residues. The HindlW cloning site that encodes an NH ₂ - QAS extension, is presented above the nucleotide sequence. The predicted signai peptidase cleavage site is after alanine at position of -31.

The open reading frame encodes a 299 amino acid polypeptide possessing a 31 amino acid residues long signal sequence of the amyQ gene. The cleavage site of signai peptidase is predicted to locate after alanine at position of -1. The mature beta-!actamase was expected to start from giutamine (Q) at position +1. Accordingly, the mature beta-lactamase was expected to contain 268 amino acid residues of which the NH ₂ -QAS extension is encoded by the Hind\\\ cloning site.

The NH ₂ -terminai sequence of purified recombinant beta-lactamase was determined by automated Edman degradation with a protein sequenator. Analysis revealed that the recombinant beta-lactamase lacks the NH ₂ -QASKT- pentapeptide at its deduced amino terminus. The result indicates that the truncated form of the recombinant beta-lactamase protein is generated by post translational action of proteolytic enzymes which are present both in the bacterial eel! wall and in the culture medium. To conclude, the major part of the puri- fied recombinant beta-lactamase composes 263 amino acid residues, and has a molecular mass of 29.3 kDa. The determined amino terminal sequence starts

after five amino acid residues downstream from the deduced amino acid sequence. The initial amino acid residue of purified recombinant beta-factamase is glutamic acid (E) at position +6 in Figure 1.

The purified enzyme protein is named P1A. It consists essentially (at least about 95 weight-%) of sequential amino acid residues 45 to 307 of SEQ ID NO: 1. The rest consists essentially of sequential amino acid residues 46 to 307 of SEQ ID NO: 1. The beta-iactamase was administered in the form of enteric coated pellets essentially similar to the peiiets utilized in the studies performed by Harmoinen et a/., 2004, The capability of S. licheniformis beta-lactamase to eliminate biliary excreted ampicillin in the small intestine during parenteral therapy with a arn- piciilin-sulbactam combination was investigated in a canine model. A nipple valve was surgically inserted in jejunum of laboratory beagles approximately 170 cm distal to pylorus to enable cotJection of samples for analysis. The intes- final surgery did not alter the intestinal motility. Six beagle dogs were utilized throughout the study. The study was performed as two sequential treatments: In the first experiment, two consecutive doses of a combination of ampicillin with sulbactam (40 mg of ampiciϋin and 20 mg of sulbactam per kg of body weight) were administered intravenously at dosing intervals of 6 hours 20 min- utes after feeding. Seven days later, a second experiment was performed similar to the first experiment, except that the same dogs were additionally orally administered beta-lactamase 10 minutes prior to the ampiciilin/suibactam injection, A single dose of enteric coated pellets containing about 0.1 mg of active beta-lactamase per kg of body weight was used. Jejunal chyme samples were collected at various time points.

Chyme samples were immediately frozen and stored at -7O ⁰ C to await analysis. The chyme samples were cleaned up by solid phase extraction, A reverse- phase high performance liquid chromatography (HPLC) method with UV detection was used for the quantification of ampiciilin. The obtained results showed that high levels of ampicillin were detected in the Jejunal samples in the first experiment performed without beta- lactamase therapy whereas the second experiment showed that orally administered beta-Sactamase is capable to reduce jejunal ampiciliin levels below the limit of quantification (10 micrograms of ampicilfin per gram of jejunal chyme). Figure 2 shows the effect of orally administered beta-lactamase pellets (dose of about 0.1 mg of active beta-lactamase per kg of body weight) on

the concentrations of ampiciliin in jejunal chyme of beagle dogs (n=6) after intravenously administrations of an ampicillin/suibactam combination (40 mg of ampiciliin and 20 mg of sulbactam per kg of body weight). The values for both experiments are presented as mean jejunal ampiciliin concentrations at differ- ent time points. Ampiciliin values in experiment 1 represent jejunal ampiciilin concentrations achieved after two separate administrations of ampiciiiin/sul- bactarn at a dosing interval of 6 hours without beta-lactamase treatment. Beagle dogs were treated with an ampiciilin/sutbactam combination with concurrent beta-Saciamase therapy in experiment 2. The employed dose of beta- lactamase is capable of eliminating a major part of jejuna! ampiciliin in beagle dogs during the first ampiciliin/sulbactam treatment, and concentrations dropped and remained below the quantification level throughout the second ampiciϋin/suibactam treatment with concurrent beta-iactamase therapy.

The results show that residual biliary excreted beta-lactamase in- hibitor possesses limited influence on the activity of the beta-lactamase.

Example 2

The effectiveness of B. licbeniformis beta-iactamase P1A to inactivate biliary excreted amoxicillin during parenteral therapy with a combination of amoxicillin with clavulanic acid was investigated essentially similarly to Exam- pie 1 , except that a single dose of an amoxicilitn/ciavulanic acid combination contained 25 mg of amoxicillin and 5 mg of clavulanic acid per kg of body weight, and the HPLC analysis method was elaborated to be suitable for analysis of amoxicillin (the limit of quantification was 2 micrograms per gram of jejunal chyme). The obtained results are presented in Figure 3, which shows the effect of oraify administered beta-Sactamase pellets on the concentrations of amoxicillin in jejunal chyme of beagle dogs (n=6) after intravenously administrations of an amoxiciilin/clavulanic acid combination (25 mg of amoxicillin and 5 rπg of clavuianic acid per kg of body weight). The values for both experi- ments are presented as mean jejunal amoxicillin concentrations at different time points. Amoxicillin values in experiment 1 represent jejuna! amoxicillin concentrations achieved after two separate administrations of amoxiciilin/clavulanic acid at a dosing interval of 6 hours without beta-lactamase treatment. Oral beta-lactamase treatment was combined with parenteral therapy of amoxiciilin/clavulanic acid combination in experiment 2.

!t was found that beta-lactarnase treatment was abie to eliminate a major portion of biliary excreted amoxicillin during parenteral therapy with an amoxiciiiin/clavulanic acid combination. The traces of amoxicillin found in some jejunal samples at different time points can be eliminated by increasing the dose of beta-lactamase. The results suggest that β. licheniformis beta- lactamase is a potent candidate as a drug substance for reducing the side effects related to the use of parenteral amoxicillin/ciavulanic acid.

Example 3

Beagle dogs were treated with a combination of piperacillin and ta- zobactam without and with simultaneous beta-lactamase therapy. The experiments were performed essentially as those described in Examples 1 and 2, except that a single dose of the piperaciiliπ/tazobaciam combination contained 100 mg of piperacillin and 12.5 mg of tazobactam per kg of body weight, and the HPLC analysis method was elaborated to be suitable for analysis of piper- aciilin (the limit of quantification was 10 micrograms per gram of jejuna! chyme).

The results are presented in Figure 4, which shows the effect of oraliy administered beta-lactamase peilets on the concentrations of piperacillin in jejunal chyme of beagle dogs (n=6) after intravenously administrations of a piperacilϋn/tazobactam combination (100 mg of piperacillin and 12,5 mg of ta- zobactam per kg of body weight). The values for both experiments are presented as mean jejuna! piperacillin concentrations at different time points. Piperaciϋin values in experiment 1 represent jejunal piperacillin concentrations achieved after two separate administrations of piperacililn/tazobactam at a dosing interval of 6 hours without beta-iactamase treatment Beagle dogs were treated with a piperaciilin/tazobactam combination with concurrent beta-lactamase therapy in experiment 2.

The results obtained without beta-factamase (experiment 1 ) showed that the biliary elimination of piperacillin in beagle dogs is considerably higher than that of ampiciltin or amoxicillin. Nevertheless the beta-lactamase treatment reduced the jejuna! piperacillin concentrations at al! time points. However, piperacillin concentrations remained detectable throughout the beta- lactamase treatment (experiment 2). Accordingly, the obtained results showed that beta-tactamase therapy is capable to eliminate jejunal piperacillin during parenteral therapy with a piperacilSin/fazobactam combination, but the quantity of beta-iactamase in enteric coated pellets should be increased in order to

achieve a dosage formulation that is abie to eliminate jejunal piperacillin concentration below the quantification limit.

The experiment was repeated except that the single dose of beta- lactamase peilets contained about 0.3 mg of active beta-iactarnase per kg of body weight, and the single dose of the piperacillin/tazobactam combination contained 65.6 mg of piperacillin and 9,4 mg of tazobactam per kg of body weight The results are presented in Figure 5, which shows that the beta- factamase was very efficient in eiiminatiπg jejunal piperacillin.

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