Biopharmaceuticals: Approval Trends in 2005

August 1, 2006
Gary Walsh, PhD

Associate Professor in the Industrial Biochemistry Program at the University of Limerick. He is also a member of BioPharm International's Editorial Advisory Board.

BioPharm International, BioPharm International-08-01-2006, Volume 19, Issue 8

In 2005, 10 biopharma- ceuticals gained marketing approval in the US or Europe, although only five of them were genuinely new molecular entities.

To date, about 165 biopharmaceuticals have gained marketing approval in the United States or Europe; approximately one in every four drugs introduced on the market is a biopharmaceutical.1 The term "biopharmaceutical," as used here, refers to recombinant therapeutic proteins, monoclonal antibodies used for therapeutic or in vivo diagnostic purposes, or nucleic acid-based products.

The global annual sales value of these products is about $33 billion, with recombinant erythropoietin (EPO) sales alone reaching $10.7 billion last year. Sales values of nonantibody-based therapeutic proteins are forecast to reach $52 billion by 2010,2 while sales values of therapeutic monoclonals will likely reach $16.7 billion by 2008.3 The biopharmaceutical market should approach or surpass $70 billion by the end of this decade.

In 2005, 10 biopharmaceuticals won approval in the United States or Europe. These were six hormones and growth factors, two antibody-based products, and two therapeutic enzymes (Table 1). Compared with previous approvals, this profile was somewhat out of the ordinary; there were no additional blood factors, anticoagulants, thrombolytics, interferons, interleukins, or recombinant vaccines. The profile of associated target indications also was atypical; for example, only one product (Avastin) was indicated for the treatment of cancer.

Quick Recap

Only five of the 10 approvals are genuinely new molecular entities. Levemir and Kepivance, and Xolair and Avastin, although approved in Europe last year, gained approval before 2005 in some other world regions. The active biotech ingredient of GEM 21S, on the other hand, is identical to the active ingredient in Regranex, a product approved in 1997. In terms of expression systems used, four of the approved biopharmaceuticals are produced in mammalian cell lines and in Escherichia coli (E. coli). Two are produced in engineered Saccharomyces cerevisiae (S. cerevisiae), again confirming that these three expression systems are the workhorses of the biopharmaceutical industry.

Table 1. Biopharmaceuticals (defined as recombinant proteins, monoclonal antibody and nucleic acid-based products) approved in the United States or European Union in 2005.

In 2005, there were notable approvals of nonparenteral delivery systems and biosimiliars. Until last year, all approved biopharmaceuticals required to enter the bloodstream were administered parenterally. Parenteral drug administration, however, often results in reduced patient compliance and potential complications when in nonclinical settings. Fortical (Table 1) is the first biologic product delivered systemically by an alternative (intranasal) means. Nasal delivery is attractive because it is convenient. Also, the presence of high-density blood vessels, along with nasal microvilli, generates a large potential absorption surface area. Peptides and smaller proteins are often absorbed intranasally with acceptable bioavailabilities. Larger molecules—with a molecular mass greater than 10 kDa—are poorly absorbed through nasal membranes, so this approach is less attractive for many biopharmaceuticals.

In 2005, Omnitrope (a recombinant hGH produced by Sandoz (Princeton, NJ) became the first biosimiliar product to be approved in Australia, and this year won approval in both Europe and the US.

Last year had its downside, to be sure. Tysabri was abruptly withdrawn in February after only four months on the market for patent safety issues. In June 2006 it was reintroduced under altered, more limited indications.

The remainder of this article provides detailed information about the products approved in 2005. Data was gathered from regulatory sources,4,5 as well as the web sites of sponsoring companies. Details about Levemir, Kepivance, and Avastin were included in the May 2005 issue of BioPharm International,6 so are not repeated below.

BIOPHARMACEUTICALS APPROVED IN 2005

Fortical (calcitonin-salmon, recombinant) is a 32-amino-acid, single- chain, polypeptide hormone produced by recombinant means in E. coli. It gained approval in the US in 2005 for the treatment of postmenopausal osteoporosis. Calcitonin is secreted by the parafollicular cells of the thyroid gland in mammals and by the ultimobranchial gland of birds and fish. The hormone increases the amount of calcium and phosphate in bones and also reduces serum calcium levels.

Salmon calcitonin is 30 times more potent in humans when compared with the endogenous human hormone, hence its application in medicine. Chemically synthesized calcitonin of both human and salmon sequence has been used for over 20 years and recombinant salmon calcitonin (Forcaltonin) was approved in the EU in 1999 for the treatment of the bone disorder Paget's disease. After fermentation of the producer microorganism, Fortical is chromatographically purified and formulated with citric acid, sodium chloride, phenylethyl and benzyl alcohol, and polysorbate as excipients. It is presented as a metered dose solution (3.7 mL), with an associated pumping mechanism for nasal delivery. A single spray delivers 200 IU calcitonin activity in a volume of 0.09 mL. The recommended dosage schedule is one intranasal spray daily. Mean product bioavailability is 3% (with a range of 0.3–30% reported), and absorption through the nasal mucosa is rapid.

Postmenopausal osteoporosis is characterized by low bone mass and increased bone fragility, caused by a disproportionate rate of bone reabsorption, compared with bone formation. Consequently, there is an increased risk of fracture, particularly of the vertebrae, hip, and distal forearm. Calcitonin inhibits the bone reabsorption process. Intranasally administered product increases spinal bone mass in postmenopausal women with established osteoporosis as demonstrated by two randomized placebo controlled trials involving 325 women. Adverse reactions were generally mild to moderate, with nasal-related problems, such as irritation and soreness most commonly reported. Fortical is manufactured by Unigene Laboratories and distributed by Upsher-Smith Laboratories (Maple Grove, MN).

GEM 21S (growth-factor-enhanced matrix), approved by FDA last year, is classified as a medical device. It consists of two components, tricalcium phosphate and recombinant human platelet-derived growth factor-BB (rhPDGF-BB). It is indicated for the treatment of specific defects of the tissue supporting the teeth (periodontal defects).

The product is supplied as a kit consisting of a cup containing 0.5 mL of tricalcium phosphate and a syringe containing 0.5 mL of rhPDGF-BB (0.3 mg/mL). The two constituents are aseptically mixed immediately before use, allowed to stand for 10 minutes, and directly applied to the damaged area. The tricalcium phosphate generates a sponge-like porous scaffold for the PDGF, provides a framework for bone ingrowth, and helps stabilize the surrounding soft tissue. The PDGF exerts potent mitogenic and chemotactic effects on bone and periodontal ligament-derived cells, thereby accelerating periodontal healing.

Native human PDGF is a dimer, with two constituent polypeptides identified (A and B) and three active isoforms: AA, AB, and BB. The BB isoform is glycosylated, with the two 109-amino-acid polypeptides held together by interchain disulphide bonds. The product is produced in engineered S. cerevisiae, followed by multistep chromatographic purification. The same active ingredient (but formulated as a gel and applied topically) has been on the market since the late 1990s under the tradename Regranex, for the treatment of diabetic ulcers.

Initial animal studies show that PDGF promotes the regeneration of periodontal tissues including bone, cementium, and periodontal ligament. The safety and efficacy of GEM 21S in humans were primarily demonstrated via a multicenter, double-blinded, randomized, controlled, prospective clinical trial involving 180 patients who required surgical intervention to treat periodontal defects.

Efficacy was monitored using clinical attachment-level measurements and radiographic bone measurements over a six-month period, with significantly increased endpoint values reported for the GEM 21S group. No serious adverse events attributable to the product were reported, although standard events associated with periodontal grafting procedures (e.g., pain, swelling, and bleeding) were noted. GEM 21S is manufactured by BioMimetic Pharmaceuticals (Franklin, TN) and is distributed by Osteohealth, a division of Luitpold Pharmaceuticals (both in Shirley, NY).

Hylenex (hyaluronidase recombinant human), as its generic name suggests, is a purified preparation of recombinant human hyaluronidase. It is a 447-amino-acid glycoprotein of approximate molecular mass 61 kDa. The FDA approved it in 2005 as an adjuvant to increase the absorption and dispersion of other injected drugs, as well as for hypodermoclysis (subcutaneous-based fluid replacement) and as an adjuvant in subcutaneous urography for improving resorption of radiopaque agents.

Hyaluronidases are enzymes that degrade hyaluronan, a high-molecular mass, linear-structural polysaccharide consisting of repeating disaccharide units of D-glucuronic acid linked to N-acetyl D glucosamine. The enzyme is widely distributed in the extracellular matrix, vitreous humor, cartilage, and several other tissues of higher animals. Subcutaneous administration of hyaluronidase increases the permeability of the local connective tissue via hyaluronan degradation.

The enzyme therefore can act as a spreading agent, facilitating more rapid diffusion of subcutaneously coadministered fluids or localized transudates or exudates, facilitating their more rapid systemic absorption. Bovine and ovine hyaluronidase directly extracted from native tissue traditionally has been used for cosmetic and pharmaceutical purposes in orthopedics, ophthalmology, and general medicine.

The advent of bovine spongiform encephalitis has all but halted commercial use of the bovine enzyme. Production via recombinant means largely overcomes potential accidental pathogen transmission. Upstream processing entails cell culture of the producer CHO cell line with multistep chromatographic purification after initial product recovery. Final product is formulated as a solution for subcutaneious administration. It contains 150 USP units of recombinant enzyme/mL, sodium chloride, sodium phosphate buffer components, human serum albumin, calcium chloride, and edentate disodium as excipients.

Enhanced absorption and distribution of drugs are usually achieved by subcutaneous coadministration of 150 IU hyaluronidase activity. The most frequently reported adverse reactions occur at the local injection site and sometimes allergic reactions occur. Hylenex is manufactured by Baxter Healthcare Corporation (Deerfield, IL) and distributed by Baxter and Halozyme Therapeutics (San Diego, CA).

Increlex (mecasermin) is a recombinant form of human insulin-like growth factor-1 (rhIGF-1) produced in E. coli. The 7.6 kDa, 70-amino-acid, single-chain polypeptide displays an amino acid sequence identical to that of the native human growth factor. It is characterized by the presence of three intrachain disulphide linkages. The product was approved for general medical use by the FDA last year and is indicated for the long-term treatment of growth failure in children with primary IGF-1 deficiency or growth hormone (GH) gene deletion who have developed neutralizing antibodies to GH (see also IPLEX entry below).

IGF, as its name suggests, bears a strong structural resemblance to proinsulin. IGF-1 is synthesized primarily in the liver, and then released into the bloodstream. Its cell surface receptors are found on a wide variety of cell types in the body. Transcription of the IGF-1 gene is strongly initiated when GH binds to its hepatic receptor, and most of the growth-promoting effects of GH are actually mediated by IGF-1. Direct injection of IGF-1 into animals whose pituitary gland (and hence source of GH) have been removed stimulated longitudinal bone growth, as well as growth of various organs, including the kidneys, spleen, and thymus.

Increlex manufacture is initiated by fermentation of the producer E. coli cells. After initial product recovery, it is subject to a number of high resolution chromatographic steps. Excipients added are sodium acetate buffer components, sodium chloride benzyl alcohol, and polysorbate 20. After filter sterilization, the product (10 mg/mL active) is aseptically filled into multidose glass vials (40 mg active/vial).

Increlex is generally administered twice daily by subcutaneous injection at a starting dose of 40–80μg/kg. Long-term product dosage levels are individualized for each patient. Bioavailability following subcutaneous administration is close to 100% and mean terminal serum half life in pediatric patients is estimated at 5.8 hours.

Product safety and efficacy were assessed by a total of five clinical studies conducted in 71 pediatric patients, with treatment supporting mean height velocities (cm growth per year) ranging from 2.8–8.0 over several years. Adverse events included hypoglycemia. The product is contraindicated in the presence of active or suspected neoplasia, because of the potential stimulatory effect on cancer cell growth. Increlex is manufactured by Baxter and distributed by Tercica (Brisbane, CA).

IPLEX (mecasermin rinfabate) contains a protein complex of rhIGF-1 and rhIGF-binding protein 3 (rhIGFBP-3), both of which are produced in (separate) E. coli strains. rhIGF-1 is a single-chain, 70-amino-acid polypeptide (see Increlex entry). RhIGFBP-3 is a single-chain, 264-amino-acid, 28.7 kDa polypeptide containing 18 cysteine residues, all of which participate in disulphide bond formation. Both recombinant polypeptides present in IPLEX display amino acid sequences identical to the native human proteins. Naturally occurring IGFBP-3 is glycosylated, while the recombinant version is devoid of this post-translational modification, a consequence of expression in E. coli. When mixed together, the two molecules form a 1:1 molar ratio complex of overall molecular mass 36.4 kDa. The product gained approval in the US in 2005 and is indicated for the treatment of growth failure in children with primary IGF-1 deficiency or with GH gene deletion who have developed neutralizing antibodies to GH.

As described in the context of Increlex, most of the growth-promoting effects of GH are actually mediated by IGF-1. The growth factor promotes linear growth, as well as additional anabolic effects. In serum, IGF is invariably complexed to an IFGBP, of which there are six (IGFBP-1 to IGFBP-6). Individual IGFBPs display differing amino acid sequences and molecular masses, although they generally exhibit in the region of 50% homology to each other. The bulk of serum IGF-1 is found as an equimolar (1:1:1) complex, with IGFBP-3 and an acid-labile polypeptide. IGFBPs most likely fulfill several biological functions, including stabilization and protection of IGF-1 from proteolysis in the serum, increasing serum half-life, and modulating IGF-1 function locally at the surface of IGF-1 sensitive cells. This includes modulating their potential to induce hypoglycemia. Free IGF-1 can interact with the insulin receptor, although relatively weakly, and it consequently displays about 5% of the hypoglycemic potential of insulin.

Product manufacture entails separate fermentation and purification procedures of both recombinant proteins. After mixing, the final product is formulated to a concentration of 36 mg/0.6 mL filled in a single-use glass vial. The final product contains sodium acetate buffer components and sodium chloride as excipients.

Pharmacokinetic studies indicate that the mean serum half-life of IGF-1 when complexed to its binding protein is 13 hours, which supports its once daily subcutaneous administration. Exact dosage levels may be individualized for each patient but starting doses are typically 0.5 mg/kg, increased to 1–2 mg/kg.

Product approval was largely granted based on results from a single, open-label, multicenter study in 36 prepubertal subjects. Eighty-nine percent (32 subjects) had primary GH receptor deficiency (Laron syndrome), while three individuals (8%) had GH gene deletion with neutralizing antibodies to GH. After six months of treatment, annualized height velocity (cm/year) was almost doubled (from 3.4 to 7.4) upon treatment with 1 mg product/kg daily, while treatment with 2 mg/kg daily increased annualized height velocity levels to a mean of 8.8 cm. Adverse reactions sometimes associated with the product include hypoglycemia and lymphoid tissue hypertrophy. The product is contraindicated in the presence of active or suspected neoplasia. IPLEX is manufactured and marketed by Insmed (Glen Allen, VA).

Naglazyme (galsulfase) is a recombinant version of the human enzyme N-acetylgalactosamine 4-sulfatase produced by an engineered CHO cell line. The 495-amino-acid, 56 kDa enzyme, also contains six asparagine-linked (N-linked) glycosylation sites, carrying a mixture of complex high-mannose and phosphorylated high-mannose oligosaccharides. A second, post-translational modification characteristic of the enzyme is the conversion (within the endoplasmic reticulum of producing cells) of cysteine 53 into a formylglycine residue. This modification is essential for catalytic activity.

Naglazyme, which holds orphan status, was approved in the US in 2005 (and subsequently in Europe this year) for the treatment of patients with the lysosomal storage disease, mucopolysaccharidosis VI (MPS). This rare genetic defect, with an estimated 1100 cases in the developed world, is characterized by the absence of lysosomal N-acetylgalactosamine 4-sulfatase. The enzyme normally participates in the degradation of the glycosaminoglycan dermatan sulphate (a sugar polymer), and in affected individuals it accumulates in the lysosomes. Accumulation ultimately causes multiple medical complications, including skeletal deformity, joint disease, and cardiopulmonary disease. Until the approval of Naglazyme, there had been no satisfactory treatment available for MPS. Naglazyme therapy is essentially an enzyme replacement therapy. Cellular and, subsequently, lysosomal entry from the blood are likely mediated by the binding of the enzyme's bisphosphorylated oligomannose, oligosaccharide side chains, to cell- surface, mannose-6-phosphate receptors. This triggers endocytotic uptake. The product is provided as a concentrated solution (1 mg/mL enzyme) administered by infusion once a week. Immediately before use, the product is diluted with saline to 250 mL, which is infused over a four-hour period.

Product manufacture entails initial cell culture of the CHO producer strain with subsequent purification from the extracellular culture media. Initial harvest involves filtration, followed by an ultrafiltration-based concentration step. Purification is based on three, high-resolution chromatographic steps. Specific filtration, as well as incubation at low pH steps, are undertaken to inactivate any virus potentially present. Phosphate buffer constituents and polysorbate 80 are added as excipients.

Clinical efficacy was assessed in three studies, in which a total of 56 MPS patients were enrolled. Primary endpoints measured were based on physical endurance tests. Product administration resulted in improved 12-minute walk distance and three-minute stairs climbing tests. Administration also resulted in decreased urinary glycosaminoglycan (GAG) levels. The most common serious adverse events noted were infusion related. Additional adverse events included headache, fever, and upper respiratory tract infections. Virtually all patients administered Naglazyme develop antibodies against the product within the first few weeks of treatment, although the long- term significance of this, if any, remains to be determined. Naglazyme is manufactured and distributed by BioMarin Pharmaceuticals (Novato, CA).

Xolair (omalizumab) is an engineered (humanized) IgG antibody that specifically binds to human immunoglobulin E (IgE). The 149 kDa, glycosylated antibody is produced by an engineered CHO cell line. The product was approved in the EU in 2005, although it has been available in the US since 2003. It is indicated as an add-on treatment for asthma in individuals 12 years and older.

Allergic asthma is a chronic condition of the respiratory tract, usually treated with inhaled corticosteroids and beta agonists. The condition is underpinned by over expression of IgE in response to environmental allergens, such as pollen or dust mites. Allergen-specific IgE in turn binds to high affinity (FcεR1) receptors on airway-associated effector cells, including mast cells and basophils. Binding triggers release of histamine, prostaglandins, leukotrienes and cytokine-based proinflammatory mediators, thereby triggering a characteristic asthma attack.

Xolair brings about its intended effect by binding to the IgE, thereby inhibiting their interaction with the FcεR1 receptors. Dosage regimes typically entail subtaneous administration of 15–375 mg product every two to four weeks. The product is absorbed slowly from the site of injection, reaching peak serum concentrations after seven or eight days.

The product is manufactured via initial cell culture in batch fed suspension mode. Purification is achieved using a combination of protein A affinity chromatography, followed by both cation exchange and anion exchange chromatographic steps. Chromatography is followed by product concentration (ultrafiltration) and diafiltration. Sucrose, histidine, and polysorbate 20 are used as excipients and the final filter-sterilized product is lyophilized in single-use vials containing either 75 or 150 mg active ingredient.

Clinical safety and efficacy were determined mainly by five double-blind, placebo-controlled studies involving over 2,000 patients. In most trials, the number of asthma exacerbations per patient was significantly reduced by Xolair treatment. Exacerbations were defined as a worsening of asthma requiring either systemic corticosteroid administration, or a doubling of inhaled corticosteroid treatment levels. The most serious adverse reactions recorded were anaphylaxis and an increased malignancy rate (from 0.2 to 0.5% of patients). Additional adverse reactions included injection site reactions, headache, and an increased incidence of viral infection. Xolair is manufactured by Genentech (South San Francisco, CA) and is marketed by Genentech and Novartis (East Hanover, NJ).

Gary Walsh, PhD, senior lecturer, industrial biochemistry program, University of Limerick, Limerick City, Ireland, Tel. 353. 61. 202664, Fax 353.61.202568 Gary.walsh@ul.ie

REFERENCES

1 Walsh G. Biopharmaceutical benchmarks. Nature biotechnol. In press

2 Pavlou AK, Reichert JM. Recombinant protein therapeutics—success rates, market trends and values to 2010. Nature biotechnol. 2004;22:1513-19.

3 Pavlou A, Belsey, M. The therapeutic antibody market to 2008. Eur. J. Pharm. Biopharm. 2005; 59:389-396.

4 www.fda.gov

5 www.emea.eu.int

6 Walsh G. Biopharmaceuticals: approvals and approval trends in 2004. Biopharm Int.2005;18 (5):58-65.