Abstract Prostate cancer (PCa), the second most common cancer, is still a major cause of morbidity and mortality among men worldwide. A particularly aggressive group of PCa, where prognostic biomarkers are still needed, are clinically defined high-risk PCa. We had previously shown that the survival and proliferation factor progranulin (GP88) is a prognostic marker for primary PCa. We aimed in this study to characterize GP88 protein expression in high-risk PCa by immunohistochemistry and to examine its association with prognosis. Immunohistochemical staining for GP88 was performed with TMA of samples from 94 high-risk PCa patients using an H-score. GP88 staining was in a range of 3.69 to 252.51 (median: 109.28). The association of GP88 staining with prognosis was examined by survival analyses (Kaplan–Meier, multivariate Cox’s regression analysis). Elevated GP88 expression was associated with a shorter clinical progression-free survival (CPFS) in all PCa patients (P = 0.043), and in the following patient subgroups: Elder PCa patients (> 67 years; P = 0.020), patients with pT3 tumors (P = 0.008), with Gleason scores GS5 and GS6 (P = 0.033 and P = 0.030), and patients without radiation therapy (P = 0.009) at considering that only four patients received an adjuvant radiation therapy. In a multivariate Cox’s regression analysis, increased GP88 protein expression (RR = 2.98; P = 0.049) and the preoperative PSA level (RR = 5.29; P = 0.030) appeared as independent prognostic factors for clinical progression. Interestingly, lower GP88 staining in corresponding low Gleason lesions was correlated with the presence of immune cells, suggesting an immune cell suppressive effect of GP88. Altogether, Progranulin (GP88) protein positivity appears very likely to be an independent prognostic factor for clinical progression in high-risk PCa patients.

TPS2669 Background: Progranulin also called GP88/PGRN plays a major role as an autocrine growth & survival factor associated with resistance to standard of care (SOC) targeted and chemo therapies in several cancers including breast cancer (BC) & non-small cell lung carcinoma (NSCLC): 1) GP88 is expressed in 80% breast invasive ductal carcinomas & is negative in normal mammary tissue; 2) GP88 tumor expression is a prognostic indicator of recurrence & survival in BC, NSCLC & prostate cancer patients (pts) 4) Elevated serum GP88 levels are present in several cancers including metastatic breast cancer (MBC), lung & prostate cancer pts compared to healthy subjects; 5) Elevated/rising GP88 serum levels in MBC pts are associated with disease progression & inferior survival. These results make GP88 an ideal therapeutic & diagnostic target in solid tumors. An anti-human PGRN/GP88 monoclonal antibody inhibiting PGRN/GP88 action was developed & expressed in CHO cells. Pharmacology, GMP manufacturing, formulation, stability studies & GLP toxicology studies in non-human primates were done. The IND application cleared by the US FDA led to the FIH AG01 study in adults with advanced solid tumors lacking effective therapies. Methods: A Phase 1 FIH dose-escalation study was designed in pts with advanced solid tumor malignancies, the study is approved by the University of Maryland IRB. AG01 monoclonal antibody is administered intravenously (IV) over 90 minutes every 14 days +/- 1 day; DLT observation period is the 1st cycle=28days, with AGO1 Dose levels of,1mg/kg, 2mg/kg, 4mg/kg, 6mg/kg, 8 mg/kg. Initially accelerated titration design (1pt/dose level) was followed by 3+3 design). Eligibility criteria include pathologically confirmed diagnosis of advanced/relapsed/refractory solid tumor malignancy; failed >=1 SOC therapy or not a candidate/declines SOC therapy, ECOG <=2, adequate organ/bone marrow function, at least 1 RECIST 1.1 measurable and/or evaluable lesion. Tumor imaging-every 2 cycles (8 weeks) is used for response assessment. Primary objective is to determine the maximum tolerated dose MTD and/or maximum administered dose MAD of AG01 in the target population. Secondary objectives are to determine the RP2D, safety, tolerability, PKs, immunogenicity (ADA) & the preliminary anti-tumor activity of AG01 in pts with advanced solid tumors. Exploratory objectives will determine PGRN/GP88 expression in tumor tissue & PGRN/ GP88 blood levels (A&G’s IHC & ELISA test). The study is ongoing; & pts are currently enrolled. A parallel prospective study investigates the association of serum GP88 in MBC pts with response to SOC therapy and progression of disease based on RECIST 1.1 criteria. These studies are supported by NCI grants R44CA224718 and CA210817. Clinical trial information: NCT05627960 .

TPS3180 Background: GP88/PGRN is the largest member of the granulin/epithelin family. We demonstrated GP88’s role as an autocrine growth & survival factor in breast cancer (BC): in ER+BC cells, GP88 stimulates proliferation & confers resistance to anti-estrogen therapy & aromatase inhibitors;GP88 is expressed in 80% of invasive ductal carcinomas & is negative in normal mammary tissue; GP88 tumor expression is a prognostic indicator of recurrence & death in BC pts; Elevated GP88 serum level in metastatic BC patients (pts) is associated with disease progression. PGRN/GP88 is overexpressed in several other solid tumors (non-small cell lung carcinoma, colorectal, bladder, ovarian, prostate & brain). In advanced NSCLC & prostate pts, elevated serum PGRN/GP88 have been found. These results make GP88/PGRN an ideal therapeutic & diagnostic target in BC and other solid tumors. An anti-human PGRN/GP88 monoclonal antibody (AG01) inhibiting PGRN/GP88 action was developed & expressed as recombinant antibody in CHO cells. Pharmacology, GMP manufacturing, formulation, stability studies & GLP toxicology studies in non-human primates were done. The IND application was cleared by the FDA to proceed with the first-in-human (FIH) AG01 study in adult subjects with advanced solid tumors. Methods: This IRB approved FIH study, will be conducted in 2 stages, dose escalation (1A) and dose expansion (1B). The 1A part is ongoing, with the 1 + (3+3) design. In the 1A part the AG01 is administered intravenously (IV) over 90 min. every 14 days +/- 1 day, 1 cycle = 28days, DLT assessments occur in the first 28 days of treatment. Five dose levels of AG01 & a -1 level are planned (level -1-0.5mg/kg, & 1mg/kg, 2mg/kg, 4mg/kg, 6mg/kg, 8 mg/kg). In 1A part of the study, initially an accelerated titration design (1pt/dose level) was utilized to guide dose progression & estimation of the maximum tolerated and/or administered dose (MTD/MAD). Eligibility criteria for 1A part include pts with advanced relapsed/refractory solid tumor malignancies who failed 1 or more standard of care (SOC) therapies or for whom no SOC treatment exists or is not tolerated, at least 1 RECIST1.1 measurable lesion, ECOG < = 2, Life expectancy > = 12wks, adequate organ & bone marrow function, willing to sign informed consent & follow study procedures. Primary objective (1A) is to determine the MTD and/or MAD of AG01. Secondary objectives: to determine the recommended phase 2 dose (RP2D), safety, tolerability, the PKs, immunogenicity & the preliminary anti-tumor activity of AG01. Exploratory objectives:todetermine PGRN/GP88 expression in tumor tissue & PGRN/ GP88 blood levels (A&G’s IHC & ELISA test). This study is registered at NCT05627960. The study is supported by NCI grants NCI R44 CA224718 & CA162629. Clinical trial information: NCT05627960 .

Antibody Drug Conjugates (ADCs) are attractive for developing cancer-targeted therapies, particularly for cancers with unmet needs. Identification of a druggable internalising cell-surface target enables the development of internalising monoclonal antibodies to deliver toxic payloads directly to the cancer cells. Using immunohistochemistry, we screened various non-cancerous and cancerous tissue sections to assess PTGFRN expression levels. We produced hybridoma lines that produce fully human antibodies against the PTGFRN extracellular domain. After screening, we conjugated the cytotoxic payload Duocarmycin to an antibody candidate and tested its efficacy in in vitro assays, as well as in vivo xenografted athymic nude mice. We showed that PTGFRN expression was undetectable in non-cancerous tissue samples and overexpressed in several patient-derived cancer tissue samples. We produced a hybridoma line that produces a fully human IgG1 (8C7) against PTGFRN. 8C7 binds to cell-surface PTGFRN, inducing endocytosis of PTGFRN. Direct conjugation of Duocarmycin to 8C7 resulted in an antibody-drug conjugate that showed high potency in in vitro and in vivo models for three PTGFRN-expressing cell lines examined, A431, DAOY, and MSTO, while it had no effect on PTGFRN-negative MDA-MB-231. 8C7-ADC administered via intraperitoneal injection to xenografted mice showed inhibition of tumour formation and growth with no effect on body weight and organ weights. These findings further validate PTGFRN as a target for antibody-drug conjugate development for cancers with unmet needs.

Abstract Progranulin (PGRN/GP88) is an 88 kDa glycoprotein characterized by seven and a half double cysteine rich repeats which is the largest member of the granulin-epithelin protein family. PGRN/GP88 has been demonstrated as a biological driver of tumorigenesis, survival, and drug resistance in several cancers including breast cancer (BC), lung prostate, ovarian and digestive cancers. PGRN/GP88 tissue expression is an independent prognostic factor of recurrence in breast, lung cancers while elevated serum PGRN/GP88 level in metastatic breast, lung, ovarian and prostate cancer patients. Elevated PGRN/GP88 levels are associated with poor outcomes such as progression and shortened survival. An anti-human PGRN/GP88 monoclonal antibody able to inhibit the the in vitro and in vivo action of human PGRN/GP88 has been developed, chimerized and expressed in CHO cells. All IND enabling activities including pharmacology, GMP manufacturing, formulation and GLP toxicology studies have been conducted. The IND application has been filed and cleared by the Food and Drug Administration. A first-in-human, first-in-class phase 1 safety and efficacy clinical study of AG01 in patients with solid tumors and advanced disease with special focus on patients with breast, lung and ovarian cancers has been initiated and is on-going at the University of Maryland Greenebaum Cancer Center. The trial is registered as NCT05627960 to clinicaltrials.gov site. The presentation will provide an update on the number of patients enrolled in this on-going phase 1A trial. Supported by grants R44CA162629 and R44CA224718 from the National Cancer Institute to GS. Citation Format: Katherine Tkaczuk, Paula Rosenblatt, Ranee Mehra, Katherine Scilla, Nancy Tait, Binbin Yue, Ginette Serrero. On-going phase 1A clinical trial of A01, a chimerized monoclonal antibody to Progranulin/Glycoprotein 88 (GP88) in patients with advanced malignancy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-18-06.

Abstract Advanced carcinomas of the lung or the breast are characterized by invasiveness and poor survival. Identifying novel targeted therapies to potentiate standard of care (SOC) therapy, remains an unmet need. In the past 4 years, numerous targeted therapies in Oncology have been approved by the Food and Drug Administration (FDA). However, the identification of targeted therapies against direct tumor biological drivers remains important. Progranulin (PGRN/GP88) is a biological driver of tumorigenesis, survival, and drug resistance in multiple cancers including breast and lung cancers. PGRN/GP88 tissue expression is an independent prognostic factor of recurrence and mortality while elevated serum PGRN/GP88 level is associated with poor outcomes such as progression of disease and shortened survival. The importance of inhibiting PGRN/GP88 expression or action effect on the proliferation and tumor growth of several cancers has been established by several laboratories including ours. In the current study, in association with Precision Antibody, we developed anti-PGRN/GP88 fully human monoclonal antibodies by immunizing TC transgenic humanized mice with recombinant human progranulin. Within 60 days following the start of immunization, several fully human anti-progranulin monoclonal antibodies were developed, characterized by several functional assays including neutralization, inhibition of PGRN/GP88 cell surface binding, proliferation, migration in vitro and tumor formation in vivo. Results: The inhibition of PGRN/GP88 action by fully human monoclonal antibodies inhibited cell proliferation and migration in a dose-and time-dependent fashion. Octet analysis determined Kd in the range of 10−11 M to 10−10 M. Transwell assay showed that anti-PGRN treatment inhibited migration of non-small cell lung cancer cells such as H1299 and A549 cells. In vivo xenograft studies with H1299 cells injected in athymic nude mice showed that fully human anti-PGRN antibodies inhibited tumor growth when compared to antibody control treated mice. Conclusion: PGRN/GP88 represents a therapeutic target for non-small cell carcinoma with two companion diagnostics (tissue test and ELISA to measure GP88 circulating levels). The use of the TC transgenic mice allows for the rapid development of fully human high affinity monoclonal antibodies bypassing the need for chimerization or humanization and affinity maturation of monoclonal antibodies raised in mice or other humanized systems. This work is supported by SBIR grants R44 CA 224718 and R44CA162729 from the National Cancer Institute to GS. Citation Format: Ginette Serrero, Jianping Dong, Binbin Yue, Mitsuo Oshimura, Chun Dong, Jun Hayashi. New generation of fully human anti-progranulin monoclonal antibodies inhibiting migration and tumor formation of non-small cell carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1864.

Abstract The human epidermal growth factor receptor (HER) family of receptors plays a key role in proliferation stimulator for several human cancers. In particular, HER2 is overexpressed in 15-30% of breast cancers with or without gene amplification with prognostic and predictive implications. HER2 overexpression is associated with shorter disease-free and overall survivals, resistance to hormonal agents and increased risk of brain metastasis. Trastuzumab is a humanized anti-HER2 monoclonal antibody that binds to domain IV of HER2 extracellular domain and blocks its signaling. More recently, two antibody drug conjugates using trastuzumab have been approved: Ado-Trastuzumab-Emtansine (Kadcyla) consisting of trastuzumab conjugated to the drug mertansine DM1 and fam-trastuzumab-deruxtecan-nhki (Enhertu to deliver the topoisomerase inhibitor deruxtecan. We are reporting here the development of fully human internalizing anti-HER2 antibodies with distinct epitopes on the HER2protein which compete or not with trastuzumab for binding to HER2. These monoclonal antibodies have been developed by immunizing fully human (TC-Mab mouse) mice with recombinant HER2 protein. After production of hybridoma secreting fully human immunoglobulins, the screening process included competition with trastuzumab for binding to Her2 by enzyme linked immunoassay and Octet epitope binning and affinity determination as well as internalization assay. Several internalizing antibodies able to compete or not with trastuzumab and with high affinity (Kd ranging from 10−9 M to 10−12 M) were selected. Their ability to deliver a cytotoxic payload in HER2 overexpressing breast cancer cells such as SKBR3, BT474 and AU565 was next investigated. Two groups of antibodies: one competing with trastuzumab and the other one non-competing were further characterized. Data related to these antibodies’ biochemical characteristics as well as their ability to inhibit proliferation in vitro and in vivo in mouse xenografts studies will be presented here. In conclusion, the use of fully human mice to develop monoclonal antibodies provides a powerful and attractive approach to develop fully human monoclonal antibodies against cancer targets by-passing the need for humanization and affinity maturation of antibodies. This work is supported by 5R44CA224718 SBIR grant from the National Cancer Institute. Citation Format: Ginette Serrero, Binbin Yue, Jianping Dong, Jun Hayashi. Combination of trastuzumab competing and non-competing fully human internalizing anti-Her2 monoclonal antibodies drug conjugates increases their inhibitory effect on the growth of HER2 positive metastatic breast cancer cells [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-04-02.

The human epidermal growth factor receptor (HER) family of receptors has been implicated in several human cancers. Among them, HER2 is overexpressed in several cancers with or without gene amplification with prognostic and predictive implications. In 15-30% of breast cancers, HER2 overexpression and amplification are associated with shorter disease-free and overall survivals along with resistance to hormonal agents as well as increased risk of brain metastasis. Two types of HER2 targeting have been developed: anti-HER2 monoclonal antibodies and small molecule tyrosine kinase inhibitors. Trastuzumab is a humanized anti-HER2 monoclonal antibody that binds to domain IV of HER2 extracellular segment and blocks its signaling. It is the first therapeutic antibody targeting Her2 overexpression approved by the FDA. More recently, two antibody drug conjugates using trastuzumab have been approved: Ado-Trastuzumab-Emtansine (Kadcyla) consisting of trastuzumab conjugated to the drug mertansine DM1 and fam-trastuzumab-deruxtecan-nhki (Enhertu to deliver the topoisomerase inhibitor deruxtecan. We are reporting here the development of fully human internalizing anti-Her2 antibodies that compete or not with trastuzumab for binding to Her2. These antibodies have been developed by immunizing fully human (TC-Mab mouse) mice with recombinant Her2 protein. After production of hybridoma secreting fully human immunoglobulins, the screening process included inhibition of binding of trastuzumab to Her2 by enzyme linked immunoassay and by Octet epitope binning as well as internalization assay. Several internalizing antibodies able to compete or not with trastuzumab and with high affinity (Kd ranging from 10−9 M to 10−12 M) were selected. They were next investigated for their ability to deliver a cytotoxic payload in HER2 overexpressing cells breast cancer cells such as SKBR3, BT474 and AU565. Two antibodies: one competing with trastuzumab and the other one non-competing were further characterized. Data related to these antibodies’ biochemical characteristics as well as their ability to inhibit proliferation in vitro and in vivo in mouse xenografts studies will be presented here. In conclusion, the use of fully human mice in our laboratory provides a powerful and attractive approach to develop fully human monoclonal antibodies against cancer targets allowing to by-pass the need for humanization and affinity maturation of antibodies. Citation Format: Ginette Serrero, Binbin Yue, Jianping Dong, Chun Dong, Jun Hayashi. Development of competing and non-competing fully human internalizing anti-Her2 monoclonal antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 561.

The human epidermal growth factor receptor (HER) family of receptors plays a significant role in the pathogenesis of several human cancers. Among them, HER2 is overexpressed in several cancers. In particular, overexpression with or without gene amplification occurs in 15-30% of breast cancers and this has both prognostic and predictive implications. HER2 overexpression and amplification is associated with shorter disease-free and overall survivals and with resistance to certain hormonal agents as well as increased risk of metastasis to the brain. Two types of treatment targeting HER2 biological activity have been developed: anti-Her2 monoclonal antibodies and small molecule tyrosine kinase inhibitors such as lapatinib and neratinib targeting HER2 and EGFR and Afatinib targeting all HER family members. Trastuzumab is a humanized anti-HER2 monoclonal antibody that binds to domain IV of HER2 extracellular segment and blocks its signaling. It is the first therapeutic antibody targeting Her2 overexpression approved by the FDA. It is administered in combination with standard of care chemotherapy. More recently, since it was shown that Trastuzumab was an internalizing antibody, two antibody drug conjugates using trastuzumab have been approved and used in the standard of care: Ado-Trastuzumab-Emtansine (Kadcyla) consisting of trastuzumab conjugated to the drug mertansine DM1 and fam-trastuzumab-deruxtecan-nhki (Enhertu). Enhertu is another antibody drug conjugate using Trastuzumab to deliver a topoisomerase inhibitor deruxtecan. Our laboratory has been focused in developing fully human internalizing anti-Her2 antibodies that compete or not with trastuzumab for binding to Her2. These antibodies have been developed by immunizing fully human mice with recombinant Her2 protein. Human Ab producing Tc mice (TC-mAb mice) stably maintain a mouse-derived engineered chromosome containing the entire human Ig heavy and kappa chain loci in a mouse Ig knockout background. After production of hybridoma secreting fully human immunoglobulins, the screening process included inhibition of binding of trastuzumab to Her2 by enzyme linked immunoassay and by Octet epitope binning as well as internalization assay. Several internalizing antibodies with Kd ranging from 10-9 M to 10-12 M were selected. They were stratified by their ability to compete or not with trastuzumab. They were further characterized for their ability to deliver a cytotoxic payload in Her2 overexpressing cells as well as for their efficacy to inhibit proliferation, signaling and migration of Her2 overexpressing breast cancer cells. Data related to these antibodies will be presented here. In conclusion, the use of fully human TC mice in our laboratory represents an attractive approach to develop fully human monoclonal antibodies to high value cancer targets that can by-pass the need for humanization and affinity maturation of antibodies. Citation Format: Ginette Serrero, Jianping Dong, Binbin Yue, Udaya Yerramalla, Jun Hayashi. Characterization of fully human internalizing anti-HER2 monoclonal antibodies that compete with Trastuzumab for binding to HER2 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-19-01.

The ability to monitor response to therapy and disease progression in metastatic breast cancer (MBC) patients is a major step in patient management. Imaging is the method of choice for the assessment of disease status and the monitoring of disease progression. However, this approach remains expensive, expose patients to radiation and thus is mainly performed every 2-3 months. During this time interval, the disease may progress significantly on ineffective treatment and the patient may present treatment related toxicities due to the inability to detect progression at earlier times. Circulating levels of tumor associated biomarkers such as CA15-3 and CEA are often determined to track disease status of MBC. However, even though they can provide information about disease progression, they do not always provide a reliable measure of response to therapy. The monitoring of disease status and progression through the measurement of drivers of disease should provide an alternative and complementary approach to existing strategies in order to better to monitor the disease status and enable proactive management of MBC patients. Progranulin also called Glycoprotein 88kDa (PGRN/GP88) is an autocrine growth factor overexpressed in breast cancer. Biological studies have established GP88 as a critical player in breast tumorigenesis. GP88 overexpression is associated with the malignant phenotype, estrogen independence, increased proliferation, survival, and drug resistance. High PGRN/GP88 tumor expression measured by immunohistochemistry in invasive ductal carcinoma is an independent prognostic marker associated with increased risk of recurrence and mortality. Clinical studies have demonstrated that GP88 circulating levels as measured by enzyme immunoassay are elevated in breast cancer patients, compared to healthy individuals. In MBC patients, circulating GP88 levels correlate with overall survival. These facts are supportive of the hypothesis that the measurement of circulating GP88 levels in MBC patients can serve as an additional biomarker to monitor MBC disease status and be predictive to outcome. A prospective study was established is to identify whether there is a statistically significant change in serum GP88 levels associated with time to progression of breast cancer as measured by RECIST 1.1 criteria in MBC patients. With the assumptions that patients will provide a baseline and four follow up visits and that 20% of the visits record a disease progression, time to progression. Taking the plausible and clinically relevant performance to be 75% sensitivity and 46% false positive, a sample of ninety patients would give 85% power. Under IRB approved protocols at the University of Maryland Greenebaum Comprehensive Cancer Center and at two Baltimore Medstar Health Facilities, a total of 103 female breast cancer patients with measurable or evaluable metastatic disease will be consented and enrolled. The patients have been re-staged within 4 weeks and will continue or begin new therapy. Currently, we have enrolled sixty-five subjects at the three facilities. In addition to standard laboratory assessment and radiographic imaging/staging every 2-3 months on study, blood samples will be collected from each patient. The samples are stored at -70C until evaluated for GP88 using a GP88 enzyme linked immunoassay. We will analyze the GP88 serum level in correlation with survival and with disease status determined as responder, stable or progressing based on the RECIST criteria. This study is supported by grant R44CA210817 from the National Cancer Institute to Ginette Serrero Principal Investigator. Citation Format: Ginette Serrero, Paula Rosenblatt, Nancy Tait, Barbara Rector, Jennifer A. Latteri, Binbin Yue, Katherine Tkaczuk. On-going prospective study to measure serum progranulin/GP88 levels in metastatic breast cancer patients in association with disease status [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-16-01.

Progranulin (PGRN/GP88) is an 88 kDa glycoprotein characterized by seven and a half double cysteine rich repeats in the granulin-epithelin family. PGRN/GP88 is an autocrine biological driver of tumorigenesis, survival & drug resistance in several cancers including breast, ovarian, multiple myeloma, prostate cancers, non-small cell lung carcinoma (NSCLCA) & digestive cancers. PGRN/GP88 tissue expression is an independent prognostic factor of recurrence while elevated serum PGRN/GP88 level in metastatic breast, lung & prostate cancer patients is associated with poor outcomes such as progression & shortened survival. An anti-human PGRN/GP88 monoclonal antibody inhibiting PGRN/GP88 action has been developed & expressed as recombinant antibody in CHO cells. Activities including pharmacology, manufacturing, formulation & GLP toxicology studies have been carried out. The IND application has been cleared by the Food and Drug Administration to proceed with the first-in-human AG01 clinical study in adult patients ((pts) with advanced solid tumors. We present an ongoing First in Human Phase 1A (dose escalation,1+(3+3) & IB (expansion cohorts) study of AG01 in pts advanced solid tumor malignancies (1A) with 4 expansion cohorts (1B) in pts with advanced Triple Negative Breast Cancer (TNBC), Hormone Resistant ER+/Her2- BC, advanced NSCLC & mesothelioma. Study Design: This is an open-label, dose escalation study of AG01 antibody administered intravenously (IV) over 90 minutes every 14 days +/- 1 day (1A), followed by 4 predefined expansion cohorts, which will be treated at the RP2D determined in the phase 1A of this study. In the 1A part, initially accelerated titration design will be utilized to guide dose progression & estimation of the maximum tolerated dose (MTD and/or maximum administered dose (MAD). In the 1A portion of the study pts with advanced relapsed/refractory solid tumor malignancies who failed 1 or more standard of care (SOC) therapies (tx) or for whom no SOC tx exists will be accrued. The primary objective of the 1A part is to determine the MTD and/or MAD of AG01. Secondary objectives are to determine the RP2D, assess the safety/tolerability, the pharmacokinetics (PKs) & immunogenicity of AG01 & the preliminary anti-tumor activity of AG01 via RECIST 1.1. The exploratory objectives are to determine PGRN/GP88 expression in tumor tissue and PGRN/GP88 blood levels using A&G’s ELISA test. In the 1B Cohort Expansion phase, 4 separate cohorts of pts with PGRN/GP88 tissue expression of 1+, 2+, 3+ by IHC will be enrolled. Cohort 1- TNBC: ER and/or PR < 1% by IHC, HER2 < 3+ by IHC and/or FISH negative, pts must have failed 1 or more SOC tx for metastatic BC. Cohort 2- Hormone-resistant BC: ER and/or PR >1%, HER2 < 3+ by IHC and/or FISH negative, failed 1 or more prior hormonal tx (HT) or HT/CD4/6 kinase inhibitor tx or other targeted tx. Cohort 3- NSCLCA: metastatic/recurrent NSCLCA failed 2 or more SOC tx. Cohort 4 -Mesothelioma- failed 1 or more SOC tx for metastatic/recurrent mesothelioma or not a candidate for SOC tx. The primary objective of 1B part is to evaluate the antitumor efficacy of AG01 by overall response rate (ORR) defined as completed response (CR), partial response (PR), stable disease >=24 weeks (SD) (CR+PR+ SD) based on RECIST v1.1 in the 4 cohorts with each cohort assessed separately for response. Secondary objectives are to evaluate progression free survival (PFS), duration of response (DOR) & overall survival (OS) of pts in cohorts 1-4, & to evaluate the ORR, DOR & PFS based on GP88 tissue expression, to further characterize the PKs & the safety/tolerability of AG01. Exploratory objectives in 1B part will assess AG01 effect on circulating PGRN/GP88 levels in plasma or other potential biomarkers in the 4 cohorts. The estimated study sample is approximately 77 pts; 17 pts for the 1A part & 60 pts for 1B part. The study is open to accrual at the UMGCCC. Supported by NCI grants R44CA224718 and R44CA162629 Citation Format: KATHERINE TKACZUK, Paula Rosenblatt, Ranee Mehra, Katherine Scilla, Nancy Tait, Binbin Yue, Ginette Serrero. First in Human Study of AG01 a chimerized monoclonal antibody to Progranulin/Glycoprotein 88 (GP88) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-13-01.

Progranulin (PGRN/GP88) is an 88 kDa glycoprotein characterized by seven and a half double cysteine rich repeats which is the largest member of the granulin-epithelin protein family. PGRN/GP88 has been demonstrated as a biological driver of tumorigenesis, survival, and drug resistance in several cancers including breast cancer (BC), lung prostate, ovarian and digestive cancers. PGRN/GP88 tissue expression is an independent prognostic factor of recurrence in breast, lung cancers while elevated serum PGRN/GP88 level in metastatic breast, lung, ovarian and prostate cancer patients. Elevated PGRN/GP88 levels are associated with poor outcomes such as progression and shortened survival. An anti-human PGRN/GP88 monoclonal antibody able to inhibit PGRN/GP88 action in vitro and in vivo has been developed, chimerized and expressed in CHO cells. All IND enabling activities including pharmacology, GMP manufacturing, formulation and GLP toxicology studies have been conducted. The IND application has been filed and cleared by the Food and Drug Administration. A first-in-human, first-in-class phase 1 safety and efficacy clinical study of AG01 in patients with solid tumors and advanced disease with special focus on patients with breast, lung and ovarian cancers has been initiated and is on-going at the University of Maryland Greenebaum Cancer Center. The trial is registered as NCT05627960 to clinicaltrials.gov site. Supported by grants R44CA162629 and R44CA224718 from the National Cancer Institute to GS. Citation Format: Katherine R. Tkaczuk, Paula Rosenblatt, Ranee Mehra, Katherine A. Scilla, Nancy Tait, Katerra Caple, Binbin Yue, Ginette Serrero. On-going phase 1A clinical trial for AG01 an first-in-class anti-progranulin (GP88) monoclonal antibody in patients with advanced malignancies [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 CT240.

Background: Triple negative breast cancer (TNBC) is characterized by invasiveness and short survival. Identifying novel TNBC targeted therapies to potentiate standard of care (SOC) therapy, is an unmet need. Progranulin (PGRN/GP88) is a biological driver of tumorigenesis, survival, and drug resistance in several cancers including breast cancer (BC). PGRN/GP88 tissue expression is an independent prognostic factor of recurrence while elevated serum PGRN/GP88 level is associated with poor outcomes such as progression of disease and shortened survival. Since PGRN/GP88 expression is elevated in 30% TNBC, we investigated the effect of inhibiting PGRN/GP88 effect on the proliferation and tumor growth of triple negative breast cancer cells. Methods: For this purpose, we have developed a neutralizing anti-human PGRN/GP88 monoclonal antibody AG01 and examined its effect on the proliferation, migration, signaling pathway activation and biomarker expression of two TNBC cell lines MDA-MB-231 and HS578-T expressing PGRN/GP88, both in vitro and in vivo. Results: The inhibition of PGRN/GP88 action by AG01 treatment reduced proliferation and migration in a dose-and time-dependent fashion in MDA-MB-231 and HS578-T cells. Western blot analysis showed decreased expression of phosphorylated protein kinases p-Src, p-AKT and p-ERK involved in proliferation and survival upon AG01 treatment for both cell lines. Transwell assay showed that AG01 treatment inhibited migration and invasion in a dose-dependent fashion. Microarray analysis of several oncoproteins in cells treated with AG01 or control antibody demonstrated the inhibition of the expression of several markers of migration and angiogenesis. In vivo xenograft studies with MDA-MB-231 cells injected in athymic nude mice showed that AG01 treatment inhibited tumor growth as well as Ki67 expression, mitotic index and microvessel counts when compared to antibody control treated mice. In vivo dose response of AG01 in MDA-MB-231 tumor bearing mice will be provided. Conclusion: TNBC is a disease with poor prognosis in need of novel targeted therapeutic solutions. PGRN/GP88 represents a therapeutic target for TNBC with two companion diagnostics (tissue test and ELISA to measure GP88 circulating levels). Blocking PGRN/GP88 with AG01 antibody treatment will provide novel targeted therapeutic option for TNBC which could address the issue of toxicity, and unresponsiveness associated with SOC. This work is supported by a grant CA 224718 from the National Cancer Institute to GS. Citation Format: Ginette Serrero, Rupa Guha, Jianping Dong, Binbin Yue. Anti-progranulin (GP88) antibody AG01 inhibitory effect on the growth of triple negative breast cancer cells [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-17-10.