Partnering in Antibody Drug Conjugates

Antibody drug conjugates (ADCs) represent a niche but important area in biotherapeutic drug development. ADCs, which consist of a monoclonal antibody (mAb) chemically linked to a small-molecule therapeutic, are a promising modality for certain therapeutic areas such as oncology. ADCs are attracting the interest of both small and large pharmaceutical companies in their drug-development efforts as well as contract manufacturers specializing in high-potency API manufacturing and related conjugation services.

Patricia Van Arnum

Evaluating the opportunities

In August 2011, FDA approved Adcetris (brentuximab vedotin), codeveloped by Seattle Genetics and Millennium Pharmaceuticals (now part of Takeda Pharmaceutical), making it only the second ADC approved by FDA. Adcetris was approved for treating Hodgkin's lymphoma and systemic anaplastic large-cell lymphoma. Adcetris consists of three parts: the chimeric IgG1 antibody cAC10, specific for human CD30, the microtubule-disrupting agent monomethyl auristatin E (MMAE), and a protease-cleavable linker that covalently attaches MMAE to cAC10 (1, 2). Before the approval of Adcetris, the only other ADC approved by FDA was Mylotarg (gemtuzumab ozogamicin), approved more than 10 years ago in 2000. The drug, an anti-CD33 mAb conjugated to the cytotoxin calicheamicin, was developed by Wyeth (now part of Pfizer) and was granted accelerated approval in 2000 but was voluntarily withdrawn by Pfizer in 2010 because a required Phase III trial failed to demonstrate a survival advantage for Mylotarg plus chemotherapy compared with chemotherapy alone (1).

Other ADCs are advancing. Roche's Trastuzumab emtansine (T-DM1) is an ADC in Phase III development. The drug combines trastuzumab, (Herceptin), which targets human epidermal growth factor receptor 2 (HER2) receptors in breast and stomach cancer, with a maytansine derivative DM1, a small-molecule cytotoxin that binds to tubulin to prevent microtubule formation, through a nonreducible bis-maleimido-trixyethylene glycol linker (1, 2). Trastuzumab was developed by Genentech (now part of Roche) and was approved by FDA in 1998 for use in women with metastatic breast cancer who have tumors that overexpress the HER2 protein. The maytansine derivative DM1 and linking technology were developed by ImmunoGen (1). Genentech submitted a biologics license application for trastuzumab emtansine to FDA for use in people with HER2-positive, unresectable locally advanced or metastatic breast cancer, and Roche submitted a marketing authorization application to EMA for the same indication. Roche presented data showing encouraging efficacy, safety and quality of life results for T–DM1 at the American Society of Clinical Oncology annual conference in June 2012. Roche has a total of nine ADCs in its development pipeline. It includes RG7593, a humanized IgG1 anti-CD22 monoclonal antibody (anti-CD22) conjugated to an antimitotic agent in Phase I development.

ISTOCKPHOTO/THINKSTOCK IMAGES

Pfizer also is advancing ADCs. Its lead ADC product is inotuzumab ozogamicin, consisting of a mAb targeting CD22, a cell-surface antigen expressed on approximately 90% of B-cell malignancies, linked to a cytotoxic agent. As of March 2011, Pfizer had 10 ADC programs in preclinical development (3).

In October 2012, the biotechnology company Seattle Genetics expanded its ADC collaboration with Abbott. Under the expanded deal, Abbott will pay an upfront fee of $25 million for rights to use Seattle Genetics' auristatin-based ADC technology with antibodies to additional oncology targets. Seattle Genetics's proprietary technology uses synthetic cytotoxic agents, such as monomethyl auristatin E (MMAE) and monomethyl auristatin F (MMAF), and stable linker systems that attach these cytotoxic agents to the antibody. In addition in its deal with Abbott, Seattle Genetics may receive up to $220 million in potential milestone payments per additional target upon achieving predetermined development and commercial objectives as well as mid-to-high single-digit royalties on worldwide net sales of any resulting products under the multitarget collaboration. Seattle also is partnered with Genentech for ADC development and with Takeda for Adcetris.

Other companies specializing in ADC technology are partnering with pharmaceutical companies. Earlier this year, Spirogen announced a multiyear collaboration and license agreement with Genentech for the discovery and development of ADCs using Spirogen's pyrrolobenzodiazepine-based drugs and associated linker technology. Spirogen will be primarily responsible for synthesizing and manufacturing drug reagents while Genentech will use Spirogen's drug reagents to generate ADCs and evaluate their potential therapeutic utility. Genentech will have the exclusive license to fully develop and commercialize licensed products that contain these ADCs.

Mersana Therapeutics, which is developing ADCs using its Fleximer polymer and customizable linker chemistries, formed a $270-million collaboration with Endo Pharmaceuticals in March 2012. The Fleximer polymer is customized to improve the pharmacokinetics of targeting moieties, such as antibody fragments, and also to optimize the quantity of cytotoxic payload carried per targeted conjugate and the stability of the drug–polymer linkage as well as the targeting moiety–polymer linkage. In July 2012, Mersana received $27 million in venture-capital funding, which included investment by Pfizer Venture Investments.

Biotecnol and PolyTherics formed a collaboration last month for the development of multispecific tribody drug conjugates (TDCs). The companies will combine Biotecnol's tribody technology with PolyTherics' proprietary site-specific linker technologies to attach cytotoxic payloads to various tribodies for targeted cancer therapy. Tribody molecules are multispecific antibody products that, from a single molecule, enable the targeting of two or three tumor antigens in the same disease or two or three epitopes on the same tumor target. In vitro and in vivo studies conducted by Biotecnol have demonstrated tribodies to have targeting abilities and high tumor-to-blood ratios, which make them suitable for delivering toxic payloads in certain disease settings. Biotecnol has a portfolio of multivalent antibodies and capabilities in antibody development and antibody engineering, which will be directed toward this collaboration.

PolyTherics' ThioBridge linker technology is a conjugation technology for creating more stable, less heterogeneous ADCs through site-specific linkage and rebridging of disulfide bonds. It has been developed to support the conjugation of a range of therapeutic payloads to antibodies, antibody fragments, or scaffolds through specific sites without impacting functional domains. The companies will test the potency of the ThioBridge tribody-drug conjugates in preclinical cancer models.

Contract manufacturers expand

Contract API manufacturers offering high-potency manufacturing and related conjugation services are expanding their offerings in response to increase demand for ADCs and other highly potent compounds. For example, Carbogen Amcis and ADC Biotechnology recently announced a partnership to provide customers with development and manufacturing services for ADCs. ADC Bio will provide access to proprietary solid-phase immobilization technologies for conjugation and long-term storage of ADCs, and Carbogen Amcis will focus on small- to large-scale GMP supply and on the formulation of ADCs.

In October 2012, Fujifilm Diosynth Biotechnologies formed a strategic alliance with Piramal for ADC production whereby the two parties will offer contract development and manufacture of ADCs. Piramal offers ADC production at its site in Grangemouth, Scotland. Fujifilm recently announced an expansion of its cGMP manufacturing facilities at its sites in Research Triangle Park, North Carolina, and Billingham, United Kingdom.

Novasep recently announced an EUR 3 million ($3.9 million) invesment to expand its highly potent API (HPAPI) manufacturing capabilities at its Le Mans, France, facility. The plant expansion is expected to be fully operational by the beginning of 2013. The new Le Mans facility adds to Novasep's strategy for total synthesis of ADCs, including toxin and mAb production, mAb-toxin coupling, downstream processing, and formulation.

Lonza recently partnered with the biopharmaceutical company Intellect Neurosciences to provide the future development and manufacture of Intellect's ADC Conjumab-A. Lonza will supply the preclinical study material for the drug optimization and drug selection for Intellect's Conjumab-A. The new program includes in vitro and in vivo studies to evaluate both therapeutic and prophylactic potential in age-related macular degeneration testing different chemical variants manufactured by Lonza.

Patricia Van Arnum is executive editor of Pharmaceutical Technology, 485 Route One South, Bldg F, First Floor, Iselin, NJ 08830 tel. 732.346.3072, pvanarnum@advanstar.com Twitter@PharmTechVArnum.

References

1. A. Ritter, Pharm. Technol. 36 (1), 42–47 (2012).

2. FDA, "Label for Adcetris, BLA 125338," FDA Approved Drug Products: Drugs@FDA, accessed Dec. 20, 2011.

3. M. Dolsten, presentation at the Barclay 2011 Global Healthcare Conference, Mar. 17, 2011.