Clinical Pharmacology of the Antibody-Drug Conjugate Enfortumab Vedotin in Advanced Urothelial Carcinoma and Other Malignant Solid Tumors

Enfortumab vedotin is an antibody-drug conjugate comprised of a human monoclonal antibody directed to Nectin-4 and monomethyl auristatin E (MMAE), a microtubule-disrupting agent. The objectives of this review are to summarize the clinical pharmacology of enfortumab vedotin monotherapy and demonstrate that the appropriate dose has been selected for clinical use. Pharmacokinetics (PK) of enfortumab vedotin (antibody-drug conjugate and total antibody) and free MMAE were evaluated in five clinical trials of patients with locally advanced or metastatic urothelial carcinoma (n = 748). Intravenous enfortumab vedotin 0.5-1.25 mg/kg on days 1, 8, and 15 of a 28-day cycle showed linear, dose-proportional PK. No significant differences in exposure or safety of enfortumab vedotin and free MMAE were observed in mild, moderate, or severe renal impairment versus normal renal function. Patients with mildly impaired versus normal hepatic function had a 37% increase in area under the concentration-time curve (0-28 days), a 31% increase in maximum concentration of free MMAE, and a similar adverse event profile. No clinically significant PK differences were observed based on race/ethnicity with weight-based dosing, and no clinically meaningful QT prolongation was observed. Concomitant use with dual P-glycoprotein and strong cytochrome P450 3A4 inhibitors may increase MMAE exposure and the risk of adverse events. Approximately 3% of patients developed antitherapeutic antibodies against enfortumab vedotin 1.25 mg/kg. These findings support enfortumab vedotin 1.25 mg/kg monotherapy on days 1, 8, and 15 of a 28-day cycle. No dose adjustments are required for patients with renal impairment or mild hepatic impairment, or by race/ethnicity.

Prevalence of claudin 18.2 (CLDN18.2) and the association of biomarkers with clinical activity in patients with gastric or gastroesophageal adenocarcinoma (G/GEJa) treated with zolbetuximab

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Background: CLDN18.2, a targetable biomarker, is a tight junction protein normally confined to gastric mucosa of healthy tissue and often retained in G/GEJa. Zolbetuximab, a chimeric IgG1 monoclonal antibody, binds to CLDN18.2 and mediates cancer cell death via antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). Phase 2 FAST study results showed prolonged survival with zolbetuximab+EOX (epirubicin, oxaliplatin, capecitabine) vs EOX in CLDN18.2-positive G/GEJa. In ILUSTRO Cohort 2, confirmed partial responses (PRs) and stable disease (SD) were previously reported in 63.2% and 10.5%, respectively, of patients (pts) treated with zolbetuximab+mFOLFOX6 (modified 5-FU, folinic acid, oxaliplatin). Here is an analysis of CLDN18.2 expression and exploratory biomarkers from 2 studies of zolbetuximab alone or with mFOLFOX6 in G/GEJa. Methods: Data are from phase 1 (NCT03528629) and phase 2 (NCT03505320, ILUSTRO Cohorts 1 and 2) studies. Pts with CLDN18.2-positive locally advanced/metastatic G/GEJa received zolbetuximab alone (phase 1 [ineligible for SOC], n = 18; phase 2 Cohort 1 [≥3rd-line], n = 30) or with mFOLFOX6 (phase 2 Cohort 2 [1st-line], n = 21). Archival (any time before treatment), baseline (during screening or ≤3 months before first study treatment), and on-treatment (Cycle 3) tumor samples were collected when possible. CLDN18.2 expression and immune cell populations were assessed by IHC. Blood samples collected longitudinally while on treatment (phase 2 study) were analyzed for ADCC activity (ex vivo cell-based assay), circulating tumor antigens, and circulating tumor DNA (ctDNA). Results: Of 416 screened pts in both studies, 26.2% (n = 109), 9.6% (n = 40), and 36.1% (n = 150) had tumors that were CLDN18.2-positive in 1%–49%, 50%–74%, and ≥75% of tumor cells ( = strong to moderate staining intensity), respectively; 28.1% (n = 117) were CLDN18.2-negative (0/1+). Analysis of pre- and on-treatment tissue samples (n = 8 matched pairs) with zolbetuximab alone showed an increased trend in immune cell infiltration, with CD8+ T cells and CD163+ cells showing the most consistent trend. A trend of increased on-treatment vs baseline ADCC activity was observed in PBMCs collected from pts treated with zolbetuximab alone and with mFOLFOX6. Rapid and deep decreases in circulating tumor antigens (in pts with elevated antigen levels) and ctDNA were observed with best overall responses of both PR and SD. Conclusions: CLDN18.2 is a high-prevalence biomarker in G/GEJa. Treatment with zolbetuximab is associated with tumor and peripheral biomarker changes related to its proposed mechanism of action. Clinical responses observed in pts treated with zolbetuximab and mFOLFOX6 are associated with correlative biomarkers of activity including rapid deep molecular responses (ctDNA). Clinical trial information: NCT03528629 .

Effect of ethnicity and chemotherapy (mFOLFOX6) on zolbetuximab pharmacokinetics in patients with claudin 18.2-positive locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma (G/GEJ)

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Background: Zolbetuximab is a chimeric IgG1 monoclonal antibody that targets Claudin 18.2 (CLDN18.2), a tight junction protein that is normally confined to gastric mucosa but is retained in G/GEJ. A phase 2 (NCT01630083, FAST) trial demonstrated significantly prolonged survival with zolbetuximab + EOX (epirubicin, oxaliplatin, capecitabine) vs EOX in G/GEJ. Two global phase 3 studies are ongoing, comparing zolbetuximab + chemotherapy vs chemotherapy as first-line treatment in CLDN18.2-positive G/GEJ. This study assessed the influence of ethnic differences and chemotherapy on the pharmacokinetics (PK) of zolbetuximab in patients (pts) with G/GEJ and the potential effect of zolbetuximab on chemotherapy PK. Methods: In the Japanese phase 1 and global phase 2 studies, adult pts with CLDN18.2-postitive G/GEJ received zolbetuximab 800 mg/m2 IV on Cycle 1 Day 1 (Cycle 1 Day 3 in Cohort 2 of phase 2) then 600 mg/m2 Q3W. Phase 1 and Cohort 1A of the phase 2 study assessed zolbetuximab monotherapy in 21-day cycles. Cohort 2 of the phase 2 study assessed zolbetuximab + mFOLFOX (5-FU, folinic acid, oxaliplatin; 4 cycles) in 42-day cycles (Q2W from Cycle 1 Day 1). Blood samples for zolbetuximab PK following single and multiple doses, and for chemotherapy (5-FU and oxaliplatin) PK alone or with zolbetuximab were collected. Maximum serum drug concentration (Cmax) and area under the concentration-time curve from 0-21 days (AUC0-21) were assessed. Potential ethnic differences in zolbetuximab exposures across Japanese, other Asian (Korean and Taiwanese), and Western pts, and the potential drug-drug interaction between zolbetuximab and chemotherapy were evaluated. Results: Zolbetuximab concentration profiles and PK parameters were generally comparable across Japanese, other Asian, and Western populations (Table). Zolbetuximab PK properties were similar between monotherapy and combination therapy cohorts (Table). Chemotherapy PK was comparable with and without zolbetuximab. Conclusions: The analyses suggest no apparent ethnic differences in zolbetuximab PK across Japanese/Asian and Western pts and no PK interactions between zolbetuximab and mFOLFOX6. These results support the use of zolbetuximab and mFOLFOX without the need for dose adjustment in global phase 3 trials. Clinical trial information: NCT03505320, NCT03528629. [Table: see text]

Precision therapeutic targeting of human cancer cell motility

Increased cancer cell motility constitutes a root cause of end organ destruction and mortality, but its complex regulation represents a barrier to precision targeting. We use the unique characteristics of small molecules to probe and selectively modulate cell motility. By coupling efficient chemical synthesis routes to multiple upfront in parallel phenotypic screens, we identify that KBU2046 inhibits cell motility and cell invasion in vitro. Across three different murine models of human prostate and breast cancer, KBU2046 inhibits metastasis, decreases bone destruction, and prolongs survival at nanomolar blood concentrations after oral administration. Comprehensive molecular, cellular and systemic-level assays all support a high level of selectivity. KBU2046 binds chaperone heterocomplexes, selectively alters binding of client proteins that regulate motility, and lacks all the hallmarks of classical chaperone inhibitors, including toxicity. We identify a unique cell motility regulatory mechanism and synthesize a targeted therapeutic, providing a platform to pursue studies in humans.

In this study, the authors identify and validate a halogen-substituted isoflavanone able to inhibit prostate cancer cell motility, invasion and metastasis in vitro and in vivo. They demonstrate its ability to selectively inhibit activation of client proteins that stimulate cell motility.

An orthotopic murine model of human prostate cancer metastasis

Our laboratory has developed a novel orthotopic implantation model of human prostate cancer (PCa). As PCa death is not due to the primary tumor, but rather the formation of distinct metastasis, the ability to effectively model this progression pre-clinically is of high value. In this model, cells are directly implanted into the ventral lobe of the prostate in Balb/c athymic mice, and allowed to progress for 4-6 weeks. At experiment termination, several distinct endpoints can be measured, such as size and molecular characterization of the primary tumor, the presence and quantification of circulating tumor cells in the blood and bone marrow, and formation of metastasis to the lung. In addition to a variety of endpoints, this model provides a picture of a cells ability to invade and escape the primary organ, enter and survive in the circulatory system, and implant and grow in a secondary site. This model has been used effectively to measure metastatic response to both changes in protein expression as well as to response to small molecule therapeutics, in a short turnaround time.

Abstract 4752: Selective inhibition of cancer metastasis with a novel small therapeutic molecule

Prostate cancer (PCa) is the second most common cause of cancer death in US males. Death is typically caused by metastasis. Naturally occurring isoflavanones have been reported to be a class of compounds that effectively inhibit PCa motility and metastasis. This led us to use these compounds as a synthetic scaffold starting point. By integrating fragment-based diversification synthesis with chemi-driven biological selection, we discovered novel small molecule therapeutics with increased selectivity and potent efficacy. We thereby efficiently synthesized a new class of bioactive compounds that inhibit cell motility in vitro and inhibit human PCa metastasis in a murine model at low nanomolar concentrations. Extensive investigations indicate high specificity at the molecular and cellular levels, and failed to identify toxicity, even at high doses administered over extended periods. Importantly, efficacy against several cancer types was also demonstrated. Target validation studies used our lead as a chemical probe, and point to inhibition of ATM/ATR interaction with specific substrate proteins as important. Together, these studies indicate that we have successfully discovered a novel compound, acting upon a novel pharmacologic target, which selectively inhibits human PCa metastasis. Taken with our favorable preclinical toxicological data, these findings support movement of our lead compound into early phase human trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4752. doi:1538-7445.AM2012-4752

Abstract C177: Chemical-driven biological probing: Discovery of a novel antimetastatic drug

Chemicals constitute richly informative probes, have high resolving potential and are able to uncover complex biological processes. Harnessing this potential provides an avenue for the discovery of new therapeutics that act via novel mechanisms. We focused these principles upon an intractable problem: cancer metastasis. We started with a chemical scaffold with broad bioactivity, with desirable drug-like properties and that would support synthetic diversification. Initially focusing upon human prostate cancer (PCa) we then coupled fragment-diversification and novel synthetic routes to upfront positive selection screens (inhibition of cell motility) and negative selection screens (cell toxicity) in an iterative fashion. We thereby efficiently synthesized a new class of bioactive compounds that inhibits systemic PCa metastasis at low nanomolar concentrations. Efficacy against other cancer types was demonstrated. Extensive investigations indicate high specificity and no toxicity. Target validation studies point to inhibition of protein-protein interaction motifs. Together, these studies support the notion that this approach is powerful, can be broadly applied across biological systems, and constitutes a paradigm. Specifically, they have led to the discovery of a novel acting drug that inhibits human cancer metastasis.

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 C177.

Abstract B58: Discovery of a novel drug KBU2046 that inhibits conversion of human prostate cancer to a metastatic phenotype

Epidemiological evidence, preclinical studies and prospective phase II studies in humans indicate that the isoflavone, genistein, will inhibit the conversion of human prostate cells to an invasive, and ultimately, a metastatic phenotype. Though promising, genistein exerts many additional effects that have the potential for future toxicity in humans. We therefore sought to discover a new drug with improved efficacy and most importantly, with high specificity. Starting from an isoflavone chemical scaffold, we employed a fragment-based chemical synthesis diversification approach, and coupled it to three in vitro screens: 1) cell invasion (efficacy), 2) cell growth inhibition (an indicator of general toxicity), and 3) several measures of estrogenic activity. From multiple synthesis/biological assay iterations we developed a refined structure-activity relationship map, thereby leading us to discover KBU2046. KBU2046 represents a new and chemically distinct class of bioactive compounds. It has greater anti-invasion efficacy than genistein, and more importantly, no cell toxicity or estrogenic activity. Extensive toxicity studies in mice were negative. At low nanomolar blood concentrations, KBU2046 will prevent orthotopically implanted human prostate cancer cells from forming metastasis in a dose-responsive fashion. In summary, we have successfully discovered and developed a compound that prevents progression to a metastatic phenotype for human prostate cancer. We are in the process of bringing KBU2046 into the clinic, with the goal of preventing death from the second most common cause of cancer related death in men.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):B58.