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Pharmacokinetic parameters of guadecitabine and decitabine after guadecitabine injection

LINE1 changes in tumor CpG 1-3 on cycle 1 day 8 from baseline. LINE1 changes in tumor DNA in individual patient biopsy samples.

LINE1 changes in circulating DNA CpG 1-3 as compared to baseline.

Purpose:Chemotherapeutic resistance eventually develops in all patients with metastatic colorectal cancer (mCRC). Gene silencing through promoter demethylation is one potential reversible mechanism of resistance with administration of hypomethylating agents. We evaluated the safety and tolerability of guadecitabine and irinotecan in patients with mCRC previously treated with irinotecan.Patients and Methods:In this 3+3 dose-escalation study, patients with mCRC previously exposed to irinotecan received guadecitabine days 1 to 5 of a 28-day cycle and irinotecan 125 mg/m2 days 8 and 15 [dose level (DL) 1, guadecitabine 45 mg/m2; DL −1: guadecitabine 30 mg/m2; DL −1G: guadecitabine 30 mg/m2 with growth factor support (GFS); DL 1G: guadecitabine 45 mg/m2 with GFS].Results:Twenty-two patients were treated across four DLs. Dose-limiting toxicities were neutropenic fever (DL 1 and −1G), biliary drain infection (DL −1), colonic obstruction (DL −1), and severe dehydration (DL 1G). Most common toxicities were neutropenia (82% any grade, 77% Grade 3/4), neutropenic fever (23%), leukopenia (73% any grade, 50% Grade 3/4), and injection site reactions (64% total, 0% Grade 3/4). Patients received a median of 4.5 cycles of treatment; 12/17 evaluable patients had stable disease as best response, with one having initial disease progression but subsequently durable partial response. Circulating tumor DNA showed decrease in global demethylation by LINE-1 after treatment.Conclusions:We report the first study of chemo-priming with epigenetic therapy in gastrointestinal cancers. Guadecitabine 45 mg/m2 and irinotecan 125 mg/m2 with GFS was safe and tolerable in patients with mCRC, with early indication of benefit. These data have provided the basis for an ongoing phase II randomized, multicenter trial.

Background: SHP2 is an oncogenic tyrosine phosphatase that transduces receptor tyrosine kinase signaling to the RAS/MAPK pathway via its phosphatase-mediated regulation of guanine nucleotide exchange factors. ERAS-601 is a potent, selective, and orally bioavailable allosteric inhibitor of SHP2. In combination with cetuximab, an antibody that targets epidermal growth factor receptor (EGFR), ERAS-601 has demonstrated robust nonclinical activity in human papillomavirus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) and RAS/RAF wild-type colorectal cancer (CRC) tumors. Method: FLAGSHP-1 is the first-in-human trial of ERAS-601 administered as monotherapy and in combination with other cancer therapies in patients with advanced or metastatic solid tumors. The primary objectives are to characterize the safety profile, determine the maximum tolerated dose (MTD)/recommended dose (RD), and characterize the pharmacokinetics (PK) profile of ERAS-601 as a monotherapy and in combination with other cancer therapies. Secondary objectives include tolerability and antitumor activity in solid tumors. Presented here are results from the combination dose escalation cohorts in which patients received ERAS-601 twice a day for three weeks followed by a one-week break (BID 3/1) in combination with cetuximab (500mg/m2) administered every 2 weeks (Q2W) on a 28-day cycle. Results: As of October 31, 2022, a total of 15 patients with previously treated advanced or metastatic solid tumors received ERAS-601 BID 3/1 at the following dose levels: 20 mg BID 3/1 (n=4), 40 mg BID 3/1 (n=8), or 60 mg BID 3/1 (n=3) in combination with cetuximab. Combination therapy MTD was determined​ to be 40 mg BID 3/1. ERAS-601 Treatment Related Adverse Events (TRAEs) at or below the MTD were all Grade 1 and 2. TRAEs occurring in ≥20% of patients included diarrhea (27%), AST increase (27%), ALT increase (20%), dermatitis acneiform (20%). Grade ≥3 TRAEs included Grade 4 hypokalaemia, Grade 3 diarrhea, platelet count decreased anemia (each 7%); high grade TRAEs were only observed at 60 mg BID 3/1 (above the MTD). Dose limiting toxicities (DLTs) were only observed at the 60mg BID 3/1 dose levels and included Grade 3 platelet count decreased (n=1) and Grade 4 hypokalemia (n=1). Pharmacokinetics of ERAS-601 and cetuximab in combination were generally comparable to historical monotherapy PK values, suggesting lack of drug-drug interaction. The evaluation of clinical activity is still ongoing. Conclusions: ERAS-601 in combination with cetuximab in patients with previously treated advanced or metastatic solid tumors shows promising preliminary safety and tolerability with reversible and manageable TRAEs. Further evaluation in relevant tumor types are ongoing. Citation Format: Meredith McKean, Ezra Rosen, Minal Barve, Tarek Meniawy, Judy Wang, David S. Hong, Jennifer Yang, Zhengrong Li, Roxana Picard, Les Brail, Daniela Vecchio, Thomas John, Ezra Cohen, Gregory Obara, Aparna Parikh. Preliminary dose escalation results of ERAS-601 in combination with cetuximab in FLAGSHP-1: a phase I study of ERAS-601, a potent and selective SHP2 inhibitor, in patients with previously treated advanced or metastatic solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT184.

RMC-4630 is a potent, selective, orally bioavailable allosteric inhibitor of SHP2, a central node in the RAS signaling pathway. Preclinical data have demonstrated that RMC-4630 can shrink tumors carrying certain mutations in the RAS pathway such as KRASG12C, NF1LOF, and BRAFClass3. Longitudinal circulating tumor DNA (ctDNA) was isolated from blood using GuardantOMNI in 80 patients with relapsed/refractory solid tumors in the phase 1 dose-escalation trial of RMC-4630 (NCT03634982) to characterize and confirm RAS pathway mutations and to evaluate molecular responses in patients receiving RMC-4630 monotherapy. Safety, PK and efficacy findings from this study are reported in a separate abstract. 78 of 80 patients had baseline somatic mutations detected in plasma, of which 60 were either KRASG12X, NF1LOF, or BRAFClass3; 48 of these 60 patients also had on-treatment ctDNA assessments and these patients constitute the population reported here. 9 of 48 patients (19%) had KRASG12C detected at baseline, available scan results and a ctDNA sample after 4 weeks of receiving RMC-4630. A decrease in KRASG12C variant allele frequency (VAF) was detected in 5/9 patients (56%) with clearance in 1 patient with a partial response. Decrease in KRASG12C VAF was associated with change in tumor volume (PCC=0.85, p=0.008), preceding scan results by approximately 1 month, suggesting that change in KRASG12C VAF may be an early measure of drug activity or possibly response. 5 of 48 patients (10%) had NF1LOF detected at baseline. A decrease, or stability in NF1LOF VAF on treatment compared to baseline was detected in 4 (80% of all NF1LOF patients). The decrease in NF1LOF VAF was not associated with change in tumor volume and may represent effects of RMC-4630 on a subclone harboring NF1LOF. One patient had a detectable BRAFClass3 mutation at baseline, which decreased in VAF on treatment compared to baseline. Of the remaining patients there were 12 KRASG12D, 9 KRASG12V and other KRASG12X. The majority progressed with an increase in VAF of all mutations including KRASG12X, suggesting that the KRASG12X-containing clone is responsible for escape from single agent RMC-4630. In most instances the increase in KRASG12X VAF in blood preceded determination of clinical progression. Longitudinal assessment of ctDNA indicates that some patients with RAS-addicted tumors undergo a molecular response on treatment with the SHP2 inhibitor RMC-4630. Citation Format: Josie L. Hayes, Marianna Koczywas, Sai-Hong Ignatius Ou, Pasi A. Janne, Jose M. Pacheco, Susanna Ulahannan, Judy S. Wang, Howard A. Burris, Jonathan W. Riess, Caroline McCoach, Michael S. Gordon, Anna Capasso, Ariel Chen, Richa Dua, Bojena Bitman, Martha Guerra, Hongfang Wang, Xiaolin Wang, Eric Haura. Confirmation of target inhibition and anti-tumor activity of the SHP2 inhibitor RMC-4630 via longitudinal analysis of ctDNA in a phase 1 clinical study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB054.

RMC-4630 is a potent, selective, orally bioavailable allosteric inhibitor of SHP2, a central node in the RAS signaling pathway. In preclinical models, SHP2 inhibition not only directly inhibited tumor growth through suppression of tumor-intrinsic RAS signaling, but also resulted in transformation of the tumor immune microenvironment, characterized by an increase in CD8+T cell infiltrates and selective depletion of pro-tumorigenic M2 macrophages. In this study, we evaluated pharmacodynamic biomarkers in blood and tumors from patients in the RMC-4630 phase I monotherapy clinical trial (NCT 03634982) by using flow cytometry and immunohistochemistry (IHC). Safety, PK and efficacy data are reported in a separate abstract. Longitudinal analysis of immune cell phenotyping in blood was conducted in 35 patients. There was a trend for lower pre-study monocytic myeloid-derived suppressor cell (mMDSC) to be associated with a better clinical outcome on RMC-4630 therapy. While the proportion of circulating T cell and B cell populations did not change, both blood mMDSC and total monocytes were significantly reduced during RMC-4630 administration. Furthermore, tumor volumes changes, and the proportion of patients with SD versus PD, positively correlated with the ratio of mMDSCs to total monocytes on RMC-4630 treatment. Inhibition of pERK was observed in a subset of patients. Three paired tumor biopsies from efficacy-evaluable patients, including 1 PR, 1 SD and 1 PD, were available for tumor microenvironment analysis by multiplexed-IHC assays. Increase in tumor infiltrating T cells in the tumors of one patient with a PR and another with SD was observed on RMC-4630 therapy. Inhibition of tumor PD-L1 expression and a decrease in M2 macrophages was also observed on treatment in the tumor biopsy of the PR patient. Collectively, the preliminary clinical biomarker data supports the preclinical observations that SHP2 inhibition with RMC-4630 modulates both innate and adaptive anti-tumor immunity. Citation Format: Ariel Yung-Chia Chen, Eric Haura, Jose Pacheco, Marianna Koczywas, Michael Gordon, Susanna Ulahannan, Howard A. Burris, Sai-Hong Ignatius Ou, Judy S. Wang, Jonathan W. Riess, Caroline McCoach, Anna Capasso, Elsa Quintana, Josie Hayes, Richa Dua, Bojena Bitman, Martha Guerra, Hongfang Wang, Xiaolin Wang, Pasi A. Janne. Modulation of innate and adaptive immunity in blood and tumor of patients receiving the SHP2 inhibitor RMC-4630 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB050.

Background: Gut microbiome composition affects response to PD-1 blockade; and recent proof of concept studies suggest that gut microbiome manipulation is effective in reversing resistance to PD-1 blockade. VE800 is an oral live biotherapeutic consisting of 11 distinct non-pathogenic, non-toxigenic, commensal bacterial strains manufactured in lyophilized form. VE800 induces CD8+ T cell infiltrate into tumors; and significantly enhances anti-tumor activity of PD-1 blockade preclinically in multiple tumor models in a CD103+ dendritic cell and major histocompatibility (MHC) class I dependent fashion (Tanoue et al., 2019). Retrospective analysis of cancer patient's (pt) samples also suggests that greater VE800 strain abundance is associated with improved response to PD-1 blockade. The objective of this phase I study is to evaluate the safety, tolerability, and clinical activity of VE800 administered orally in combination with nivolumab in pts with select cancers. Methods: CONSORTIUM-IO (NCT04208958) is an open-label, first-in-human study evaluating VE800 and nivolumab combination in pts with anti-PD-1/PD-L1 relapsed/refractory melanoma, anti-PD-1/PD-L1 naïve gastric/gastroesophageal junction (GEJ) adenocarcinoma and anti-PD-1/PD-L1 naïve microsatellite-stable (MSS) colorectal cancer. Following a 5-day course of oral vancomycin 125mg QID, VE800 will be administered daily along with nivolumab (480mg Q4W). A single dose level of VE800 will be evaluated. In the interests of maximizing safety, a Simon 2-stage design will be used for each disease cohort. Although no dose-limiting toxicities (DLT) are expected, the first 3 pts will be enrolled serially 1 week apart; and safety data of the first 6 pts will be reviewed prior to further accrual. Pts will continue to receive VE800/nivolumab combination until disease progression or unacceptable toxicity. Primary endpoints include safety, tolerability; and clinical activity by objective response rate (ORR) per RECIST v1.1. Secondary endpoints include duration of response (DOR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS); and metagenomic strain-level analysis of degree/duration of VE800 strain colonization. Exploratory endpoints include tumor and blood immunophenotyping, serum/stool metabolomics and global changes in fecal microbiome composition. CONSORTIUM-IO is currently actively enrolling pts. Citation Format: Diwakar Davar, Judy S. Wang, Michael Cecchini, Zev Wainberg, Martin Gutierrez, Anita Turk, Rose Szabady, Jason Norman, Bernat Olle, Bruce Roberts, Dmitri Bobilev. Consortium-IO: A safety and efficacy study of VE800 in combination with nivolumab in previously treated patients with select advanced metastatic cancers [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 CT246.

Background: Preclinical data suggest that adavosertib (AZD1775), a highly selective Wee1 inhibitor, enhances the antitumor effect of PARP inhibitors such as olaparib. The dose-escalation part of this Phase Ib study (NCT02511795) investigated the safety and tolerability of adavosertib plus olaparib in patients (pts) with refractory solid tumors to determine a maximum tolerated dose (MTD) and recommended Phase II dose (RP2D). Methods: Pts received adavosertib (QD or BID) for 3 consecutive days with 4 days off treatment (3/4), or 5 consecutive days with 2 days off (5/2), plus olaparib (BID) for 14 or 21 days of a 21-day cycle (Table). The MTD was the highest dose at which 7 days, gr 3 thrombocytopenia with gr ≥2 bleeding, non-hematologic gr ≥3 AEs (excluding nausea, vomiting or diarrhea that responds to supportive care), liver function gr ≥3 AEs lasting >48 hours or changes consistent with Hy’s Law, or any other toxicity that disrupted dosing for >7 days. Results: 119 pts were treated (84 female; median age 59; most common primary tumor sites: ovary [21%], breast [16%], lung [12.6%]) (Table). The most common gr ≥3 AEs were anemia (n=28, 23.5%), neutropenia (n=26, 21.8%), and thrombocytopenia (n=20, 16.8%) (all grouped terms). The most common DLTs were thrombocytopenia (n=4) and neutropenia (n=4); two pts experienced both. There were 4 SAEs with an outcome of death, 1 was treatment related. ORR for the total population, cohort 4.2 and cohort 7.4 was 11.1%, 30.8% and 0%, respectively. DCR was 55.7%, 76.9% and 53.8%, respectively. PK and biomarker data will be presented. Conclusions: Treatment with adavosertib plus olaparib showed antitumor activity, mostly at the MTD/RP2D for the BID schedule, which was determined to be adavosertib 175 mg (3/4) for 2/3 weeks plus olaparib 200 mg BID. The RP2D for QD schedule was adavosertib 200 mg (3/4) for 2/3 weeks plus olaparib 200 mg BID. Summary of study cohortsCohortAdavosertib doseOlaparib doseAdavosertib schedule, daysOlaparib schedule, daysPatients, n (evaluable,* n)Patients with a DLT, n (%)Grade ≥3 AEs,† n (%)ORR, n (%)DCR, n (%)1125 mg BID (3/4)100 mg BID1–3/8–101–143 (2)01 (33.3)03 (100)2150 mg BID (3/4)100 mg BID1–3/8–101–144 (4)02 (50)1 (25)2 (50)3.1175 mg BID (3/4)100 mg BID1–3/8–101–144 (2)03 (75)03 (75)3.2150 mg BID (3/4)200 mg BID1–3/8–101–147 (5)04 (57.1)1 (14.3)5 (71.4)4.1175 mg BID (3/4)200 mg BID1–3/8–101–147 (7)04 (57.1)1 (14.3)4 (57.1)4.2175 mg BID (3/4)200 mg BID1–3/8–101–2114 (11)1 (9.1)9 (64.3)4 (30.8)10 (76.9)4.3175 mg BID (3/4)200 mg BID1–3/8–10/15–171–2114 (11)2 (18.2)13 (92.9)1 (7.7)7 (50)5175 mg BID (3/4)300 mg BID1–3/8–101–145 (5)1 (20.0)3 (60.0)2 (50)4 (100)6.1250 mg QD (5/2)200 mg BID1–5/8–121–217 (4)2 (50.0)6 (85.7)1 (20)1 (16.7)6.2200 mg QD (5/2)200 mg BID1–5/8–121–217 (5)2 (40.0)4 (57.1)01 (14.3)7.1250 mg QD (3/4)200 mg BID1–3/8–101–2116 (14)2 (14.3)12 (75)010 (62.5)7.2250 mg QD (3/4)200 mg BID1–3/8–10/15–171–214 (4)1 (25.0)3 (75)1 (25)3 (75)7.3300 mg QD (3/4)200 mg BID1–3/8–101–213 (3)1 (33.3)2 (66.7)007.4200 mg QD (3/4)200 mg BID1–3/8–101–2113 (12)1 (8.3)3 (23.1)07 (53.8)8.1200 mg QD (3/4)300 mg BID1–3/8–101–2111 (9)1 (11.1)4 (36.4)04 (40)*Evaluable patients received >75% of the planned dose of adavosertib and olaparib; †Common Terminology Criteria for Adverse Events. DCR, disease control rate; ORR, objective response rate Citation Format: Erika Hamilton, Gerald S. Falchook, Judy S. Wang, Siqing Fu, Amit Oza, So Karen, Esteban Rodrigo Imedio, Sanjeev Kumar, Lone Ottesen, Ganesh M. Mugundu, Juliann Chmielecki, Suzanne Jones, David R. Spigel, Bob T. Li. Phase Ib study of adavosertib in combination with olaparib in patients with refractory solid tumors: Dose escalation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT025.

IntroductionMVT-5873, a fully human IgG1 monoclonal antibody (mAb), targets sialyl Lewis A (sLea), an epitope on CA19-9. CA19-9 is expressed in pancreatic (PDAC) and other GI cancers, plays a role in tumor adhesion and metastasis, and is a marker of an aggressive tumor phenotype. MVT-5873 is active as a single agent and in combination with nab-paclitaxel (nab-P) and gemcitabine (gem) in murine xenografts. MethodsSingle agent: for each 28-day treatment cycle, MVT-5873 was given IV every second week (Group 1) or weekly (Group 2) at doses ranging from 1 to 3 mg/kg. Combination with nab-P and gem: for each 28-day treatment cycle MVT-5873 was administered IV weekly (1.0mg/kg or 0.125mg/kg) followed by IV infusion of 125 mg/m2 of nab-P and then 1000mg/m2 gem, on day 1, 8 and 15 (Group 3). Eligible patients had recurrent progressive (single agent) or newly diagnosed (combination), locally-advanced or metastatic PDAC or other CA19-9+ malignancy and ECOG PS ≤1. Dose escalation followed a standard 3+3 design with a 10 patient expansion at the maximally tolerated dose (MTD). Trial endpoints include safety, MTD, dose limiting toxicities (DLT), pharmacokinetics (PK) and efficacy. Exploratory endpoints include changes in serum CA19-9 levels.ResultsAs of 7-September-2017, data are available for single agent N=32 in Groups 1 (N=9) and 2 (N=23) at 1, 2, 2.5 and 3 mg/kg and combination Group 3 (N=6) at 1.0 and 0.125mg/kg. DLTs of transient grade 3 elevations in AST, ALT, and total bilirubin were encountered in the single agent groups at 2, 2.5 and 3mg/kg in both single agent groups and in the combination group at 1mg/kg. Single agent liver function laboratory abnormalities typically emerged and resolved within a week of dosing although they were more persistent in the combination treated patients. Other toxicities associated with all groups included low grade GI toxicity (abdominal pain/cramps/diarrhea/nausea) and infusion reactions. Infusion reactions were mitigated with pre-medications and an increase in the infusion time. Combination DLTs for MVT-5873 at 1mg/kg included AST, ALT, and bilirubin elevations as well as neutropenia and pneumonitis resulted in significant dose de-escalation. MVT-5873 dosed at 0.125 mg/kg in combination was generally well tolerated. Single agent activity included SD of >4 months in 5 of 32 of patients with an MTD established at 1 mg/kg. Combination activity at 0.125 mg/kg MVT-5873 with nab-P/gem included 2 PRs and 1 SD in 3 patients. Interestingly, sustained suppression below ULN of CA19-9 levels was observed in 3 of the 6 patients in the combination arm and >95% CA19-9 reduction at the 0.125mg/kg combination dose. Dose escalation in this arm is in progress, and updated safety, PK/PD, and efficacy data will be presented.ConclusionsSingle agent MVT-5873 appears safe and tolerable at biologically active doses. DLTs included reversible liver function abnormalities. Determination of the MTD in combination with first line nab-P/gem is underway and preliminary response data are encouraging. Overall, the safety profile, efficacy, and reductions in serum CA19-9 levels over time support further development of MVT-5873 in this indication both as a single agent and in combination. Citation Format: Eileen Mary O'Reilly, Judy Sing-Zan Wang, Kenneth H. Yu, Maeve Aine Lowery, Anna M. Varghese, Johanna C. Bendell, Erkut Hasan Borazanci, Hayley Estrella, Kimberly Fowler, Mariella Hoskins, Stephanie Bussen, Teresa J. Melink, Christine M. Kearns, H Toni Jun, Paul W. Maffuid, John C. Gutheil, Todd Michael Bauer. Preliminary phase I data comparing HuMab-5B1 (MVT-5873), a monoclonal antibody targeting sLea, as a single agent and in combination with first line nab-paclitaxel and gemcitabine in patients with CA19-9 positive pancreatic cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-B25.

BACKGROUND: DMUC4064A is a TDC comprising a humanized anti-MUC16 IgG1 and a potent anti-mitotic agent, monomethyl auristatin E (MMAE) through a protease-labile linker through engineered cysteine at a Drug Antibody Ratio (DAR) of 2. The use of engineered cysteines is intended to allow more homogenous conjugation, which in turn can improve the overall performance of the TDC (i.e. slower clearance), compared to the conventional ADC (prepared by stochastic conjugation to interchain disulfide bond cysteines). MUC16 is a transmembrane glycoprotein overexpressed on ovarian cancer cells, which in its soluble form is known as Carbohydrate antigen 125 (CA125). A phase I study in PROC patients is ongoing to assess the safety, efficacy and PK of DMUC4064A given every 3 weeks (Q3W). METHODS: Serum/plasma samples at multiple time points were quantified for three analytes (unconjugated MMAE, DMUC4064A total antibody (tAb), and DMUC4064A conjugate (measured as antibody-conjugated MMAE, acMMAE)). The cycle 1 PK was assessed by standard non-compartmental analysis. The impact of serum CA125 on PK was investigated. RESULTS: Within the tested dose range (1.0-5.6 mg/kg), acMMAE and tAb showed nonlinear PK with more than dose-proportional exposure at the higher doses (4.8 mg/kg and 5.6 mg/kg). A clear correlation of acMMAE with tAb exposure was observed. The PK of DMUC4064A at the highest dose tested (5.6 mg/kg), as measured by acMMAE, showed a volume of distribution of approximately 52 mL/kg and a clearance of ~7 mL/day/kg with a terminal half-life of approximately 5.5 days. Unconjugated MMAE exposure was consistently lower than acMMAE with a mean Cmax approximately 150-300 fold lower than that of acMMAE. At higher doses (>4.0 mg/kg), unconjugated MMAE exposure was variable and overlapping across doses. Accumulation of all analytes was minimal after repeated dosing (Q3W). Based on preliminary data from this ongoing study, baseline CA125 levels have not shown any apparent impact on cycle 1 exposure. Compared to the conventional anti-MUC16 ADC (DMUC5754A, DAR 3.5) at 2.4 mg/kg (MTD), the TDC DMUC4604A at 5.6 mg/kg demonstrates a greater than 3 fold slower acMMAE clearance1. CONCLUSION: In this ongoing study of DMUC4604A, nonlinear PK of acMMAE and tAb were observed over the dose range studied, and exposures of acMMAE and tAb were highly correlated. This is the first report of clinical PK data of a TDC demonstrating slower clearance compared to a conventional ADC format. 1 Liu JF, et al. Annals of Oncology 27: 2124–2130, 2016 Citation Format: Amit Garg, Gaohong She, Ian Donatello, Matts Kagedal, Douglas D. Leipold, Ola Saad, Joyce Liu, Kathleen Moore, Erika Hamilton, Howard Burris, Judy Wang, Michael Birrer, Eric Humke, Sandhya Girish. Pharmacokinetics of a THIOMABTM antibody drug conjugate (TDC): DMUC4064A in a phase 1 study with platinum-resistant ovarian cancer [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 CT092. doi:10.1158/1538-7445.AM2017-CT092