bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 2082: Fc-FcγR interaction impacts the clearance and antitumor activity of antibody-drug conjugates in NSG mice
Authors: Li Fu , Ulrich Michelle , Hunter Joshua , Westendorf Lori , Olson Devra , Lee Cassie Baker , Benjamin Dennis , Law Che-Leung 
Published: July 2016

Abstract
Majority of preclinical efficacy studies for cancer therapeutics are performed on tumor models implanted in immune-deficient mouse strains, including athymic nude, severe combined immunodeficiency (SCID), or NOD-SCID/IL2Rgamma null (NSG) mice. To better understand the correlation between drug exposure and preclinical antitumor activity of biologics, we evaluated the pharmacokinetic (PK) profiles of antibodies and antibody-drug conjugates (ADC) in four strains of mice commonly used in cancer research, including BALB/c, athymic nude, SCID, and NSG. To our surprise, antibodies and ADCs had an abnormally short serum half-life in NSG mice, compared to other strains of mice.
We hypothesized that the fast clearance from plasma in NSG mice may reduce the overall exposure of xenografts to the ADCs, resulting in underestimation of antitumor activity. This was confirmed by comparing cAC10-vcMMAE in CD30+ Karpas-299 tumors implanted in either SCID mice or NSG mice. A single dose of 1 mg/kg cAC10-vcMMAE ADC resulted in complete remission of Karpas-299 tumors implanted in SCID mice (5/5). In contrast, the same treatment regimen had no effect on Karpas-299 tumors implanted in NSG mice (0/5). This observation suggests indeed the shortened exposure penalizes ADC efficacy in NSG models.
We then hypothesized that the fast clearance of ADCs from plasma in NSG mice could be mediated by Fc-FcγR interaction; compromising this interaction may improve the serum half-lives of antibodies and ADCs and thus enhance ADC-mediated antitumor effects in NSG mice. To test this, we utilized a mutant antibody with the amino acid substitutions of E233P:L234V:L235 in its Fc domain that result in significantly reduced FcγR binding (G1V1). These mutations restored the serum exposure in NSG mice to that level comparable to other strains of mice. As a result, treatment of 1 mg/kg cAC10G1V1-vcMMAE led to tumor remission in Karpas-299 tumors grown in NSG mice, correlating with extended exposure. In parallel, pretreatment with human IV immunoglobulin also enhanced ADC exposure and antitumor activity in the NSG mice.
In summary, these results suggest preclinical PK/PD assessment should be performed in the same strains of mice, especially when NSG xenograft models are used to evaluate activities. Moreover, reduced FcγR binding may enhance ADC exposure and allow a better assessment of therapeutic potential of biologics in NSG-based xenograft models.
Citation Format: Fu Li, Michelle Ulrich, Joshua Hunter, Lori Westendorf, Devra Olson, Cassie Baker Lee, Dennis Benjamin, Che-Leung Law. Fc-FcγR interaction impacts the clearance and antitumor activity of antibody-drug conjugates in NSG mice. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2082.
Abstract 2358: KHK2805, a novel ADCC- and CDC-enhanced anti-FOLR1 antibody with AccretaMab® technology, shows a potent anti-tumor activity in combination with pemetrexed
Authors: Ando Munetoshi , Nagata Keiko , Ishii Toshihiko , Nakai Ryuichiro , Takahashi Takeshi 
Published: July 2016

Abstract
Introduction: Folate receptor 1 (FOLR1, FR alpha) is a folate transporter which is expressed in many cancers including ovarian cancer (OvC) and non-small cell lung cancer (NSCLC), and which is an attractive target for cancer therapy, is currently the subject of ongoing studies. We established KHK2805, a novel anti-FOLR1 monoclonal antibody with AccretaMab® technology to enhance both the antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) activities. It was demonstrated that KHK2805 exhibits markedly high ADCC and CDC activity levels in clinical samples from ovarian cancer patients, while a tolerable safety profile has been observed in preclinical models using cynomolgus monkeys (100 mg/kg weekly for 4 weeks, intravenously). A greater understanding of the biology of FOLR1 is important for providing a novel therapeutic option for KHK2805 for patients with cancer. Pemetrexed (PEM), a second-generation anti-folate which inhibits thymidylate synthase, glycinamide ribonucleotide transformylase and dihydrofolate reductase, is used as a standard therapy for patients with cancers such as NSCLC. It is not fully understood how PEM treatment affects the expression of FOLR1 on cancer cells. We therefore examined the level of FOLR1 expression in cancer cells after PEM treatment, and the anti-tumor activity of KHK2805 in combination with PEM.
Materials and Methods: The FOLR1 expression levels after PEM treatment were examined in OvC, NSCLC, and endometrial cancer cells by flow cytometry. The ADCC activity of KHK2805 against PEM-treated cells was evaluated. The anti-tumor activity of KHK2805 in combination with PEM was investigated in SCID mice.
Results: Flow cytometry showed that PEM treatment increased the FOLR1 expression of various cancers such as OvC (IGROV1, SKOV3, MCAS), NSCLC (NCI-H1437, NCI-H2228), and endometrial cancer (MESSA, HEC1A, HEC1B) cells. In addition, PEM treatment enhanced the ADCC activity of KHK2805 against MCAS, NCI-H1437, and NCI-H2228, in comparison to cells that did not receive PEM treatment. Furthermore, the anti-tumor activity of KHK2805 in SCID mice bearing subcutaneous MCAS tumors was enhanced by PEM treatment.
Conclusions: PEM induced further FOLR1 expression in OvC, NSCLC, and endometrial cancer, resulting in the enhancement of the ADCC activity of KHK2805. The use of KHK2805 with PEM might therefore be a potent therapeutic option.
Citation Format: Munetoshi Ando, Keiko Nagata, Toshihiko Ishii, Ryuichiro Nakai, Takeshi Takahashi. KHK2805, a novel ADCC- and CDC-enhanced anti-FOLR1 antibody with AccretaMab® technology, shows a potent anti-tumor activity in combination with pemetrexed. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2358.
Abstract 2359: A-337, a potent bispecific antibody targeting EpCAM×CD3, as a potential immunotherapeutic agent for human solid tumors
Authors: Cui Yumin , Huang Zhihua , Chen Hanyang , Zhang Xinfeng , Qi Bo , Liu Heng , Yan Xiaoqiang 
Published: July 2016

Abstract
T cell bi-specific antibodies are potent molecules by binding and re-directing T cells to tumor cells through tumor associate antigens (TAAs), and triggering strong T cell activation and resulting in the killing of tumor cells. Bi-specific T cell engager antibody (BITE®) has demonstrated a remarkable clinical efficacy in liquid tumor. It remains to be a tremendous challenge for the development these types of bi-specific antibodies due to the induction of cytokine storm, thus limiting the dose-escalation in patients. A new immunotherapy antibody platform, (ITab TM), was developed to generate bi-specific antibody-like molecules. The molecules target TAA and activate human CD3 T cells simultaneously. A-337 is a bi-specific antibody targeting on EpCAM (Epithelial cell adhesion molecule) on tumor cells and CD3 in human T cells. In vitro, A-337 demonstrated high potency on activating human T cell measured by CD69 expression, and killing of EpCAM highly expressing tumor cell lines with EC50 values at &lt; 100 pM in the presence of human peripheral blood mononuclear cells (PBMC). The human PBMC dependent cell killing activity of A-337 was correlated to the expression levels of EpCAM on the surface of tumor cell lines. In the mouse model, A-337 showed dose-dependent growth inhibition of SW480 xenograft. In cynomolgus monkey studies, A-337 by single IV infusion induced peripheral T cell re-distribution or activation and cytokine release and showed favorable pharmacokinetics features. The current studies reveal that A-337 has potent anti-tumor activities in vitro and in vivo. These results demonstrate that A-337 is a promising and potent immunotherapeutic agent to treat EpCAM-expressing solid tumors and warrants further development.
Citation Format: Yumin Cui, Zhihua Huang, Hanyang Chen, Xinfeng Zhang, Bo Qi, Heng Liu, Xiaoqiang Yan. A-337, a potent bispecific antibody targeting EpCAM×CD3, as a potential immunotherapeutic agent for human solid tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2359.
Abstract 2376: Clonal evolution of skin carcinomas during tumor progression and metastasis
Authors: McCreery Melissa Q. , Balmain Allan 
Published: July 2016

Abstract
Tumor heterogeneity and the ongoing evolution of tumor subpopulations have presented considerable challenges to the success of cancer therapies, highlighting a critical need for greater understanding of these phenomena. We used a K5CreER-Confetti reporter mouse in combination with the DMBA (dimethylbenzanthracene)/TPA (12-O-tetradecanoylphorbol-13-acetate) skin carcinogenesis model to study the genetics, clonality, and evolutionary behavior of tumor subpopulations from tumor initiation to metastasis. Treating the skin of K5CreER-Confetti mice with tamoxifen results in widespread labeling of the epidermis and hair follicles, which persists for at least 18 months. Papillomas that develop from Confetti-activated skin are of clonal origin, evidenced by each tumor being distinctly dominated by a single Confetti color (RFP, YFP, GFP, or CFP; or uncolored). Twelve weeks after initiation, the majority of tumors remain single-colored, with only 22% (36 of 133) showing any evidence of a secondary color population present. By 20 weeks after initiation, however, nearly all tumors (78%, 42 of 54) have incorporated one or more secondary populations, readily identifiable as streaks of a distinct color. FACS separation and sequencing of these different colored populations reveals these populations are genetically distinct: in preliminary analysis, the primary color population typically carries the expected driver Hras Q61L mutation while the secondary populations do not. The tumor thus appears to be incorporating pseudo-normal tissue from its microenvironment during early growth. Activation of the Confetti reporter in tumors post-initiation in papillomas results in labeling of single cells with all 4 Confetti colors, allowing subpopulations and their evolution to be studied at later stages. These highly multi-color papillomas subsequently give rise to single-color carcinomas and metastases, suggesting that the conversion from a benign to malignant tumor is clonally driven. The Confetti mouse is a valuable tool for studying the clonality and genetics of subpopulations present in tumors, which need to be better understood in order to improve the treatment of heterogeneous human tumors.
Citation Format: Melissa Q. McCreery, Allan Balmain. Clonal evolution of skin carcinomas during tumor progression and metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2376.
Abstract 2743: Finding determinants of PARP inhibitor sensitivity using genome-wide and focused CRISPR screens
Authors: Pettitt Stephen , Krastev Dragomir B. , Song Feifei , Ashworth Alan , Lord Christopher J. 
Published: July 2016

Abstract
We are using genomic approaches to study the mechanism of action of targeted cancer drugs, particularly poly(ADP-ribose) polymerase (PARP) inhibitors. One of these drugs, olaparib was recently approved for use in ovarian cancers with germline BRCA1/2 mutations and many other clinical trials with this and other PARP inhibitors are underway. Experimental study of potential resistance mechanisms can inform the ongoing clinical development of these drugs.
We previously carried out a loss of function mutagenesis screen in haploid cells, which showed that PARP1 was required for cellular toxicity of olaparib and other PARP inhibitors. This supported the hypothesis that PARP inhibitor toxicity occurs via a poisoning mechanism where inhibited PARP is tightly bound to DNA, forming a toxic lesion.
Recently we carried out a similar screen using genome-wide lentiviral CRISPR-Cas9 mutagenesis in diploid cells. Many PARP inhibitor resistant clones had loss of function Parp1 mutations as expected. However, we also isolated a point mutation affecting a single amino acid in the Parp1 DNA binding domain. This mutant encodes a stable Parp1 protein that cannot bind DNA and does not become trapped in the presence of inhibitors. Thus the CRISPR screen implicated PARP1 DNA binding directly in determination of PARP inhibitor toxicity and was extremely informative about the mechanism of action compared to conventional loss-of-function mutagenesis.
We extended this approach by synthesising a high-density focused sgRNA library targeting only PARP1. We developed a reporter cell line that allows us to selectively isolate in-frame mutations that preserve PARP1 protein expression. By deep sequencing mutagenised and appropriately selected cells we identified a series of subtle mutations in PARP1 that result in PARP inhibitor resistance, giving us a detailed insight into structure-function relationships in PARP1. The approach is applicable to other drug targets, providing a framework for understanding drug action and predicting clinical resistance.
Citation Format: Stephen Pettitt, Dragomir B. Krastev, Feifei Song, Alan Ashworth, Christopher J. Lord. Finding determinants of PARP inhibitor sensitivity using genome-wide and focused CRISPR screens. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2743.
Abstract 290: NF1 loss modulates cellular fitness in KIT-mutant gastrointestinal stromal tumor (GIST)
Authors: Marino-Enriquez Adrian , Li Bin , Bahri Nacef , Lauria Alexandra , Wang Yuexiang , Fletcher Jonathan A. 
Published: July 2016

Abstract
Patients with inoperable GIST obtain substantial clinical benefit from imatinib and other KIT/PDGFRA inhibitors. However, secondary resistance develops in 90% of patients within 18-24 months. Reactivation of oncogenic signaling pathways at time of progression is most often due to secondary mutation in KIT or PDGFRA, but downstream RAS or BRAF mutations are occasionally alternative mechanisms of KIT/PDGFRA-inhibitor resistance.
We identified deleterious NF1 mutations in 3 KIT-mutant GIST samples from patients progressing on imatinib. In genomic scale loss-of-function shRNA genomic screens, designed to identify genes involved in imatinib resistance, a shRNA targeting NF1 was the most enriched shRNA in imatinib-treated GIST cells out of 54,000 shRNAs (NF1 gene score 29/11,238). To evaluate the contribution of NF1 loss to KIT-mutant GIST resistance, NF1-deficient GIST models were generated from 2 patient-derived, KIT-mutant GIST cell lines, GIST882 and GIST-T1, by sequential cotransfection with Cas9 and 2 independent NF1-targeting CRISPR-sgRNAs.
Complete loss of NF1 protein was observed after 5-10 passages due to on-target heterogeneous genomic deletion at the NF1 locus. Orthogonal validations were obtained using stable shRNA-mediated NF1 knockdown with similar results in the same GIST cell lines. NF1-deleted cells retained expression of mutant KIT but were resistant to imatinib (IC50 196 and 500nM, significantly increased from baseline 34 and 110nM, for GIST-T1 and GIST882, respectively). Notably, after interruption of imatinib treatment, NF1-deficient GIST cells showed reduced proliferation (69% and 77% growth reduction at day 7 off imatinib, for GIST-T1 and GIST882, t test p&lt;0.001) despite continuous expression of activated KIT and downstream signaling effectors.
In conclusion, acquired NF1 loss induces TKI resistance in KIT-mutant GIST cells but results in reduced cellular fitness in the absence of KIT-inhibitor treatment. These findings suggest that NF1-deficient GIST subclones that expand on imatinib treatment can be destabilized by intermittently discontinuing KIT-inhibitor therapy.
Citation Format: Adrian Marino-Enriquez, Bin Li, Nacef Bahri, Alexandra Lauria, Yuexiang Wang, Jonathan A. Fletcher. NF1 loss modulates cellular fitness in KIT-mutant gastrointestinal stromal tumor (GIST). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 290.
Abstract 2925: Anti-tumor activity of a MYC-targeting dicer substrate siRNA in combination with BRD4/CDK7 inhibitors
Authors: Chipumuro Edmond , Siddiquee Zakir , Ganesh Shanthi , Shui Serena , Shah Anee , Kim Boyoung , Chen Dongyu , Pandya Purva , Storr Rachel , Wang Weimin , Dudek Hank , Lai Cheng , Abrams Marc , Brown Bob 
Published: July 2016

Abstract
MYC is a well-characterized driver of numerous tumor types. Since the protein encoded by this gene is challenging to target via conventional modalities, progress in new therapeutic agents has been slow despite decades of research. RNA interference technology has enabled the inhibition of previously-undruggable genetic targets at the mRNA level, and has advanced to clinical development for several indications. DCR-MYC, a lipid nanoparticle (LNP)-formulated Dicer substrate siRNA (DsiRNA) targeting MYC mRNA, is currently in Phase Ib/II clinical trials and showing promising results. In this study we used an improved EnCore LNP and MYC DsiRNA, which demonstrated MYC mRNA silencing activity and efficacy in mouse models of human hepatocellular carcinoma (HCC). Small molecule inhibitors that target BRD4; JQ1 and CDK7; THZ1 has previously reported anti-proliferative effects in various cancer types and efficacy in several tumor mouse models including HCC. Treatment with both JQ1 and THZ1 induced cell cycle arrest and apoptosis in various cancer cells by repressing MYC expression. Here we observed striking anti-proliferative effects in vitro when MYC-DsiRNA was combined with THZ1 in cancer cells. In addition, when mice bearing HCC tumors were treated with MYC-DsiRNA combined with either THZ1 or JQ1, the antitumor efficacy was additive or synergistic relative to either single agent alone. We observed significantly more MYC mRNA knockdown in the tumors that had the combination treatment compared to the tumors that received either of the single agent treatment. These preclinical data suggests the possibility of a significant and practical benefit of combining MYC-DsiRNA and small molecule inhibitors that target an epigenetic regulator BRD4 (JQ1) and a global gene regulator CDK7 (THZ1).
Citation Format: Edmond Chipumuro, Zakir Siddiquee, Shanthi Ganesh, Serena Shui, Anee Shah, Boyoung Kim, Dongyu Chen, Purva Pandya, Rachel Storr, Weimin Wang, Hank Dudek, Cheng Lai, Marc Abrams, Bob Brown. Anti-tumor activity of a MYC-targeting dicer substrate siRNA in combination with BRD4/CDK7 inhibitors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2925.
Abstract 2965: In vitro and in vivo activity of a site-specific SeriMab antibody-drug conjugate (ADC) using an indolino-benzodiazepine DNA-alkylating agent
Authors: Vitharana Dilrukshi , Wilhelm Alan , Harris Luke , Archer Katie , Shizuka Manami , Maloney Erin , Ab Olga , Laleau Rassol , Sun Xiuxia , Pinkas Jan , Miller Michael , Chari Ravi , Keating Thomas , Fishkin Nathan 
Published: July 2016

Abstract
Previously we have described the characterization of a proprietary class of indolino-benzodiazepine dimers, IGNs, with high potency against many cancer lines. Antibody-drug conjugates (ADCs) made with mono-imine containing IGNs were designed to only alkylate DNA and not cause DNA crosslinking. ADCs with the IGN linked via lysine residues of the antibody were shown to be highly potent and antigen specific. Here we apply our SeriMab site-specific technology platform, which employs N-terminal conjugatable aldehydes derived from oxidation of a serine residue, to link an IGN molecule to the antibody using a peptide linker. This ADC (SeriMab-IGN-P1) has exactly 2 IGN molecules per antibody conjugated to the N-termini of the heavy chains, as determined by MS analysis.
Serimab-IGN-P1 was found to maintain binding to the target antigen with comparable affinity to the unconjugated antibody by FACS analysis (Kd = 300 pM). The conjugate was highly potent (IC50 = 4 pM) against a cancer cell line with high target expression (3 × 106 antibodies bound per cell) as well as a cell line with much lower target expression (2 × 104 antibodies bound per cell, IC50 = 22 pM). SeriMab-IGN-P1 also demonstrated strong bystander killing activity against proximal target-negative cancer cells, likely due to a cell permeable metabolite identified in cells expressing the target antigen.
The unique oxime linkage in SeriMab-IGN-P1 was found to be stable in circulation in mice for 3 days, as determined by affinity capture LC-MS; the conjugate species with 2 IGNs per antibody remained predominant over this period with an estimated t1/2 of &gt;10 days for payload release.
In vivo, SeriMab-IGN-P1 was found to be effective against human lung cancer xenografts (NCI-H2110), with anti-tumor activity observed at single doses as low as 2 μg/kg (payload dose), and complete responses observed at 5 μg/kg. This conjugate was also well tolerated in CD-1 mice at doses significantly higher than the minimum effective dose that produced tumor regression.
These data are highly encouraging for new ADC therapies using the SeriMab site-specific conjugation platform with potent DNA-acting payloads.
Citation Format: Dilrukshi Vitharana, Alan Wilhelm, Luke Harris, Katie Archer, Manami Shizuka, Erin Maloney, Olga Ab, Rassol Laleau, Xiuxia Sun, Jan Pinkas, Michael Miller, Ravi Chari, Thomas Keating, Nathan Fishkin. In vitro and in vivo activity of a site-specific SeriMab antibody-drug conjugate (ADC) using an indolino-benzodiazepine DNA-alkylating agent. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2965.