Status: NDA approved in May 2012; EU approval denied (due to orphan exclusivity)

Cross ref.: See the Glucocerebrosidase, rDNA/Genzyme (Cerezyme) entry for general information regarding this enzyme.

Organizations involved:

Protalix BioTherapeutics Inc. – Manuf.; R&D; Tech.; Israel mark.

Pfizer, Inc. – World mark.

ICON Genetics GmbH – Tech.

Bayer Schering AG – Parent

WO 2005/080544, was filed in 2005, expiring in 2025, if granted. Description: Elelyso is a formulation of taliglucerase alfa , a beta-glucocerebrosidase enzyme glycoprotein, expressed by transformed carrot (Daucus carota subsp. sativus) cells using the ProCellEx proprietary expression system, using transformed carrot cells.

Taliglucerase alfa has a calculated molecular formulat of C2580H3918N880O727S17, disulfide bridges at 6-18 and 20-25, and glycosylation at sites Asn-21, Asn-61, Asn-148 and Asn-272.

Biological: The recombinant human beta-glucocerebrosidase expressed in carrot cell suspension culture naturally contains terminal mannose residues on its complex glycans, apparently as a result of the activity of a special vacuolar enzyme that modifies complex glycans. Hence, the plant-produced enzyme does not require exposure of mannose residues in vitro, which is a requirement for the production of Cerezyme. prGCD also displays a level of biological activity similar to that of Cerezyme produced in CHO cells, as well as a highly homologous high-resolution three-dimensional structure, determined by X-ray crystallography.

Unlike mammalian-expressed glycoprotein, plant-expressed beta-glucocerebrosidase naturally contains terminal mannose residues on its complex glycans, required for the enzyme to bind to mannose cellular receptors, apparently as as result of th activity of a plant cell enzyme that modifies complex glycans. Thus, plant-expressed enzyme does not require exposure of mannose residues in vitro, as required by Cerezyme.

rGCD expressed in carrot cells has a different glycosylation pattern than other beta-glucocerebrosidases. Preclinical and human clinical trials show that the in vivo half-life of prGCD is significantly longer than that of Cerezyme when measured and compared to publicly available data on Cerezyme.

Nomenclature: Glucocerebrosidase, rDNA/Protalix [BIO]; Elelyso [TR]; Uplyso [TR former]; taliglucerase alfa [USAN; INN]; beta-glucocerebrosidase, recombinant (carrot expressed) [SY]; prGCD [SY]; taliglucerase alfa [INN]; 37228-64-1 [CAS RN]; L-glutamyl-L-phenylalanyl-[495(497)-L-histidine(R>H)]human glucosylceramidase (beta-glucocerebrosidase) peptide with L-aspartyl-L-leucyl-L-leucyl-L-valyl-L-aspartyl-L-threonyl-L-methionine, glycosylated peptide 1-506 enzyme [CAS]

Companies.: prGCD was developed by Protalix BioTherapeutics. In Jan. 2008, Protalix leased a facilty in Carmiel, Israel, where it planned to substantially increase manufacturing capacity of prGCD.

In Dec. 2009 Pfizer exclusively licensed worldwide marketing rights excluding Israel, where Protalix has retained exclusive marketing rights. Pfizer paid Protalix $60 million licensing free. Pfizer and Protalix will share evenues and expenses relating to development of taliglucerase alfa on a 60:40 percent basis, respectively. Protalix can earn up to $155 million before sales.

Supply disruptions of approved glucocerebrosidase enzymes, notably Cerezyme, had been affecting those living with Gaucher disease since 2009 in multiple countries including the U.S. To help minimize the possibility of supply disruptions, Pfizer launched the "Supply Continuity Program," which endeavors to maintain a continuously restocked 24 months of supply at various stages of production for U.S. patients prescribed Elelyso.

Manufacture: Taliglucerase alfa has been developed using Protalix’ plant cell culture-based ProCellEx system for the expression and manufacture of recombinant proteins. ProCellEx platform is capable of producing proteins with an amino acid structure practically equivalent to that of the desired human protein and with very similar glycan structures.

Cell growth, from scale up through large-scale production, takes place in flexible, sterile, disposable, polyethylene suspension culture bioreactors (plastic bags) which are custom-designed and optimized for plant cell cultures and confined to a clean-room environment. Culture media is a simple mixture of sugar in water. Plant cell cultures are grown on aqueous media consisting of highly purified water and defined inorganic nutrients in a completely closed and controlled environment. Protalix's patented bioreactor system utilizes sterilized, large flexible plastic containers for culturing and harvesting cells in consecutive cycles, with a central unit providing oxygen and nutrients. The vials have been designed to allow for the removal of excess air and waste gases, as well as the introduction of inoculants and culture media.

The ProCellEx expression system is capable of producing proteins with an amino acid structure practically equivalent to that of the desired human protein, and with a very similar, although not identical, glycan, or sugar, structure. Proteins produced by the ProCellEx system maintain the biological activity of naturally-produced proteins.

Protalix asserts that the ProCellEx protein expression system produces recombinant proteins that exhibit consistent enzymatic activity from batch to batch, allowing prGCD to achieve its desired therapeutic effect more effectively than comparable proteins produced through mammalian cell-based expression systems due to its greater glycan efficacy and consistency.

Expressed protein is targeted to carrot cell storage vesciles using a plant-specific C-terminal cell sorting signal sequence.

A number of amino acid sequence alterations were required for plant expression. Ghe GCD signal peptide was replaced by that of Arabidopsis thaliana basic enchochitinase genel to facilitate co-translational translocation of the enzyme into the endoplasmic reticulum (ER). The storage vacuol targeting signal sequence from tobacco chitinase A was fused to the C-terminus to facilitate GCD targeting to the ER. Plant storage vescicles generally contain low levels of proteases. For further information, see "Production of Glucocerebrosidase with Terminal Mannose Glycans...," Plant Biotech. J., vol 5, p .579-90, 2007.

A major advantage Protalix holds is its ability to manufacture at a very low cost. Plant expression allows for cost-effective, large-scale production of recombinant proteins that are at least as safe as, if not safer than, traditional mammal cell proteins. An entire manufacturing facilty has been set up for a total outlay of roughly $10 million, a fraction of the $150 million -$1 billion estimated cost range for traditional mammalian cell-based biopharmaceutical manufacturing facilities. In addition, the cost per production run is a fraction (estimated at 15%-20%) of what it costs Genzyme to product Cerezyme or Shire to produce velaglucerase.

FDA class: Drug NDA

Status: Protalix expects to complete a rolling New Drug Application (NDA) with FDA in late 2009. Protalix has concluded a Special Protocol Assesment (SPA) agreement with FDA for the final design of the pivotal Phase III clinical trial for prGCD.

On Jan 13, 2010, the European Union (EU) Committee for Orphan Medicinal Products (COMP) of the European Medicines Agency (EMEA) recommended approval of the MAA for Uplyso, with orphan designation.

On Feb. 2, 2010, the NDA was filed. prGCD has received orphan status designation from FDA.

On Aug. 17, 2009, Protalix received approval for a treatment protocol (Treatment IND or expanded access protocol; NCT00962260) to FDA to make its glucocerebrosidase available in the U.S. [while Genzyme continues to have problems in the manufacture of imiglucerase (Cerezyme) and shortages of the enzyme persist]. This is an open-label expanded access trial of Uplyso in patients with Gaucher disease who require enzyme replacement therapy (ERT) and who have been treated with imiglucerase but for whom the dose has been reduced or discontinued due to shortage of the product. The treatment protocol allowed physicians and other care-providers to treat patients of Gaucher disease with Uplyso in the U.S. and additional countries world-wide while studies of Uplyso continue as part of the then ongoing pivotal Phase III trial. Prior to accepting the protocol, the FDA reviewed available data from the company’s on-going Phase III clinical development programs.

In Dec. 2009, Protalix filed a BLA seeking approval of Uplyso. The FDA granted Uplyso orphan product designation and fast track development status. Uplyso was developed under a Special Protocol Assessment (SPA). As of fall 2010, the Prescription Drug User Fee Act (PDUFA) action date was Feb. 25, 2011.

On Feb. 10, 2010, FDA sent a letter to Protalix requesting further information regarding the “chemistry, manufacturing and controls section of the NDA” Specifically, the agency’s request focused primarily on validation of the manufacturing process at Protalix’ upgraded facility. A validation plan for the Company's manufacturing process of taliglucerase alfa hadalready been established and reviewed by the FDA. Protalix anticipated submitting the requested data during the second quarter of 2010. While the NDA was still being evaluated, taliglucerase alfa continues being provided to Gaucher patients in the U.S. under an Expanded Access protocol, as well as to patients in the European Union, Israel and other countries under Named Patient provisions.

On Feb. 25, 2011, FDA issued a Complete Response Letter to Protalix. The main questions raised by the FDA regarding the NDA relate to clinical and chemistry, manufacturing and controls (CMC). In the clinical section, the FDA requested additional data from the Company's switchover trial and long-term extension trial. At the time the NDA was submitted, full data from these trials were not available. In the CMC section, the FDA requested information regarding testing specifications and assay validation. FDA did not request additional clinical studies. FDA had previously inspected the manufacturing facilities finding them acceptable. FDA also did not identify any issues in its audit of clinical sites.

On May 1, 2012, FDA approved Elelyso. The filin had designated Elelyso as a Fast Track drug. The time from submission to approval was 24.2 months, with the product undergoing 2 approval cycles and FDA somehow considering it having met the PDUFA date.

In June 2012 (just weeks after U.S. approval of Elelyso), EMA's Committee for Medicinal Products for Human Use recommended against EU approval of Elelyso in the EU, citing VPRIV as the reference product having orphan drug designation (10 years exclusivity) preventing approval of these similar products and that no shortage current exists. However, the committee gave Elelyso a positive risk-benefit assessment. Protalix/Pfizer had originally thought an exemption could be obtained for Elelyso because of the shortages of Cerezyme (which were resolved by the time the committtee ruling).

Tech. transfer: Protalix apparently licensed some plant cell expression technology from Icon Genetics GmbH, a subsidiary of Bayer Schering.

U.S. patents covering Elelyso include 7,951,557, "Human lysosomal proteins from plant cell culture ," assigned to Protalix, expires Feb. 24, 2024. This involves a "method for producing glycosylated proteins in plant culture, particularly proteins having a high mannose glycosylation, while targeting such proteins with an ER signal and/or by-passing the Golgi...for compositions and methods for the treatment of lysosomal storage diseases."

A related pending international filing, WO 2005/080544, was filed in 2005, expiring in 2025, if granted.

Trials: Because of the small number of affected patients, the efficacy of Elelyso (for FDA approval) was evaluated in a total of 56 patients with Type 1 Gaucher disease enrolled in two clinical trials. Many of these patients continued treatment in a longer-term extension study. Enrollment for the pivotal Phase III trial was completed in Dec. 2008, and the trial results reported completed in Fall 2009.

In Oct, 2009, Protalix reported positive results from its pivital Phase III trial with Uplyso in treatment naive patients diagnosed with Gaucher disease. The Phase III clinical trial for Uplyso was a nine month, randomized, double-blind, parallel group, dose-ranging safety and efficacy study in patients with Gaucher disease. Patients were randomized to receive either 60 units/kg or 30 units/kg of Uplyso administered intravenously once every two weeks. A total of 31 patients were enrolled at 11 centers in Europe, North America, South America, Israel and South Africa. The trial met its primary endpoint, mean reduction in spleen volume after nine months compared with baselines, in both 60 U/kg dose and in the lower 30 U/kg dose treatment groups (p <0.0001). The primary endpoint was stipulated in the Special Protocol Assessment (SPA) agreed on by the Company and FDA prior to the commencement of the trial. Additionally, the primary endpoint was observed already after six months of treatment in both treatment groups. Statistically significant improvements compared with baselines were observed in hemoglobin level and liver size and significant nominal elevation in platelet count in the lower dose of 30 U/kg. The safety analysis for both doses showed that Uplyso was well tolerated with no serious adverse events were reported. Only 6% of patients in the trial developed antibodies to Uplyso during the study. None of the patients in the trial developed neutralizing antibodies to UPLYSO. Only 6% of the patients in the trial experienced hypersensitivity.

The most common side effects reported during clinical studies were infusion reactions and allergic reactions. Symptoms of infusion reactions include headache, chest pain or discomfort, weakness, fatigue, hives, skin redness, increased blood pressure, back pain, joint pain, and flushing. As with other intravenous protein products, life-threatening allergic reactions have been observed in some patients during Elelyso infusions. Other commonly observed side effects observed in greater than 10% of patients included upper respiratory tract infection, common cold-like symptoms, joint pain, influenza, headache, extremity pain, back pain, and urinary tract infections.

Some have raised concerns regarding Uplyso, citing the 6% of patients in the trial who developed antibodies and experienced hypersensitivity reactions to Uplyso as something that could derail its approvals. However, none of the trial subjects have developed neutralizing levels of antibodies.

Market: Upon approval, Pfizer priced Elelyso 25% lower than Genzyme's Cerezyme. The Pfizer price was $150,000 annually versus the $200,000 annually for the market leader, Cerezyme. This is a rare example in which a biopharmaceutical launch has been priced significantly lower than the standard-of-care product. The $150.000/year price was also reported in Jan. 2013.

For patients with commercial insurance, Pfizer offers 100% co-pay assistance on Elelyso and financial assistance to the un- and under-insured. As is usual with high proced pharmaceuticals targeted at very small populations, Pfizer has a 24/7 help line offering reimbursement assistance, pharmacy support and other aid.

Ongoing: Through an agreement with Protalix, Yeda Research and Development Company Limited, the technology transfer arm of the Weizmann Institute of Science, is developing a next-generation enzyme for manufacture using ProCellEx.