Orthogonal Cysteine Protection Enables Homogeneous Multi-Drug Antibody-Drug Conjugates

A strategy for the preparation of homogeneous antibody–drug conjugates (ADCs) containing multiple payloads has been developed. This approach utilizes sequential unmasking of cysteine residues with orthogonal protection to enable site‐specific conjugation of each drug. In addition, because the approach utilizes conjugation to native antibody cysteine residues, it is widely applicable and enables high drug loading for improved ADC potency. To highlight the benefits of ADC dual drug delivery, this strategy was applied to the preparation of ADCs containing two classes of auristatin drug‐linkers that have differing physiochemical properties and exert complementary anti‐cancer activities. Dual‐auristatin ADCs imparted activity in cell line and xenograft models that are refractory to ADCs comprised of the individual auristatin components. This work presents a facile method for construction of potent dual‐drug ADCs and demonstrates how delivery of multiple cytotoxic warheads can lead to improved ADC activities. Lastly, we anticipate that the conditions utilized herein for orthogonal cysteine unmasking are not restricted to ADCs and can be broadly utilized for site‐specific protein modification.

The Methylene Alkoxy Carbamate Self-Immolative Unit: Utilization for the Targeted Delivery of Alcohol-Containing Payloads with Antibody-Drug Conjugates

A strategy for the conjugation of alcohol-containing payloads to antibodies has been developed and involves the methylene alkoxy carbamate (MAC) self-immolative unit. A series of MAC β-glucuronide model constructs were prepared to evaluate stability and enzymatic release, and the results demonstrated high stability at physiological pH in a substitution-dependent manner. All the MAC model compounds efficiently released alcohol drug surrogates under the action of β-glucuronidase. To assess the MAC technology for ADCs, the potent microtubule-disrupting agent auristatin E (AE) was incorporated through the norephedrine alcohol. Conjugation of the MAC β-glucuronide AE drug linker to the anti-CD30 antibody cAC10, and an IgG control antibody, gave potent and immunologically specific activities in vitro and in vivo. These studies validate the MAC self-immolative unit for alcohol-containing payloads within ADCs, a class that has not been widely exploited.

Development of Novel Quaternary Ammonium Linkers for Antibody-Drug Conjugates

A quaternary ammonium-based drug-linker has been developed to expand the scope of antibody-drug conjugate (ADC) payloads to include tertiary amines, a functional group commonly present in biologically active compounds. The linker strategy was exemplified with a β-glucuronidase-cleavable auristatin E construct. The drug-linker was found to efficiently release free auristatin E (AE) in the presence of β-glucuronidase and provide ADCs that were highly stable in plasma. Anti-CD30 conjugates comprised of the glucuronide-AE linker were potent and immunologically specific in vitro and in vivo, displaying pharmacologic properties comparable with a carbamate-linked glucuronide-monomethylauristatin E control. The quaternary ammonium linker was then applied to a tubulysin antimitotic drug that contained an N-terminal tertiary amine that was important for activity. A glucuronide-tubulysin quaternary ammonium linker was synthesized and evaluated as an ADC payload, in which the resulting conjugates were found to be potent and immunologically specific in vitro, and displayed a high level of activity in a Hodgkin lymphoma xenograft. Furthermore, the results were superior to those obtained with a related tubulysin derivative containing a secondary amine N-terminus for conjugation using previously known linker technology. The quaternary ammonium linker represents a significant advance in linker technology, enabling stable conjugation of payloads with tertiary amine residues. Mol Cancer Ther; 15(5); 938-45. ©2016 AACR.

Novel Auristatins with High Bystander and Cytotoxic Activities in Drug Efflux-positive Tumor Models

Auristatins, a class of clinically validated anti-tubulin agents utilized as payloads in antibody-drug conjugates, are generally classified by their membrane permeability and the extent of cytotoxic bystander activity on neighboring cells after targeted delivery. The drugs typically fall within two categories: membrane permeable monomethyl auristatin E-type molecules with high bystander activities and susceptibility to efflux pumps, or charged and less permeable monomethyl auristatin F (MMAF) analogs with low bystander activities and resistance to efflux pumps. Herein, we report the development of novel auristatins that combine the attributes of each class by having both bystander activity and cytotoxicity on multidrug-resistant (MDR⁺) cell lines. Structure-based design focused on the hydrophobic functionalization of the N-terminal N-methylvaline of the MMAF scaffold to increase cell permeability. The resulting structure-activity relationships of the new auristatins demonstrate that optimization of hydrophobicity and structure can lead to highly active free drugs and antibody-drug conjugates with in vivo bystander activities.

Development of Novel Antibody-Camptothecin Conjugates

We have developed a highly active and well-tolerated camptothecin (CPT) drug-linker designed for antibody-mediated drug delivery in which the lead molecule consists of a 7-aminomethyl-10,11-methylenedioxy CPT (CPT1) derivative payload attached to a novel hydrophilic protease-cleavable valine-lysine-glycine tripeptide linker. A defined polyethylene glycol stretcher was included to improve the properties of the drug-linker, facilitating high antibody-drug conjugate (ADC) drug loading, while reducing the propensity for aggregation. A CPT1 ADC with 8 drug-linkers/mAb displayed a pharmacokinetic profile coincident with parental unconjugated antibody and had high serum stability. The ADCs were broadly active against cancer cells in vitro and in mouse xenograft models, giving tumor regressions and complete responses at low (≤3 mg/kg, single administration) doses. Pronounced activities were obtained in both solid and hematologic tumor models and in models of bystander killing activity and multidrug resistance. Payload release studies demonstrated that two CPTs, CPT1 and the corresponding glycine analog (CPT2), were released from a cAC10 ADC by tumor cells. An ADC containing this drug-linker was well tolerated in rats at 60 mg/kg, given weekly four times. Thus, ADCs comprised of this valine-lysine-glycine linker with CPT drug payloads have promise in targeted drug delivery.

Proapoptotic signaling activity of the anti-CD40 monoclonal antibody dacetuzumab circumvents multiple oncogenic transformation events and chemosensitizes NHL cells

Non-Hodgkin lymphoma (NHL) is a genetically heterogeneous disease with several oncogenic events implicated in the transformation of normal developing B lymphocytes. The objective of this study was to elucidate the signal transduction-based antitumor mechanism(s) of action for the anti-CD40 monoclonal antibody dacetuzumab (SGN-40) in NHL. We report that dacetuzumab activates two distinct proapoptotic signaling pathways, overcoming transformation events key to the pathogenesis of NHL. Dacetuzumab-mediated CD40 signaling constitutively activated the nuclear factor-κB and mitogen-activated protein kinase signaling pathways producing the sustained downregulation of B-cell lymphoma 6 (BCL-6), an oncoprotein implicated in lymphomagenesis. Loss of BCL-6 resulted in c-Myc downregulation and activation of a transcriptional program characteristic of early B-cell maturation, concomitant with reduced proliferation and cell death. In a second mechanism, dacetuzumab signaling induced the expression of the proapoptotic p53 family member TAp63α and downstream proteins associated with the intrinsic and extrinsic apoptotic machinery. Dacetuzumab was synergistic in combination with DNA-damaging chemotherapeutic drugs, correlating with TAp63α upregulation. Furthermore, dacetuzumab augmented the activity of rituximab in combination with multiple chemotherapies in the xenograft models of NHL. The ability of dacetuzumab signaling to circumvent oncogenic events and potentiate the activity of chemotherapy regimens provides a unique therapeutic approach to NHL.

Abstract 3694: Relationship between in vivo antitumor activity of ADC and payload release in preclinical models

Antibody-drug conjugates (ADC) deliver cytotoxic payloads to target cells via receptor-mediated internalization. We have demonstrated that SGN-35 (cAC10-vcMMAE) binds to CD30 on target cells and releases intracellular monomethyl auristatin E (MMAE) in vitro, contributing to potent killing of CD30+ cells. Using a set of auristatin-based ADCs, we evaluated whether the intratumoral concentration of the released payload is a predictive indicator of antitumor activity in preclinical models.

We first treated CD30+, anaplastic large cell lymphoma (ALCL) Karpas 299 tumors with SGN-35 or a non-binding control ADC (IgG-vcMMAE). The plasma ADC and MMAE PK measurements were similar in SGN-35 and IgG-vcMMAE treated tumor-bearing animals. In contrast, SGN-35 generated 5-fold greater intratumoral MMAE exposure than IgG-vcMMAE, which correlated with tumor regression observed in the SGN-35- treated group.

We then examined the relationship between released MMAE and in vitro cytotoxicity by targeting different receptors expressed on the same cells. The lymphoma cell line L82 expresses CD30, CD70, and CD71 receptors. Although auristatin-based ADCs targeting each of these targets has a different IC50, the intracellular MMAE was similar when 50% growth inhibition was achieved (approximately 200 nM). In vivo, CD30, CD70, or CD71-directed ADCs demonstrated similar antitumor activity for a given dose level (0.5, 1, or 3 mg/kg). Concordantly, equal intratumoral MMAE concentrations were observed for a given dose level, regardless of the antigen target.

The cell permeable MMAE has been shown to mediate bystander killing in vitro. To evaluate whether intratumoral MMAE mediates bystander killing in vivo, an admixed tumor model consisting CD30+ and CD30- Karpas 299 cells was treated with SGN-35. As predicted, both CD30+ and CD30- tumor cells were killed, presumably due to intratumoral diffusion of MMAE across cell membranes. In contrast, a conjugate with a highly polar form of auristatin (MMAF) was unable to kill the CD30-negative cell population of the admixed tumors.

These preclinical results provide evidence that the concentration of released MMAE within the tumor correlates with the ADC antitumor activity in vitro and in vivo. Moreover, the in vivo bystander activity of MMAE may improve utility of this chemotype in tumors with heterogeneous antigen expression.

Citation Format: Fu Li, Xinqun Zhang, Kim Emmerton, Mechthild Jonas, Jocelyn Setter, Bill Arthur, Nicole Okeley, Robert Lyon, Dennis Benjamin, Che-Leung Law. Relationship between in vivo antitumor activity of ADC and payload release in preclinical models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3694. doi:10.1158/1538-7445.AM2014-3694

Improving Antibody-Tubulysin Conjugates through Linker Chemistry and Site-Specific Conjugation

Tubulysins have emerged in recent years as a compelling drug class for delivery to tumor cells via antibodies. The ability of this drug class to exert bystander activity while retaining potency against multidrug-resistant cell lines differentiates them from other microtubule-disrupting agents. Tubulysin M, a synthetic analogue, has proven to be active and well tolerated as an antibody-drug conjugate (ADC) payload, but has the liability of being susceptible to acetate hydrolysis at the C11 position, leading to attenuated potency. In this work, we examine the ability of the drug-linker and conjugation site to preserve acetate stability. Our findings show that, in contrast to a more conventional protease-cleavable dipeptide linker, the β-glucuronidase-cleavable glucuronide linker protects against acetate hydrolysis and improves ADC activity in vivo. In addition, site-specific conjugation can positively impact both acetate stability and in vivo activity. Together, these findings provide the basis for a highly optimized delivery strategy for tubulysin M.

Abstract 982: Development of homogeneous dual-drug ADCs: Application to the co-delivery of auristatin payloads with complementary antitumor activities

A common theme in treating cancer is the use of combination chemotherapy, where multiple drugs with different mechanisms of action are combined to elicit synergistic activity or overcome differential drug sensitivities. Antibody-drug conjugates (ADCs) have emerged as a powerful approach for treating cancer, combining the tumor targeting specificity of monoclonal antibodies with the potent cell-killing activity of cytotoxic drugs. Like other therapies, these agents are increasingly being tested in combination with unconjugated, clinically approved anticancer agents. In addition, emerging data demonstrates that insensitivity to a particular ADC can be overcome through delivery of a different payload using the same antibody. For these reasons, the development of ADCs that can deliver two complementary payloads to a tumor would likely be a significant advancement in ADC technology. To enable dual-drug conjugation, we utilized a multiplexing drug carrier that contains cysteine residues with orthogonal protecting groups and identified novel conditions for utilization of these protecting groups on a folded protein. Sequential cysteine unmasking enables discrimination between conjugation sites to allow for site-specific drug conjugation. This strategy provides homogeneous ADCs bearing 16 total drugs per antibody, split evenly between the two drug linkers. Importantly, this strategy is flexible, as it does not require engineered antibodies or custom enzymes for drug-linker conjugation. To demonstrate the potential benefits of ADC dual drug delivery, this strategy was applied to the construction of ADCs bearing two classes of auristatin drug linkers that have different physiochemical properties and complementary anti-cancer activities. Dual-auristatin ADCs were tested in cell line and xenograft models that have differential sensitivities to the individual auristatin components, including those with heterogeneous antigen expression or high levels of drug efflux transporters. The data from these studies demonstrate that the dual-auristatin ADCs were active on cells and tumors that are refractory to treatment with either of the individual component drugs. This work highlights the potential for delivering two synergistic or complementary payloads on a single ADC and presents a flexible method for constructing dual-drug ADCs with site-specific and homogeneous drug loading.

Citation Format: Matthew R. Levengood, Xinqun Zhang, Kim K. Emmerton, Joshua H. Hunter, Peter D. Senter. Development of homogeneous dual-drug ADCs: Application to the co-delivery of auristatin payloads with complementary antitumor activities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 982. doi:10.1158/1538-7445.AM2017-982

Abstract 56: Antibody-drug conjugates containing glucuronide-tubulysin payloads display activity in MDR+ and heterogeneous tumor models

While antibody-drug conjugates (ADCs) find increasing application in cancer treatment regimens, de novo or treatment-emergent resistance mechanisms could impair clinical benefit. Two resistance mechanisms that emerge under continuous ADC exposure in vitro include upregulation of transporters that confer multidrug resistance (MDR+) and loss of cognate antigen expression. New technologies that circumvent these resistance mechanisms may serve to extend the utility of next generation ADCs. Recently, we developed the quaternary ammonium linker system to expand the scope of conjugatable payloads to include tertiary amine-containing compounds and applied the linker to tubulysins, a highly potent class of microtubule disrupting agents that maintain activity in MDR+ cell lines. Quaternary ammonium-linked glucuronide-tubulysin drug-linkers were synthesized and evaluated as ADCs. The resulting conjugates were potent and immunologically specific across a panel of cancer cell lines, including those displaying the MDR phenotype. The ADCs also demonstrate potent bystander activity in a co-culture model containing a mixture of antigen-positive and -negative cell lines. Incorporation of a PEG12 side chain in the linker enabled loading at 8-drugs/Ab for increased in vivo potency while maintaining suitable ADC pharmacokinetic properties. In vivo, the glucuronide-tubulysin conjugates displayed activity in MDR+ xenograft models and bystander activity in an admixed Ag+/Ag- heterogeneous tumor model. Thus, the glucuronide-tubulysin drug-linkers represent a promising new payload for ADCs, combining conjugate potency in the presence of the MDR phenotype with robust activity in models of tumor antigen heterogeneity.

Citation Format: Patrick J. Burke, Joseph Z. Hamilton, Joshua H. Hunter, Julia H. Cochran, Thomas A. Pires, Christopher I. Leiske, Kim K. Emmerton, Peter D. Senter, Robert P. Lyon, Scott C. Jeffrey. Antibody-drug conjugates containing glucuronide-tubulysin payloads display activity in MDR+ and heterogeneous tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 56. doi:10.1158/1538-7445.AM2017-56

Abstract 2885: Discovery of a tripeptide-based camptothecin drug-linker for antibody-drug conjugates with potent antitumor activity and a broad therapeutic window

In efforts to bring forward antibody-drug conjugate (ADC) technologies that complement vedotin and enable new clinical-stage ADCs, we have investigated compounds that interact with topoisomerase 1, an enzyme involved in the unwinding of DNA. In connection with this, we developed a highly active and well-tolerated camptothecin drug-linker technology, in which the lead molecule consists of 7-aminomethyl-10,11-methylenedioxycamptothecin (AMDCPT) attached to a protease-cleavable valine-lysine-glycine (VKG) tripeptide linker unit. A hydrophilic and discrete polyethylene glycol unit was included to improve the properties of the drug-linker, enabling high ADC drug-loading, and reducing the propensity for aggregation. A VKG-AMDCPT ADC, with 8 drug-linkers/mAb (DAR8), displayed a pharmacokinetic profile coincident with parental unconjugated antibody, with a high degree of stability against retro-Michael reaction deconjugation. ADCs based on the VKG-AMDCPT were broadly active against cancer cells in vitro, and in mouse xenograft models, giving tumor regressions and complete responses with a single ≤3 mg/kg dose. These included both solid and hematologic tumor models, and models of bystander killing activity and multidrug resistance. A non-binding DAR8 ADC was well-tolerated in rats at 60 mg/kg, q7dx4. The VKG-AMDCPT drug-linker can be prepared from available materials in eight high-yielding steps, and this drug-linker is being employed in the anti-CD30 ADC, SGN-CD30C; an investigational new drug application is planned for 2020.

Citation Format: Ryan Lyski, Lauren Bou, Margo Zaval, Kim Emmerton, Nicole Okeley, Jessica Simmons, Francisco Zapata, David Ortiz, Erica McKinney, David Meyer, Maureen Ryan, Peter Senter, Scott Jeffrey. Discovery of a tripeptide-based camptothecin drug-linker for antibody-drug conjugates with potent antitumor activity and a broad therapeutic window [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2885.

Abstract 1649: Impact of linker and conjugation site on tubulysin M ADC stability and in vivo activity

The tubulysins are a potent class of microtubule-disrupting agents consisting of natural products and designed analogues that have become a compelling cytotoxic payload for drug-targeting applications. This is due in large part to their high cytotoxic potency on cancer cells, including those that express transporters conferring the multidrug resistance (MDR+) phenotype. All potent tubulysin natural products contain an acetoxy group at the C11-position in the central tubuvaline residue. Deacetylation results in >100-fold loss of cellular and biochemical potency, underscoring the importance of this structural element. Recently, we developed quaternary ammonium linker systems to conjugate tertiary amine-containing payloads, and applied them to the tubulysins. In this work, protease- and β-glucuronidase-cleavable quaternary ammonium linkers of tubulysin M were evaluated as ADC payloads. In vitro, both dipeptide and glucuronide linker systems provided ADCs with comparable biologic properties. However, in vivo, linker chemistry and conjugation site were important parameters impacting acetate group stability. Higher degrees of stability translated to greater activity in xenograft models. ADCs were prepared with both dipeptide and glucuronide linkers as heterogeneous ADCs loaded at an average of 4-drugs/Ab (DAR 4), and as homogeneous ADCs loaded at 2-drugs/Ab (DAR 2) at the engineered S239C sites. Increased in vivo acetate stability was observed for glucuronide-based conjugates relative to the dipeptide analogue. Further stabilization was achieved by conjugating at the S239C sites (DAR 2) relative to native antibody cysteines (DAR 4). Tubulysin M acetate stabilization by both linker and conjugation site selection resulted in increased ADC potency in preclinical models and, combined, serves as an enabling strategy for antibody-mediated tubulysin M drug delivery.

Citation Format: Patrick J. Burke, Joseph Z. Hamilton, Thomas A. Pires, Christopher I. Leiske, Julia H. Cochran, Jocelyn R. Setter, Kim K. Emmerton, Andrew B. Waight, Peter D. Senter, Robert P. Lyon, Scott C. Jeffrey. Impact of linker and conjugation site on tubulysin M ADC stability and in vivo activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1649.

Abstract 2803: Novel auristatins with high activity on efflux-positive models and demonstrable bystander activity

Auristatins are a class of clinically validated antimitotic agents utilized as payloads in antibody-drug conjugates (ADCs). Auristatins display many of the desirable properties necessary for ADC cytotoxins, such as low nanomolar potency, cell permeability, and activity across multidrug-resistant (MDR+) cell lines. Herein, we report the development of novel auristatins, which have a unique combination of these favorable properties. The hydrophilic monomethyl auristatin F (MMAF) was chosen as the parent structure, and a medicinal chemistry campaign was undertaken to functionalize various sites of the auristatin with hydrophobic moieties in an effort to improve membrane permeability. The structure-activity relationships (SAR) of the new auristatins demonstrated clear trends correlating hydrophobicity, structure, and polarity with permeability and in vitro cytotoxicity. The highest-performing molecules showed a preference for hydrophobic functionalization at the N-terminal dolavaline. The payloads were linked to the C-terminal position of the auristatin with a lysosomally cleavable maleimido-dipeptide linker. Examination of the ADCs revealed low ng/mL activity in CD30+ and CD19+ cell lines in vitro. Anti-CD70 ADCs demonstrated high in vivo efficacy in a 786-O xenograft and complete remissions (CRs) in the efflux-positive renal cell carcinoma model. Anti-CD30 ADCs were dosed in a CD30+ and CD30- admixed Karpas/Karpas-35R xenograft model to demonstrate proof-of-concept in vivo bystander activity. In summary, these novel auristatins showed potential across multiple indications as ADC payloads.

Citation Format: Philip N. Moquist, Tim D. Bovee, Andrew B. Waight, Sarah Owen, Jamie A. Mitchell, Margo Zaval, Marsha Quick, Sharsti Sandall, Kim K. Emmerton, Nicole Blesie, Robert P. Lyon, Peter Senter, Svetlana Doronina. Novel auristatins with high activity on efflux-positive models and demonstrable bystander activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2803.

Abstract A097: Tubulysin ADC payloads: An antimitotic drug class that retains activity in multidrug resistant models

As antibody-drug conjugates (ADCs) find increasing clinical application, treatment-related resistance mechanisms may eventually impact efficacy. One resistance mechanism that emerges following prolonged exposure to auristatin-based ADCs such as brentuximab vedotin and polatuzumab vedotin involves upregulation of efflux pumps that confer the multidrug resistance positive (MDR+) phenotype. New payload technologies that retain activity in this context may be important for next-generation anti-tubulin ADCs. The tubulysins are a potent class of tubulin binders consisting of natural products and designed analogues which have become a compelling cytotoxic payload for drug targeting applications. This is due in large part to their high cytotoxic potency on cancer cells, including those that express MDR-conferring transporters. Recently, we developed the quaternary ammonium linker system to conjugate tertiary amine-containing payloads and applied it to the tubulysins. In this work, β-glucuronidase-cleavable quaternary ammonium linkers of tubulysin M were evaluated as ADC payloads for activity in MDR+ models. The resulting conjugates displayed high potency in multiple MDR+ models at well-tolerated doses, including those resistant to MMAE-based ADCs. In addition to potency in resistant models, the tubulysin conjugates also retained bystander activity - a property in common with vedotin-based conjugates and important for indications characterized by heterogeneous antigen expression. Thus, the glucuronide-tubulysin M linker could enable future ADC programs designed for the treatment of resistant tumors due to emergence of MDR transporters.

Citation Format: Patrick J Burke, Joseph Z Hamilton, Thomas A Pires, Kim K Emmerton, Peter D Senter, Scott C Jeffrey. Tubulysin ADC payloads: An antimitotic drug class that retains activity in multidrug resistant models [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A097. doi:10.1158/1535-7163.TARG-19-A097

Abstract C52: Enhancing the activities of endogenous antibodies

Many monoclonal antibodies (mAbs) exhibit activity through antibody dependent cellular cytotoxicity (ADCC), due to the binding interactions between the Fc portion of the mAb and Fc RIIIa on natural killer cells, macrophages and neutrophils. The strength of this interaction is affected by the glycosylation pattern at Asn-297 on mAb heavy chains. Defucosylated mAbs and mAbs with bisecting N-acetylglucosamine carbohydrates bind to Fc RIIIa with higher affinities, have more pronounced ADCC activities, and have demonstrated promising in vitro and in vivo activities. We have described a novel method for generating such mAbs involving the addition of simple fucose derivatives to the culture media of antibody-producing cell lines. This leads to the production of defucosylated mAbs with significantly (20–50 fold) increased ADCC activities, while minimally impacting production and cell viability. Generation of sugar engineered antibodies in this manner is distinguished from other technologies in that there is no need for genetic engineering and cell line modification. In addition, the technology has unique in vivo applications for endogenous production of defucosylated antibodies with high affinity binding to mouse Fc receptors. Here, we show for the first time that immunocompetent mice generate defucosylated antibodies when orally administered fucose derivatives such as fluorofucose. There were no apparent toxicities associated with treatment with fluorofucose at doses that led to greater than 90% defucosylation of circulating antibodies, Applications for these novel findings will be discussed.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C52.