Points to Consider in the Production and Testing of New Drugs and

DRAFT

APRIL 10, 1985

Points to Consider in the Production and Testing of

New Drugs and Biologicals Produced by Recombinant DNA Technology

Office of Biologics Research and Review

Center for Drugs and Biologics

-2- DRAFT

APRIL 10, 1985

Table of Contents

I. Introduction

II. General Considerations

III. Expression Systems

IV. Master Cell Bank

V. Production

VI. Purification

VII. Characterization of the Product

A. Physicochemical Characterization of Proteins

B. Biological Tests for Identity and Potency

C. Tests for Contaminants

D. Preclinical Toxicity Evaluation

VIII. Modified Protein Products

IX. Clinical Trials

-3- DRAFT

APRIL 10, 1985

I. Introduction

This document provides suggestions for evaluating safety, purity, and

potency of new drugs and biologics produced by recombinant DNA technology.

The suggestions expressed herein are expected to change with time as new

knowledge is acquired, and should not be regarded as being either definitive

or all-inclusive. Accordingly, the points discussed below should be

interpreted as those that manufacturers of such products are generally

expected to consider during development of new drugs and biologics, in filing

notices of claimed investigational exemptions for new drugs (IND), in new drug

applications (NDA), and in license applications.

II. General Considerations

General regulations for biologics (e.g. 21 CFR, Chapter I, Subchapter F)

and drugs (e.g. 21 CFR, Chapter I, Subchapters C and D) also pertain to

products produced by recombinant DNA technology where applicable. Specific

concerns relevant to particular products should be discussed with the

appropriate Office on a case-by-case basis. New license applications or new

drug applications are required before marketing products made with recombinant

DNA technology, even if the active ingredient in the product is thought to be

identical in molecular structure to a naturally occurring substance or a

previously approved product produced in an established manner.

The production of new drugs and biologics by recombinant DNA technology

should generally follow the NIH Guidelines for Research Involving Recombinant

DNA Molecules. In addition, manufacturers wishing to export their products

from the United States should consult the appropriate guidelines published by

agencies such as the World Health Organization, and the National Institute for

Biological Standards and Control (United Kingdom).

-4- DRAFT

APRIL 10, 1985

III. Expression Systems

Recombinant DNA technology involves the systematic arrangement and

manipulation of specific segments of nucleic acid for construction of

composite molecules which, when placed into an appropriate host environment,

will yield a desired product. There are three general methods for obtaining a

specific coding segment: (a) reverse transcription of mRNA to complementary

DNA; (b) isolation of genomic DNA or RNA; or (c) chemical synthesis.

The manufacturer should provide a description of the method used to

prepare the segment coding for the desired product, including both the cell

type and origin of the source material. A detailed nucleotide sequence

analysis, and a restriction enzyme digestion map of the cloned segment should

also be included. If a cloned polynucleotide contains more information than

coding sequences, i.e. introns or flanking sequences, then these additional

sequences should be adequately characterized.

The construction of the vector used for expression of the cloned

nucleotide segment into its respective product should also be described. This

description should include a detailed explanation of the source and function

of the component parts of the vector, e.g. origins of replication, antibiotic

resistance genes, promoters, enhancers, whether or not the product is being

synthesized as a fusion protein. A restriction enzyme digestion map

indicating at least those sites used in construction of the vector should be

provided.

The host cell system which will generate the product is coordinated to

fit the expression vector. It is, therefore, important that a description of

the source, relevant phenotype and genotype of the host be provided, including

-5- DRAFT

APRIL 10, 1985

literature references. If the host cell is of mammalian origin then it should

be thoroughly characterized.

Various methods can be utilized to transfer an

expression vector into its host, such as transfection, transduction,

infection, microinjection, etc. The mechanism of transfer, copy number, and

the physical state of the vector inside, the host cell, integrated or

extrachromosomal, should be provided.

IV. Master Cell Bank

The Master Cell Bank is a designated seed lot, from which all subsequent

seed lots are made. A seed lot consists of aliquots of a single culture,

stored in a manner which gives a reasonable assurance of genetic stability.

In most cases, a single host cell containing the expression vector should be

cloned to give rise to the Master Cell Bank. The cloning history and

methodology should be described. If new Master Cell Banks are to be generated

periodically by expression vector transfer and clonal selection, acceptance

criteria for both the new clones and the product produced by these clones

should be described. The stability of both the host cell and expression

vector should be investigated. In particular, the fidelity of the nucleotide

sequence encoding the expression product in the Master Cell Bank should be

verified. Whenever clonal selection is used to construct a new seed lot, DNA

sequence analysis of the coding region should be performed.

In cases in which there is multiple integration into the host cell

genome of the DNA sequences expressing the protein product, thus making these

sequences difficult to characterize, the mRNA encoding the specific product

should be cloned and the anticipated coding sequence of the product should be

verified, for each Master Cell Bank.

-6- DRAFT

APRIL 10, 1985

The identity and purity of the cells in each seed lot should be assured

by isoenzyme analysis, auxotrophy, antibiotic resistance, and karyology, as

appropriate.

Each seed lot should be characterized for adventitious agents including

mycoplasma, bacteria, fungi, viruses, and virus-like particles.

V. Production

The cells used in each production run should be characterized by

analysis of relevant phenotypic or genotypic markers, and tested for

adventitious agents in samples taken just prior to termination of culture.

Additionally, a detailed restriction enzyme digestion map of the expression

vector and the nucleotide sequence of the insert encoding the expression

product should be determined after full scale culture at least once for each

Master Cell Bank.

The procedures and materials used for cell growth and induction of

product expression should be described in detail.

Data on the consistency of yield of the product from full-scale culture

should be maintained, and criteria for the rejection of culture lots should be

established.

Penicillin and other beta-lactam containing antibiotics may derivatize

proteins and generally should not be used in production runs because of the

risk of hypersensitization in product recipients. Similarly, caution should

be exercised in the use of such materials as phenylmethylsulphonylfluoride

(PMSF, a protease inhibitor), b-propiolactone, formaldehyde and other protein

derivatizing chemicals, since multiple exposure to derivatized proteins may

lead to undesirable immune responses in recipients of the final product.

VI. Purification

The methodology of harvesting, extraction, and purification should be

-7- DRAFT

APRIL 10, 1985

described in detail, and the removal of any undesirable chemicals introduced

by these procedures should be demonstrated.

The extent of purification of recombinant DNA products should be

consistent with the intended use of the product. Drugs and biologics which

are to be administered repeatedly or at high concentrations should be

adequately pure to prevent the development of undesired immune or toxic

reactions to contaminants. Although recombinant DNA products may be

demonstrated to be 99% pure by physicochemical characterization, special

attention should be directed toward the removal of certain contaminants which

may be present in small amounts. The purification process should be designed

to specifically eliminate detectable viruses, microbial and nucleic acid

contamination and undesirable antigenic materials.

The use of antibodies for affinity purification of recombinant DNA

products deserves special comment. The antibodies should be shown to be free

from unwanted biologically active substances such as DNA and viruses as

described in Section VII, C.

Methods used for the coupling of the antibody to

the column matrix and the removal of contaminants from the affinity column

should be described. Several production lots of the final product should be

examined for the absence of detectable immunoglobulin protein.

VII. Characterization of the Product

Evidence for identity, purity, and stability of the product in

comparison with reference preparations may be derived from the results of a

wide variety of tests. The specific tests that will adequately characterize

any particular product on a lot to lot basis will depend on the nature of the

product. Some examples of tests which may be useful during product

development or lot to lot testing are described below.

-8- DRAFT

APRIL 10, 1985

A. Physicochemical Characterization of Proteins

1. Amino Acid Composition Analysis

The complete amino acid composition of the peptide or

protein should include accurate values for methionine 1/2-cystine and

tryptophan, which may require sample preparation procedures other than

hydrolysis in 6N HCl or chemical modification of proteins and analysis of

derivitized amino acids. The amino acid composition presented should be the

average of at least three (3) separate hydrolysates of each lot number.

For small proteins or peptides with molecular weight less

than 10,000, the demonstration of nearly integral ratios of amino acids would

support arguments of peptide purity.

For proteins with molecular weight in excess of 10,000 the

amino acid composition analysis may not provide as useful information in

support of the purity of the product as for the small proteins or peptides.

However, integral values for those amino acid residues generally found in low

quantities» such as tryptophan and/or methionine, could be obtained and used

to support arguments of purity.

2. Partial Sequence Analysis

Where possible, partial amino terminal (15 residues) and

carboxy terminal sequence analyses can serve as important criteria for the

identity of recombinant DNA produced proteins or peptides. The sequence data

presented in tabular form should include the total yield for every amino acid

at each cycle, as well as the repetitive yield for the major sequence(s). In

several cases. unexpected heterogeneity in the amino termini and carboxy

termini of proteins produced by recombinant DNA technology has been observed

by using protein sequence analysis.

-9- DRAFT

APRIL 10, 1985

3. Peptide Mapping

Peptide mapping can provide a very discriminating comparison

between a recombinant DNA product and an authentic sample of the natural

product or a reference preparation. In conjunction with amino acid

composition and sequence analysis of each peptide, peptide mapping can provide

precise evidence for the identity of a protein. For proteins containing

disulfide bonds, peptide mapping often can be used to verify the correct

arrangement of disulfide bonds in the final product.

4. Polyacrylamide Gel Electrophoresis (PAGE) and Isoelectric

Focusing

PAGE and isoelectric focusing are valuable techniques for

verifying identity, purity and apparent molecular weight of proteins and

peptides. The PAGE analysis should include the use of denaturing conditions

with and without exposure to reducing agents, and with appropriate molecular

weight standards or reference preparations.

It is preferable to analyze samples on slab gels stained by

an appropriately sensitive method: for example, silver stain is generally more

sensitive than Coomassie blue for the detection of very small quantities of

proteins and is useful in identifying nonprotein materials such as nucleic

acid, carbohydrate and lipid which may be present.

For peptides of molecular weight less than ca. 8,000, most

PAGE methods may not be sufficiently accurate for molecular weight estimates.

5. High Performance Liquid Chromatography (HPLC)

HPLC is a useful method to determine the purity of a protein

or peptide, to evaluate its molecular configuration and, under some

circumstances, to confirm its identity. HPLC may be especially useful in

-10- DRAFT

APRIL 10, 1985

characterizing and quantitating specific impurities in the final product, and

in peptide mapping.

6. Circular Dichroism and Optical Rotatory Dispersion (CD and

ORD)

A comparison of the CD or the ORD spectrum of the material

prepared by recombinant DNA technology with the corresponding spectrum of the

native material or a reference preparation may support conformational

similarity.

7. Other Characterization

Additional physicochemical characterizations may be

appropriate for recombinant DNA products containing carbohydrates, DNA,

lipids, and other nonprotein components.

B. Biological Tests for Identity and Potency

A comparison of the recombinant DNA product to the natural product

or reference preparation in a suitable bioassay will provide additional

evidence relating to the identity and potency of the recombinant DNA product.

Various types of bioassay may be used. In vitro assays are usually faster,

less expensive, and more precise than animal studies, yet adequate testing of

a biological product may involve animal studies.

Most vaccines produced by recombinant DNA techniques should be

compared to the natural substance or reference preparations with respect to

their ability to promote immune responses in animals. Non-vaccine recombinant

DNA products may be compared with the natural product in pharmacokinetic

studies including tissue distribution and clearance mechanism. The extent,

frequency and methods of animal testing should be determined on a case-by-case

basis.

-11- DRAFT

APRIL 10, 1985

C. Tests for Contaminants

Reliable and sensitive tests will be needed to assay for trace

contamination and product related impurities in the final product on a lot to

lot basis. Although physiochemical characterization can ensure a high degree

of purity of a recombinant product, tests for trace contaminants will rely

heavily on biological indicator systems.

1. Pyrogen Contamination

Pyrogenicity testing should be conducted by injection of

rabbits with the final product or by the limulus amebocyte lysate (LAL)

assay.

Criteria comparable to those adopted for acceptance of the natural

product should be used for the recombinant DNA product.

Certain biological pharmaceuticals are pyrogenic in humans

despite having passed the LAL test and the rabbit pyrogen test. This

phenomenon may be due to materials which appear to be pyrogenic only in

humans. To attempt to predict whether human subjects will experience a

pyrogenic response, human blood mononuclear cells can be cultured in vitro

with the final product and the cell culture fluid injected into rabbits. A

fever in the rabbits indicates that the product contains substances which may

be pyrogenic in humans.

2. Viral Contamination

Tests for viral contamination should be appropriate to the

cell substrate and culture conditions employed.

Absence of detectable

adventitious viruses contaminating the final product should be demonstrated.

3. Nucleic Acid Contamination

Removal of nucleic acid at each step in the purification

process may be demonstrated in pilot experiments by examining the extent of

-12- DRAFT

APRIL 10, 1985

elimination of added host cell DNA. Such an analysis would provide the

theoretical extent of the removal of nucleic acid during purification.

Direct analyses of nucleic acid in several production lots

of the final product should be performed by hybridization analysis of

immobilized contaminating nucleic acid utilizing appropriate probes, such as

both nick-translated host cell and vector DNA. This method ought to provide

sensitivity on the order of 10 picograms per dose. Theoretical concerns

regarding transforming DNA derived from the cell substrate will be minimized

by the general reduction of contaminating nucleic acid.

4. Antigen Contamination

Products which are administered repeatedly or in large doses

should be assayed for trace antigenic constituents and product related

impurities (e.g. aggregates or degradation products) likely to contaminate the

final product. Tests such as Western blots, radioimmunoassays and enzyme-

linked immunosorbant assays using high affinity antibodies raised against the

product, host cell lysates, appropriate subcellular fractions, and culture

medium constituents, should be used to detect contaminating antigens. Because

the detection of antigens will be limited by the specificity and sensitivity

of the antisera used, these immunoassays will complement but not replace

silver stain analysis of SDS-PAGE gels. Patients given large or repeated

doses of a product should be monitored for the production of antibodies to

contaminating antigens.

5. Microbial Contamination

Appropriate tests should be conducted for microbial

contamination that demonstrate the absence of detectable bacteria (aerobes and

anaerobes), fungi, yeast and mycoplasma in the final product.

-13- DRAFT

APRIL 10, 1985

D. Preclinical Toxicity Evaluation

The specific preclinical testing needs are best addressed on a

case-by-case basis with the appropriate Office. Appropriate animal tests.

which might include those for carcinogenicity, teratogenicity and effects on

fertility may be necessary for a product in which the active ingredient is

radically altered from the natural substance.

VIII. Modified Protein Products

Using recombinant DNA procedures it may be possible to modify the

structure of proteins to enhance their desired biological properties and/or

diminish undesirable ones. Any substance that is not a natural constituent of

the human body may be antigenic and also may cause unknown and possibly

adverse biological effects. The use of such a product in humans depends on a

careful assessment of its new benefits compared to the risks identifiable

during its preclinical and clinical evaluation.

IX. Clinical Trials

Clinical trials will be necessary for products derived from recombinant

DNA technology to evaluate their safety and efficacy.

See "Points to Consider in the Characterization of Cell Lines Used to Produce

Biologicals." Office of Biologics Research and Review, Center for Drugs and

Biologics. FDA. (Federal Register, Vol. 49, N0. 110. June 6, 1984).

See "Points to Consider in the Manufacture of Injectable Monoclonal Antibody

Products Intended for Human Use In Vivo," Office of Biologics Research and

Review, Center for Drug and Biologics, FDA. (Federal Register, Vol. 49, p.

1138, January 9, 1984).

Hochstein. H.D., Elin, R.J., Cooper, J.F., Seligmann, Jr., E.R., and Wolff,

S.M. (1973). Bull. Parenteral Drug Assoc., 27, 139-148.

Dinarello. C.A., (1974) "Endogenous pyrogen" in Methods for Studying

Mononuclear Phagocytes, Adams. D., Edelsan, P., and Koren, H., Eds., pp. 629-

639, Academic Press.