Quantitative Analysis of Serial Positron Emission Tomography Imaging in Men with Metastatic Castration-resistant Prostate Cancer Treated with Enzalutamide

BACKGROUND

The emergence of positron emission tomography (PET) in prostate cancer is impacting clinical practice, but little is known about PET imaging as a tool to determine treatment failure in metastatic castration-resistant prostate cancer (mCRPC).

OBJECTIVE

To evaluate PET imaging dynamics in mCRPC patients on enzalutamide with stable computed tomography (CT) and technetium-99m (Tc99) bone scans.

DESIGN, SETTING, AND PARTICIPANTS

All patients were on treatment with enzalutamide for first-line mCRPC in a clinical trial at the National Cancer Institute (Bethesda, MD, USA). A volunteer sample had serial 18F-sodium fluoride (NaF) PET in parallel with CT and Tc99. Regions of interest (ROIs) on NaF were analyzed quantitatively for response.

INTERVENTION

Patients were randomized to enzalutamide with/without a cancer immunotherapy, Prostvac.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

A post hoc, descriptive analysis was performed comparing the changes seen on CT and Tc99 as per RECIST 1.1 with NaF PET scans including the use of a quantitative analysis.

RESULTS AND LIMITATIONS

Eighteen mCRPC patients had 67 NaF scans. A total of 233 ROIs resolved after treatment, 52 (22%) of which eventually retuned while on therapy. In all, 394 new ROIs were seen, but 112(28%) resolved subsequently. Of 18 patients, 14 had new ROIs that ultimately resolved after appearing. Many patients experienced progression in a minority of lesions, and one patient with radiation intervention to oligoprogression had a remarkable response. This study is limited by its small number of patients and post hoc nature.

CONCLUSIONS

These data highlight the dynamic nature of NaF PET in mCRPC patients treated with enzalutamide, where not all new findings were ultimately related to disease progression. This analysis also provides a potential strategy to identify and intervene in oligoprogression in prostate cancer.

PATIENT SUMMARY

In this small analysis of patients with prostate cancer on enzalutamide, changes on 18F-sodium fluoride positron emission tomography (PET) imaging were not always associated with treatment failure. Caution may be indicated when using PET imaging to determine whether new therapy is needed.

Flutamide With or Without PROSTVAC in Non-metastatic Castration Resistant (M0) Prostate Cancer

BACKGROUND

Before 2018, there was no standard of care for non-metastatic (M0) castration resistant prostate cancer nmCRPC. Androgen receptor antagonists (ARAs) were commonly used sequentially nmCRPC.

METHODS

This was a multicenter, randomized clinical trial comparing the ARA flutamide+/-PROSTVAC, a pox viral vaccine targeting PSA that includes T-cell co-stimulatory molecules. Eligible men had negative CT and Tc99 bone scans, and rising PSA on ADT. Previous treatment with ARA was a stratification factor. Patients were also evaluated for antigen-specific immune responses using intracellular cytokine staining.

RESULTS

Thirty-three patients randomized to flutamide and 31 to flutamide+vaccine. The median age was 71.8 and 69.8 years, respectively. The median time to treatment failure after a median potential follow-up of 46.7 months was, 4.5 months (range 2-70) for flutamide alone vs. 6.9 months (2.5-40; P = .38) with flutamide+vaccine. Seven patients in each arm had a >50% PSA response. Antigen-specific responses were similar in both arms (58% of patients in flutamide alone and 56% in flutamide+vaccine). The treatments were well tolerated. The most common side effect > grade 2 was injection site reaction seen in 29/31 vaccine patients which were self-limiting.

CONCLUSION

The combination of flutamide+PROSTVAC did not improve outcomes in men with nmCRPC compared with flutamide alone. (ClinicalTrials.gov Identifier: NCT00450463).

Abstract 5654: A therapeutic humanized anti-carcinoma monoclonal antibody (mAb) NEO-201 can also target human granulocytic myeloid-derived suppressor cells (gMDSCs) and regulatory T (Tregs) cells

Background: NEO-201 is a humanized IgG1 mAb reactive against multiple human cancers but not against most normal epithelial tissues. NEO-201 binds to core 1 or extended core 1 O-glycans expressed by its target cells, including neutrophils, various carcinomas, and some human hematological malignancies. NEO-201 can mediate antitumor activity through antibody-dependent cellular cytotoxicity (ADCC), complement dependent cytotoxicity (CDC), and blockade of the CEACAM5/CEACAM1 ICI pathway. A previous study using flow cytometry demonstrated that NEO-201+/CD4+ T cells were also CD25+/CD127−/Foxp3+/CD15s+ using PBMCs from healthy donors (HD). NEO-201 can kill these Treg cells through CDC in vitro. NEO-201 does not bind to the majority of CD4+ T cells and to other immune subsets. Human gMDSCs are increased in cancer patients and are a population of immature MDSCs deriving from immature neutrophils and alternative activation of mature neutrophils. gMDSC are characterized by HLA-DR−, CD11b+, CD33+, CD15+phenotype.We have shown that NEO-201 recognizes and kill human neutrophils through ADCC. This current investigation was designed to evaluate whether NEO-201 can target and mediate ADCC activity against human gMDSCs.

Methods: gMDSCs were generated from human neutrophils from 5 HD isolated using EasySepTM direct human neutrophil isolation kit. Isolated neutrophils were cultured in complete RPMI1640 medium supplemented with human GM-CSF and human IL-6 for 7 days. Phenotypic analysis by flow cytometry was performed on the generated gMDSCs using NEO-201 and mAbs against human CD33, HLA-DR, CD15, CD14, CD66b. Flow cytometry based ADCC assay was performed using gMDSCs stained with both CD33 and HLA-DR as target. PBMCs from a separate HD were used as effectors at different E:T ratios. The ADCC activity of NEO-201 was evaluated comparing the percentage of CD33+/HLA-DR− viable cells in gMDSCs incubated with medium alone to the percentage of CD33+/HLA-DR− viable cells incubated with PBMCs alone and with PBMCs plus NEO-201.

Results: Flow cytometry analysis revealed that gMDSCs can be generated from human neutrophils after 7 days of culture with GM-CSF and IL-6 and that they express the following phenotype: HLA-DR−/CD33+/CD15+/CD14−/CD66b+. NEO-201 bound to the majority of these gMDSCs. NEO-201 was functional in mediating ADCC to kill these gMDSCs.

Conclusion: This study demonstrated that NEO-201 can be used to identify and kill suppressive gMDSCs in addition to Treg cells. Depletion of suppressive Tregs and gMDSCs in the TME could be an effective strategy to prevent hyperprogressive disease when anti-PD-1 is used in cancer immunotherapy. These data support the rationale for the ongoing phase II clinical trial using NEO-201 in combination with pembrolizumab in checkpoint refractory patients with metastatic solid tumors.

Citation Format: Massimo Fantini, Christina M. Annunziata, Philip M. Arlen, Kwong Y. Tsang. A therapeutic humanized anti-carcinoma monoclonal antibody (mAb) NEO-201 can also target human granulocytic myeloid-derived suppressor cells (gMDSCs) and regulatory T (Tregs) cells. [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 5654.

First-in-human phase 1 clinical trial of anti-core 1 O-glycans targeting monoclonal antibody NEO-201 in treatment-refractory solid tumors

BACKGROUND

NEO201 is a humanized IgG1 monoclonal antibody (mAb) generated against tumor-associated antigens from patients with colorectal cancer. NEO-201 binds to core 1 or extended core 1 O-glycans expressed by its target cells. Here, we present outcomes from a phase I trial of NEO-201 in patients with advanced solid tumors that have not responded to standard treatments.

METHODS

This was a single site, open label 3 + 3 dose escalation clinical trial. NEO-201 was administered intravenously every two weeks in a 28-day cycle at dose level (DL) 1 (1 mg/kg), DL 1.5 (1.5 mg/kg) and DL 2 (2 mg/kg) until dose limiting toxicity (DLT), disease progression, or patient withdrawal. Disease evaluations were conducted after every 2 cycles. The primary objective was to assess the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of NEO-201. The secondary objective was to assess the antitumor activity by RECIST v1.1. The exploratory objectives assessed pharmacokinetics and the effect of NEO-201 administration on immunologic parameters and their impact on clinical response.

RESULTS

Seventeen patients (11 colorectal, 4 pancreatic and 2 breast cancers) were enrolled; 2 patients withdrew after the first dose and were not evaluable for DLT. Twelve of the 15 patients evaluable for safety discontinued due to disease progression and 3 patients discontinued due to DLT (grade 4 febrile neutropenia [1 patient] and prolonged neutropenia [1 patient] at DL 2, and grade 3 prolonged (> 72 h) febrile neutropenia [1 patient] at DL 1.5). A total of 69 doses of NEO-201 were administered (range 1-15, median 4). Common (> 10%) grade 3/4 toxicities occurred as follows: neutropenia (26/69 doses, 17/17 patients), white blood cell decrease (16/69 doses, 12/17 patients), lymphocyte decrease (8/69 doses, 6/17 patients). Thirteen patients were evaluable for disease response; the best response was stable disease (SD) in 4 patients with colorectal cancer. Analysis of soluble factors in serum revealed that a high level of soluble MICA at baseline was correlated with a downregulation of NK cell activation markers and progressive disease. Unexpectedly, flow cytometry showed that NEO-201 also binds to circulating regulatory T cells and reduction of the quantities of these cells was observed especially in patients with SD.

CONCLUSIONS

NEO-201 was safe and well tolerated at the MTD of 1.5 mg/kg, with neutropenia being the most common adverse event. Furthermore, a reduction in the percentage of regulatory T cells following NEO-201 treatment supports our ongoing phase II clinical trial evaluating the efficiency of the combination of NEO-201 with the immune checkpoint inhibitor pembrolizumab in adults with treatment-resistant solid tumors.

TRIAL REGISTRATION

NCT03476681 . Registered 03/26/2018.

Effects of docetaxel on circulating immune cell subsets and association with outcomes in metastatic castration-sensitive prostate cancer

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Background: Docetaxel with androgen deprivation therapy (ADT) has been shown to improve survival in metastatic castration-sensitive prostate cancer (mCSPC). There is limited data on the immunologic effects of docetaxel in mCSPC. Greater knowledge of the immune impact of docetaxel could inform future trials in prostate cancer. Methods: A clinical trial in mCSPC evaluated sequencing docetaxel and ADT with Prostvac, a poxviral vaccine targeting prostate-specific antigen (PSA). Eligibility criteria included mCSPC within 4 months of ADT and ECOG performance status 0-2. Patients given 6 cycles of docetaxel 75mg/m2 with ADT alone for mCSPC were included in this analysis. Peripheral blood mononuclear cells (PBMCs) were sampled at baseline and at 3 weeks after commencing docetaxel. Immune cell subsets analyzed included CD4+ and CD8+ T-cells, T regulatory cells (Tregs), natural killer (NK) cells, dendritic cells (DCs) and myeloid-derived suppressor cells (MDSCs). Analyses were performed to determine if the baseline immune status or immune changes induced by therapy associate with PSA at 2 years. Results: Fifteen patients were evaluated for peripheral immune responses in this study. Median age was 63 years (range 50-73). Fourteen were white and 1 was black. ECOG performance status was 0 in 11 patients, 1 in 4 patients. Disease volume was high in 7 and low in 8 patients. Among 158 immune cell subsets assessed, only changes in Tregs and activated NK cells with a lytic and cytokine producing phenotype (CD16+ CD56br) were noted after initiation of docetaxel in addition to ADT. Patients with PSA ≤0.2 at 2 years had higher baseline frequencies of total CD4+ T cells, several activated CD4+ T-cell subsets, plasmacytoid DCs, and CD49d- Tregs. They also had lower baseline frequencies of total CD8+ T cells, naïve CD8+ T cells, and CD73+CD8+ T-cells. Patients with PSA ≤0.2 at 2 years also had greater percent increases in CD8+ effector memory (EM) PD-1+ T-cells after treatment. Conclusions: This is the first study to demonstrate increases in activated NK cells with lytic and cytokine producing potential after treatment with docetaxel. Given that NK cells are associated with clinical outcomes in prostate cancer (Zhao SG, JNCI, 2019) and that increased NK cells were seen after treatment with enzalutamide as well (Madan, JITC, 2021), developing immunotherapy combinations to capitalize on NK cell activity may be a path forward for developing immunotherapy in prostate cancer. Clinical trial information: NCT02649855 . [Table: see text]

Identification of the O-Glycan Epitope Targeted by the Anti-Human Carcinoma Monoclonal Antibody (mAb) NEO-201

Simple Summary

Glycosylation is an important post-translational modification made on mammalian proteins and lipids. In cancer cells, the disruption of several glycosylation patterns, such as the O-glycosylation, has been observed. The expression of incomplete/truncated O-glycans in cancer cells occurs in both solid and liquid tumors and is correlated with poor prognosis and tumor progression. The employment of monoclonal antibodies (mAbs) targeting truncated O-glycans in cancer cells could serve as an effective strategy to counteract tumor growth. In previous studies, we reported that the IgG1-humanized mAb NEO-201 binds specifically to tumor-associated variants of CEACAM5 and CEACAM6 expressed by colon, ovarian, pancreatic, non-small cell lung, head and neck, cervical, uterine and breast cancers but is not reactive against most normal tissues. Since CEACAMs are highly glycosylated proteins, in this article, we evaluated whether the epitope recognized by NEO-201 is an O-glycan. This study demonstrated that NEO-201 binds to core 1 O-glycans and targets and kills cancer cells expressing core 1 and extended core 1 O-glycans. Usually, GalNAc residue can be added on to threonine and serine to form O-glycans, suggesting that NEO-201 binds to core 1 and extended core 1 O-glycans attached to any protein carrying amino acid regions containing serine and threonine

Abstract

Truncated O-glycans expressed in cancer cells support tumor progression, and they may serve as potential targets to improve the monitoring and treatment of cancers. Previously, we reported that NEO-201 binds to several tumors expressing tumor-associated CEACAM5 and CEACAM6 variants but does not bind to those expressed in healthy tissues. This specific binding may be associated with the presence of truncated O-glycans attached on the protein sequence of these variants. To evaluate the glycosylation pattern targeted by NEO-201 we performed an O-glycan array consisting of 94 O-glycans. O-glycan profiles were elucidated from the human pancreatic cancer cell line CFPAC-1, human hematological neoplastic cells (HL-60, U937, K562) and human neutrophils. The O-glycan array analysis showed that NEO-201 interacts with core 1-4 O-glycans and that the binding to a specific core 1 O-glycan was the strongest. The O-glycan profiling of the NEO-201-reactive cells CFPAC-1, HL-60, U937 and human neutrophils showed that cells recognized by NEO-201 express mostly core 1 and/or extended core 1 O-glycans. In addition, NEO-201 mediates antibody-dependent cell-mediated cytotoxicity (ADCC) against tumor cells expressing core 1 or extended core 1 O-glycan profiles. These results demonstrated that NEO-201 binds to core 1 and extended core 1 O-glycans expressed in its target cells. Since GalNAc residue can be added onto threonine and serine to form O-glycans, it is very likely that NEO-201 recognizes these O-glycans attached to any protein with amino acid regions containing serine and threonine.

Development and Characterization of an Anti-Cancer Monoclonal Antibody for Treatment of Human Carcinomas

NEO-201 is an IgG1 humanized monoclonal antibody (mAb) that binds to tumor-associated variants of carcinoembryonic antigen-related cell adhesion molecule (CEACAM)-5 and CEACAM-6. NEO-201 reacts to colon, ovarian, pancreatic, non-small cell lung, head and neck, cervical, uterine and breast cancers, but is not reactive against most normal tissues. NEO-201 can kill tumor cells via antibody-dependent cell-mediated cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC) to directly kill tumor cells expressing its target. We explored indirect mechanisms of its action that may enhance immune tumor killing. NEO-201 can block the interaction between CEACAM-5 expressed on tumor cells and CEACAM-1 expressed on natural killer (NK) cells to reverse CEACAM-1-dependent inhibition of NK cytotoxicity. Previous studies have demonstrated safety/tolerability in non-human primates, and in a first in human phase 1 clinical trial at the National Cancer Institute (NCI). In addition, preclinical studies have demonstrated that NEO-201 can bind to human regulatory T (Treg) cells. The specificity of NEO-201 in recognizing suppressive Treg cells provides the basis for combination cancer immunotherapy with checkpoint inhibitors targeting the PD-1/PD-L1 pathway.

Combining IL-12 immunocytokine (M9241) with docetaxel in metastatic prostate cancer: A phase I study

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Background: M9241 is an immunocytokine that targets single- and double-stranded DNA which allows the treatment to localize IL-12 to necrotic tumor (Xu, CCR 2017). M9241 was well-tolerated as a monotherapy in a Phase I study with solid tumors (Strauss J, CCR 2019). Additional preclinical data has demonstrated synergy of M9241 with cytotoxic therapy. This is the first study to examine the safety of a novel combination of chemotherapy and immunocytokines in metastatic prostate cancer. Methods: This safety analysis included patients with mCSPC or mCRPC. Patients were enrolled in a 2-dose level (DL) escalation cohort of M9241 (DL 1: 12mcg/kg, DL 2: 16.8mcg/kg) combined with docetaxel (75mg/m2) with 6 patients planned per DL. A third DL of 8mcg/kg will enroll 6 more patients after the 16.8mcg/kg DL has fully enrolled. All patients were treated with ADT. Patients were initiated on treatment with docetaxel with a plan for mCSPC patients to receive six 3-week cycles of combined treatment and mCRPC patients to continue until progression or unacceptable toxicity. M9241 was given starting with the second cycle of treatment for each patient. Dose-limiting toxicity (DLT) was evaluated in the first 6 weeks after start of docetaxel (from cycle 1 day 1 through the end of the first cycle with M9241). Results: The study has enrolled 10 patients out of a planned 18 for the safety portion. Age range is 58-82 with a median of 69 years. Race distribution is 80% White and 20% Black. Gleason scores for patients were 8 (40%), 9 (40%), and 10 (20%). No DLTs were seen with either dose-level. Only 1 patient had a Grade 4 AE, neutropenia. Grade 3 toxicities included anemia, diarrhea, leukopenia, and hypotension (each occurring in 10% of the patients). The most frequent adverse events (AEs) of any grade were anemia (40%) and lymphopenia (40%), followed by fatigue (30%), diarrhea (20%), and fever (20%). Conclusions: We established a safe dose-level of M9241 at ≥ 12mcg/kg. Updated clinical data from the safety cohort (n = 18) will be presented. This demonstrates that an immunocytokine and chemotherapy can be safely combined for treatment in metastatic prostate cancer. Two planned expansion cohorts will evaluate docetaxel and M9241 in mCSPC and mCRPC, respectively. Clinical trial information: NCT04633252.

Evaluating the optimal sequence of immunotherapy and docetaxel in men with metastatic castration-sensitive prostate cancer

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Background: Docetaxel is a standard of care for metastatic castration-sensitive prostate cancer (mCSPC). PROSTVAC is a pox viral-based therapeutic cancer vaccine encoding for PSA and three T-cell co-stimulatory molecules. Pox viral-based vaccines had previously demonstrated potential immune synergy with docetaxel. This clinical trial evaluated the optimal sequence of immunotherapy and chemotherapy in mCSPC. Methods: Key eligibility criteria were mCSPC within 4 months of ADT and ECOG performance status 0-2. Patients were randomized between Arms A (6 cycles of docetaxel 75mg/m2 followed by 6 doses of PROSTVAC) and B (docetaxel concurrent with PROSTVAC). After rapid accrual to the first 2 arms, Arm C was added by protocol amendment (6 doses of PROSTVAC prior to 6 cycles of docetaxel). ADT was continued throughout the treatment period. The primary endpoint was to evaluate antigen-specific responses to the tumor antigens, PSA and MUC1, and brachyury, a transcription factor implicated in the metastatic process, after patients completed their respective sequence of docetaxel and PROSTVAC. This was done using intracellular cytokine staining of 4 established markers in both CD4+ and CD8+ T-cells, for a total of 8 measures of activation per antigen. Results: The study enrolled 73 patients with a median age of 63 years (range 41-86). Gleason scores for patients were 6 (4.1%), 7 (21.6%) and 8-10 (68.9%), with 5.4% being unknown. Median pre-ADT PSA was 34.75 ng/mL. Per CHAARTED criteria, disease volume was low in 41.1% and high in 58.9% of patients. Numbers of patients evaluable for immune responses in arms A, B, and C were 16, 12 and 18, respectively. Clinical responses have previously been presented (Atiq, MO et al., ASCO 2021), with 22% of all patients having PSA <0.2 at 2 years. Conclusions: This data provides some insights into the potential of immune activating therapies in relation to chemotherapy in patients with prostate cancer. This preliminary analysis suggests the greatest magnitude of immune activation is seen when immunotherapy is followed by chemotherapy. Additional analysis of the breadth of immune responses and associations with clinical outcomes is ongoing and will be presented. Clinical trial information: NCT02649855. [Table: see text]

Safety evaluation of M9241 in combination with docetaxel in metastatic prostate cancer

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Background: M9241 is an immunocytokine that targets single- and double-stranded DNA which allows the treatment to localize IL-12 to necrotic tumor (Xu, CCR 2017). M9241 was well-tolerated as a monotherapy in a Phase I study with solid tumors (Strauss J, CCR 2019). Additional preclinical data has demonstrated synergy of M9241 with cytotoxic therapy. This is the first study to examine the safety of a novel combination of chemotherapy and immunocytokines in metastatic prostate cancer. Methods: This safety analysis included patients with mCSPC or mCRPC. Patients were enrolled in a 2-dose level (DL) escalation cohort of M9241 (DL 1: 12mcg/kg, DL 2: 16.8mcg/kg) combined with docetaxel (75mg/m2) with 6 patients planned per DL. A third DL of 8mcg/kg will enroll 6 more patients after the 16.8mcg/kg DL has fully enrolled. All patients were treated with ADT. Patients were initiated on treatment with docetaxel with a plan for mCSPC patients to receive six 3-week cycles of combined treatment and mCRPC patients to continue until progression or unacceptable toxicity. M9241 was given starting with the second cycle of treatment for each patient. Dose-limiting toxicity (DLT) was evaluated in the first 6 weeks after start of docetaxel (from cycle 1 day 1 through the end of the first cycle with M9241). Results: The study has enrolled 10 patients out of a planned 18 for the safety portion. Age range is 58-82 with a median of 69 years. Race distribution is 80% White and 20% Black. Gleason scores for patients were 8 (40%), 9 (40%), and 10 (20%). No DLTs were seen with either dose-level. Only 1 patient had a Grade 4 AE, neutropenia. Grade 3 toxicities included anemia, diarrhea, leukopenia, and hypotension (each occurring in 10% of the patients). The most frequent adverse events (AEs) of any grade were anemia (40%) and lymphopenia (40%), followed by fatigue (30%), diarrhea (20%), and fever (20%). Conclusions: We established a safe dose-level of M9241 at ≥ 12mcg/kg. Updated clinical data from the safety cohort (n = 18) will be presented. This demonstrates that an immunocytokine and chemotherapy can be safely combined for treatment in metastatic prostate cancer. A planned expansion cohort will evaluate docetaxel and M9241 in mCRPC. Clinical trial information: NCT04633252.

Clinical and immunologic impact of short-course enzalutamide alone and with immunotherapy in non-metastatic castration sensitive prostate cancer

BACKGROUND

The standard treatment for non-metastatic castration sensitive prostate cancer (nmCSPC) is androgen deprivation therapy (ADT) or surveillance. This study evaluated the potential synergy of immunotherapy and enzalutamide (without ADT) in nmCSPC. In addition, the immunologic impact of enzalutamide was also evaluated in men with normal testosterone.

METHODS

Patients with rising prostate-specific antigen (PSA) after definitive therapy, normal testosterone and no radiographic metastasis were randomized to enzalutamide for 3 months with/without PROSTVAC for 6 months. Thereafter, patients could be retreated with another 3 month course of enzalutamide when PSA returned to baseline. Immune profiles were evaluated in these patients.

RESULTS

Thirty-eight patients were randomized with a median PSA=4.38 ng/dL and PSA doubling time=4.1 months. No difference was observed between the two groups for PSA growth kinetics, but PSA responses to enzalutamide were noteworthy regardless of PROSTVAC. The median PSA decline after short-course enzalutamide without ADT/testosterone lowering therapy was 99% in both courses. The median time to PSA recovery to baseline after each 84-day course of enzalutamide was also noteworthy because of the duration of response after enzalutamide was discontinued. After the first and second 3 month cycle of enzalutamide, PSA recovery to baseline took a median 224 (range 84-1246) and 189 days (78-400), respectively. The most common adverse events related to the enzalutamide were grade 1 fatigue (71%) and grade 1 breast pain/nipple tenderness (81%). The only grade 3 toxicity was aspartate aminotransferase (AST)/alanine aminotransferase (ALT) elevation in two patients. Enzalutamide was independently associated with immune changes, increasing natural killer cells, naïve-T cells, and decreasing myeloid-derived suppressor cells.

CONCLUSIONS

Three months of enzalutamide without ADT induced substantial PSA control beyond the treatment period and was repeatable, perhaps representing an alternative to intermittent ADT in nmCSPC. In addition, enzalutamide was associated with immune changes that could be relevant as future immune combinations are developed. TRAIL REGISTRATION NUMBER: clinicaltrials.gov (NCT01875250).

Cabozantinib plus docetaxel and prednisone in metastatic castration-resistant prostate cancer

OBJECTIVE

To evaluate the safety and efficacy of cabozantinib combined with docetaxel.

PATIENTS AND METHODS

This was a phase 1/2 multicentre study in patients with metastatic castration-resistant prostate cancer (mCRPC). Docetaxel (75 mg/m² every 3 weeks with daily prednisone 10 mg) was combined with escalating doses of daily cabozantinib (20, 40 and 60 mg). Based on the results of the phase 1 study, the investigation was expanded into a randomized study of docetaxel with prednisone (hereafter 'docetaxel/prednisone') plus the maximum tolerated dose (MTD) of cabozantinib compared with docetaxel/prednisone alone.

RESULTS

A total of 44 men with mCRPC were enrolled in this phase 1/2 trial. An MTD of 40 mg cabozantinib plus docetaxel/prednisone was determined. Dose-limiting toxicities were neutropenic fever and palmar-plantar erythrodysesthesia, and there was one death attributable to a thromboembolic event. In addition, grade 3 or 4 myelosuppression, hypophosphataemia and neuropathy were seen in three or more patients. In the phase 1 study, the median time to progression (TTP) and overall survival (OS) time were 13.6 and 16.3 months, respectively. In the phase 2 study, which was terminated early because of poor accrual, the median TTP and OS favoured the combination (n = 13) compared to docetaxel/prednisone alone (n = 12; 21.0 vs 6.6 months; P = 0.035 and 23.8 vs 15.6 months; P = 0.072, respectively).

CONCLUSION

Despite the limited number of patients in this study, preliminary data suggest that cabozantinib can be safely added to docetaxel/prednisone with possible enhanced efficacy.

Abstract 4534: A therapeutic humanized anti-carcinoma monoclonal antibody (mAb) can enhance NK activity and target immunosuppressive regulatory T cells

Background: NEO-201 is a therapeutic IgG1 humanized mAb reactive against many different carcinomas, but not reactive against most normal tissues. No reactivity was observed with NEO-201 in subsets of hematopoietic cells except CD15+ granulocytes. Functional analysis revealed that NEO-201 is capable of engaging in ADCC and CDC to kill tumor cells. Previous studies showed that NEO-201 attenuates growth of human tumor xenografts in mice and demonstrates safety/tolerability in non-human primates with a transient decrease in neutrophils being the only adverse effect observed. A first in human clinical trial evaluating NEO-201 in adults with chemo-resistant solid tumors is ongoing at the NIH clinical Center. NEO-201 recognizes tumor-associated variants of CEACAM5 and 6. CEACAM1 is a potent inhibitor of natural killer (NK) cell function; binding between CEACAM1 on NK cells and CEACAM1 or CEACAM5 on tumor cells inhibits activation signaling by NKG2D, which prevents NK cell cytolysis and permits tumor cells to evade NK killing. Preclinical evaluation showed that NEO-201 reacts against human regulatory T cells (Tregs). This study was designed to assess NK enhancing pathway and further investigated the phenotypic and functional effects of NEO-201 on human Tregs in vitro.

Materials & Methods: Various human tumor cell lines were used as target cells and NK-92 cells (CEACAM1+/CD16-) were used as effectors to assess the ability of NEO-201 to block the interaction between CEACAM5 on tumor cells and CEACAM1 on NK cells in order to enhance the in vitro killing of tumor cells. Phenotypic analysis was conducted by flow cytometry for Treg markers: CD4, CD25, CD127, FoxP3, CD15s, CD45RA, CCR4, NEO-201 antigen, CEACAM5 and CEACAM6.

Results: Functional analysis revealed that NEO-201 is capable of engaging enhancing NK-92 activity to kill tumor cells. Expression profiling revealed that various tumor cell lines expressed different levels of CEACAM5+ and NEO-201+ cells. Addition of NEO-201 significantly enhanced NK-92 cell cytotoxicity against highly CEACAM5+/NEO-201+ cells, suggesting that its activity is correlated with the level of CEACAM5+/NEO-201+ tumor cells. Furthermore, the % of NEO-201+ cells in the population of CD4+CD25highCD127negFoxP3+CD15s+CCR4+Tregs ranged from 60%-80%. NEO-201 mAb mediated CDC activity against Tregs.

Conclusions: This study demonstrates NEO-201 can block the interaction between tumor cell CEACAM5 and NK cell CEACAM1 to reverse CEACAM1-dependent inhibition of NK killing. NEO-201 can also target and eliminate human immunosuppressive regulatory T cells (Tregs).

Citation Format: Massimo Fantini, Maria Pia Morelli, Christina M. Annunziata, Philip M. Arlen, Kwong Y. Tsang. A therapeutic humanized anti-carcinoma monoclonal antibody (mAb) can enhance NK activity and target immunosuppressive regulatory T cells [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 4534.

Evaluation of the Anti-Tumor Activity of the Humanized Monoclonal Antibody NEO-201 in Preclinical Models of Ovarian Cancer

Purpose: Despite high initial response rates with cytoreductive surgery, conventional chemotherapy and the incorporation of biologic agents, ovarian cancer patients often relapse and die from their disease. New approaches are needed to improve patient outcomes. This study was designed to evaluate the antitumor activity of NEO-201 monoclonal antibody (mAb) in preclinical models of ovarian cancer where the NEO-201 target is highly expressed.

Experimental Design: Functional analysis of NEO-201 against tumor cell lines was performed by antibody-dependent cellular cytotoxicity (ADCC) assays. Binding of NEO-201 to tumor tissues and cell lines were determined by immunohistochemistry (IHC) and flow cytometry, respectively. Further characterization of the antigen recognized by NEO-201 was performed by mass spectrometry. Ovarian cancer models were used to evaluate the anti-tumor activity of NEO-201 in vivo. NEO-201 at a concentration of 250 g/mouse was injected intraperitoneally (IP) on days 1, 4, and 8. Human PBMCs were injected IP simultaneously as effector cells.

Results: Both IHC and flow cytometry revealed that NEO-201 binds prominently to the colon, pancreatic, and mucinous ovarian cancer tissues and cell lines. Immunoprecipitation of the antigen recognized by NEO-201 was performed in human ovarian, colon, and pancreatic cancer cell lines. From these screening, carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) and CEACAM6 were identified as the most likely targets of NEO-201. Our results confirmed that NEO-201 binds different types of cancers; the binding is highly selective for the tumor cells without cross reactivity with the surrounding healthy tissue. Functional analysis revealed that NEO-201 mediates ADCC killing against human ovarian and colorectal carcinoma cell lines in vitro. In addition, NEO-201 inhibited tumor growth in the presence of activated human PBMCs in orthotopic mouse models of both primary and metastatic ovarian cancer. Importantly, NEO-201 prolonged survival of tumor-bearing mice.

Conclusions: These data suggested that NEO-201 has an antitumor activity against tumor cells expressing its antigen. Targeting an antigen expressed in tumors, but not in normal tissues, allows patient selection for optimal treatment. These findings strongly indicate that NEO-201 warrants clinical testing as both a novel therapeutic and diagnostic agent for treatment of ovarian carcinomas. A first in human clinical trial evaluating NEO-201 in adults with chemo-resistant solid tumors is ongoing at the NIH clinical Center.

Evaluating biomarkers in metastatic castration-resistant prostate cancer patients treated with enzalutamide: PSA, circulating tumor cell counts, AR-V7 status and radiographic progression

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Background: Enzalutamideis ahighly effective treatment in metastatic castration resistant prostate cancer (mCRPC). Although Prostate Cancer Working Group (PCWG) guidelines recommend continuing treatment until radiographic/clinical progression (rPD/cPD), many patients discontinue therapy for rising PSA alone. Methods: We conducted an open label, randomized phase 2 trial in mCRPC patients untreated with docetaxel, abiraterone, or enzalutamide, comparing enzalutamide alone or in combination with PROSTVAC, a therapeutic cancer vaccine designed to induce an anti-tumor immune response. The study discontinued accrual after planned interim analysis indicated no difference in progression between the two arms. Patients were followed beyond 1st of 3 confirmed PSA rises until rPD. 49 patients were analyzed for Circulating Tumor Cell (CTC) count and AR-V7 status at 1st PSA rise and at rPD/cPD or last follow up. Results: 57 patients were enrolled with median follow up time of 55.4 mo. 49/57 (86%) patients had rising PSA; median time to 1st PSA rise for all patients was 6.4 mo (95% CI: 3.7-11.0 mo) after starting enzalutamide. 38/57 (67%) patients had progressive disease (majority with rPD; 1/38 (3%) with cPD); median time to progression for all patients was 23.3 mo (95% CI: 16.1-27.8 mo). 5 patients tested positive for AR-V7 within 30 days of rPD. In patients who experienced rPD/cPD, CTCs were detected in 11/24 (46%) samples taken at rPD vs. in only 3/24 (13%) samples taken at rising PSA. CTC counts were higher at rPD compared to samples taken at rising PSA (P = 0.004, Wilcoxon unpaired test). Of the 7 patients still being treated (median time on drug = 4.2 yrs), 2 experienced rising PSA; however none of the patients had detectable CTCs at a median of 30 days from last follow up. Conclusions: These data suggest that a rising PSA may not be a warning of near-term clinically significant disease progression in mCRPC patients treated with enzalutamide, given the 17-month difference between the first rise in PSA and ultimate rPD/cPD seen in this analysis. Further, CTCs and AR-V7 status associate strongly with rPD but not with rising PSA, adding biological rationale to the hypothesis that CTC counts and AR-V7 status are associated with disease progression. Collectively, these data highlight the need to continue to educate patients and providers on PCWG criteria for progression and appropriately-timed utilization of both therapies and diagnostic tests to maximize drug efficacy in mCRPC. Clinical trial information: NCT01867333 .

Correlation of clinical activity of NEO201 mAb with the expression of NK activation markers and levels of soluble factors

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Background: NEO-201 is a humanized IgG1 mAb that targets tumor-associated variants of CEACAM-5/6. NEO201 exerts anti-tumor activity by (NK)-mediated ADCC, CDC, and by enhancing NK cell cytotoxicity through blockade of CEACAM5-CEACAM1 interaction. The first in human phase I clinical trial is ongoing. Neutropenia caused DLT and was observed at 2mg/kg (DL 2). At DL2, 2/6 patients with colorectal cancers had stable disease. In the present study we evaluated the correlation between response, NK status, and profiles of soluble factors. Methods: This is a classic 3+3 dose escalation. NEO-201 is administered intravenously every 2 weeks, with 4 dose levels planned (DL1 = 1mg/kg, DL2 = 2mg/kg, DL3 = 4mg/kg and DL4 = 6mg/kg). So far, 3 patients received DL1 and 6 patients DL2. Safety is evaluated according to CTCAEv5.0, and response according to RECISTv1.1. Biological samples are collected at baseline, at 4, 24 and 72 hours after the first dose, and before C1D15 dose to understand NEO-201 pharmacokinetics (PK), effects on immune profile and correlation with treatment toxicity and response. CD56+/CD16+ NK cells were evaluated for modulation of NKG2D, CD107a, NKp46 (activation markers), and CEACAM1 (inhibitory marker) by flow cytometry. Soluble factors (cytokines, sMICA and sCEACAM5) were evaluated by ELISA. Results: Among the 3 patients achieving radiological SD, one (DL1) had clinical progression (PD) without radiological progression after 2 cycles due to mucous producing disease, a second patient (DL2) went off study after 2 cycles for drug unrelated issues, and the third patient (DL2) has stable disease (SD) for 6 months without significant toxicity. All other patients had radiologic PD after 2 cycles. Interestingly, baseline CD56+/CD16+ NK cells from the two patients with SD showed an increase in NKG2D, CD107a and NKp46, and a low expression of CEACAM1. They also had low serum levels of sMICA, sCEACAM5 and IL-6. On contrary, CD56+/CD16+ NK cells from patients with PD had low expression of NKG2D and CD107a, high expression of CEACAM1, and high levels of sMICA. Conclusions: High expression of activating markers and low expression of CEACAM1 on CD56+/CD16+ NK cells, as well as low levels of sMICA and sCEACAM5 correlate with clinical response to NEO-201. Thus, the activity of NK cells may serve as predictors for efficacy of tumor-targeting antibody therapy. Further correlation of these biomarkers with PK and CEACAM1/5/6 expression in patients’ tissue samples will provide further support for optimizing the use of NEO201. Clinical trial information: NCT03476681 .

Phase II Study of Ensituximab, a Novel Chimeric Monoclonal Antibody, in Adults with Unresectable, Metastatic Colorectal Cancer

PURPOSE

Patients with metastatic colorectal cancer refractory to chemotherapy have limited treatment options. Ensituximab (NEO-102) is a novel chimeric mAb targeting a variant of MUC5AC with specificity to colorectal cancer.

PATIENTS AND METHODS

Single-arm, phase II trial assessed the efficacy and safety of ensituximab in patients with advanced, refractory cancer who expressed MUC5AC antigen in tumor tissue. Ensituximab was administered intravenously every 2 weeks with 3 mg/kg as recommended phase II dose (RP2D). A minimum sample size of 43 patients was required on the basis of the assumption that ensituximab would improve median overall survival (OS) by 7 months using a one-sided significance level of 10% and 80% power. Written informed consent was obtained from all patients.

RESULTS

Sixty-three patients with advanced, refractory colorectal cancer were enrolled and 53 subjects were treated in phase II arm. Median age was 58 years and 46% of the patients were female. Among 57 evaluable patients, median OS was 6.8 months. No responses were observed, and stable disease was achieved in 21% of the patients. The most common treatment-related adverse events (AE) at RP2D included fatigue (38%), anemia (30%), nausea (15%), vomiting (11%), increased bilirubin (9%), constipation (8%), decreased appetite (6%), and diarrhea (6%). Serious AEs at least possibly related to ensituximab occurred in 4 patients and included anemia, nausea, increased bilirubin, and hypoxia. No patients discontinued treatment due to drug-related AEs.

CONCLUSIONS

Ensituximab was well tolerated and demonstrated modest antitumor activity in patients with heavily pretreated refractory colorectal cancer.

PSA progression compared to radiographic or clinical progression in metastatic castration-resistant prostate cancer patients treated with enzalutamide

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Background: Enzalutamideis ahighly effective treatment in patients with metastatic castration resistant prostate cancer (mCRPC). Although Prostate Cancer Working Group Guidelines (PCWG) recommend continuing treatment until radiographic progression of disease (rPD) or clinical progression (cPD), many patients discontinue therapy for rising PSA alone. Methods: We conducted an open label, randomized phase 2 clinical trial in mCRPC patients (on testosterone suppression therapy) previously untreated with docetaxel, abiraterone, or enzalutamide, comparing enzalutamide alone or in combination with PROSTVAC, a therapeutic cancer vaccine designed to induce an anti-tumor immune response. The study discontinued accrual after a planned interim analysis indicated no difference in progression between the two arms. Patients were followed beyond PSA progression (first of three confirmed PSA rises, evaluated monthly) until rPD per PCWG (scans done every 3 months per protocol). Results: A total of 57 patients were enrolled with a median follow up time of 55.4 months. Of those, 47 (82%) patients were Caucasian and seven (12%) patients were African American. The median age of patients on enrollment was 67.2 years. 49/57 (86%) patients had PSA progression and the median time to first PSA rise for all 57 patients combined was 6.4 months (95% CI: 3.7-11.0 months) after starting enzalutamide. 38/57 (67%) patients experienced progressive disease (majority with rPD and 1/38 (3%) with cPD), with the median time to progression for all 57 patients of 23.3 months (95% CI: 16.1-27.8 months). Conclusions: Consistent with PCWG recommendations, these data suggest that a rising PSA may not be a warning of near-term clinically significant disease progression in mCRPC patients given the nearly 17-month difference between the first rise in PSA and ultimate rPD or cPD seen in this analysis. These data highlight the need to continue to educate patients and providers on PCWG criteria for progression, which were also used in original trials that led to the FDA approval of enzalutamide, so as not to substantially limit the potential efficacy of mCRPC therapies such as enzalutamide. Clinical trial information: NCT01867333.

Indirect mechanisms of action of a novel IgG1 monoclonal antibody, NEO-201, to enhance immune killing of tumor

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Background: NEO-201 is an IgG1 mAb targeting variants of CEACAM5/6 that demonstrates tumor sensitivity and specificity. Functional analysis revealed that NEO-201 is capable of engaging innate immune effector mechanism including ADCC and CDC to directly kill tumor cells expressing its target. Previous studies demonstrated safety/tolerability in non-human primates, and an on going clinical trial at the NCI is currently exploring its dosing and safety. We have explored indirect mechanisms of its action that may enhance immune tumor killing. NEO-201 has the ability to enhance NK activity by blocking the binding of CEACAM5 on tumor cells to CEACAM1 on NK cells. In addition NEO-201 can target and eliminate regulatory T cells (Tregs). Methods: In vitro functional assays, using various human tumor cell lines as target cells and NK-92 cells (CEACAM1+/CD16−) as effectors, were conducted to assess the ability of NEO-201to enhance antitumor cytotoxicity of NK-92 cells by blocking the interaction between CEACAM5 on tumor cells and CEACAM1 on NK cells. In addition, flow cytometry analsyis and CDC assays were performed to evaluate the ability of NEO-201 to target and eliminate human Tregs in vitro. Results: Addition of NEO-201 significantly enhanced NK-92 cell cytotoxicity against highly CEACAM5+/NEO-201+ cells, suggesting that its activity is correlated with the level of CEACAM5+/NEO-201+ tumor cells. Furthermore, NEO-201 targets human Tregs and mediates killing of opsonized T-reg cells via CDC. Conclusions: Previously we have demonstrated the ability of NEO-201 as an IgG1 mab to destroy tumor cells expressing its target directly through both ADCC and CDC. This study suggests that in addition, NEO-201may also mediate immune killing through additional mechanisms including blocking the interaction between CEACAM5 on tumor cells and CEACAM1 on NK cells to reverse CEACAM1-dependent inhibition of NK cytotoxicity. In addition, we have shown that NEO-201 is also able to recognize and eliminate human Tregs. Ongoing studies are looking at leveraging this phenomenon by combining NEO-201 with checkpoint inhibitors.

Phase I with expansion cohorts in a study of NEO-201 in adults with chemo-resistant solid tumors

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Background: NEO-201 is a humanized IgG1 monoclonal antibody (mAb) generated against tumor-associated antigens (TAA) from colorectal cancer. Our preclinical data demonstrated that NEO-201 exerts anti-tumor activity by NK-mediated ADCC and CDC against several tumor types. We identified NEO-201 antigen as a tumor-associated form of CEACAM-5 and -6, which is expressed by tumor tissue but is not present in the surrounding healthy tissue. Methods: This is a first-in-human phase 1 study to determine the maximum tolerated dose (MTD) and recommended phase II dose (RP2D) of NEO-201 in adults with advanced solid tumors that have high likelihood of expression NEO201 antigen and have progressed to standard of treatments. This is a classic 3+3 dose escalation, with cohort expansion at the MTD. NEO-201 is administered intravenously every two weeks, and at four dose levels (DL1 = 1mg/kg, DL2 = 2mg/kg, DL3 = 4mg/kg and DL4 = 6mg/kg). Patients are evaluated for safety according to CTCAEv5.0., and for response according to RECISTv1.1. Biological samples are collected to understand NEO-201 pharmacokinetics, the effects on immune profile and the correlation with treatment toxicity and response. Results: Here we report the safety data and pharmacokinetics from DL1 and 2. A total of 9 evaluable patients were enrolled. Prolonged neutropenia, defined as ³G2 neutropenia lasting for >7 days, was observed at DL2. The cohort was expanded to a total of 6 patients and no further DLTs were observed. Seven out of nine of the patients enrolled had colon cancer, two had pancreatic cancer and one had hormone positive breast cancer. The most frequent treatment-related AEs were infusion reaction which was observed in all patients, and moderate fatigue (33%). Best response was SD observed in two patients (one on each of DL1 and DL2). Dose escalation continues on DL3 and DL4. NEO201 antigen expression in patient tumor tissue, circulating CEACAM6/CEACAM5, and MICA will be evaluated to correlate with response and toxicity. Conclusions: NEO201 has shown some promising activity. PK and PD studies are ongoing to better understand dosing schedule, toxicity profile and to identify biomarkers for patient selection. Clinical trial information: NCT03476681.

Clinical efficacy of abiraterone and enzalutamide metastatic castration sensitive prostate cancer patients who progressed rapidly on docetaxel with a genomic analysis

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Background: Docetaxel has become a standard of care for mCSPC. Enzalutamide and abiraterone have been proven to improve survival in metastatic castration-resistant prostate cancer (mCRPC) patients. Little is known about patients who have been treated with docetaxel for mCSPC and subsequent therapeutic responses. This retrospective analysis is to evaluate the response duration of abiraterone and enzalutamide in patients who previously received docetaxel for mCSPC but developed mCRPC within 12 months. Methods: Clinical Trial NCT02649855 enrolled patients with newly diagnosed mCSPC who were treated with standard androgen deprivation therapy (ADT) and docetaxel (75 mg/m2 every 3 weeks for 6 cycles) sequenced with immunotherapy (PROSTVAC) from February 2016 to present. Patients who had progression (based on consecutive PSA rises or imaging) within 1 year of completing docetaxel and went on to subsequent abiraterone/enzalutamide were evaluated. (Note these are different PSA progression criteria than used in CHAARTED, Sweeney, NEJM, 2015). A PCR-based NGS panel (OncoMine Comprehensive Assay v3) will evaluate available tissue from these patients. Results: Of the 46 patients evaluated regardless of immunotherapy sequence, 15 (33%) went on subsequent therapy after progression on docetaxel for mCSPC, with 12 patients starting abiraterone/enzalutamide (7 with high volume disease and 5 with low volume disease). The median age was 62 (41-83) years. 6/12 patients (50%) initiated enzalutamide and 6/12 patients (50%) initiated abiraterone. The median duration of treatment for both was 7.43 (1.53 – 16.0) months, the median time to prostate-specific antigen (PSA) progression was 2 (0 – 11) months; the median duration of PSA decline was 2 months in patients with both high and low volume disease. Of note, 3/12 (25%) of patients did not have PSA response, all of them had high volume disease. Conclusions: These data from a small cohort suggest that patients who have progression within 12 months of completing docetaxel for mCSPC have limited subsequent benefit from enzalutamide or abiraterone. Additional studies are required to determine optimal timing and treatment sequence for patients with mCSPC who rapidly develop mCRPC. Clinical trial information: NCT02649855.

Phase 1 with expansion cohorts in a study of NEO-201 in adults with chemo-resistant solid tumors

TPS2645

Background: NEO-201 is a novel humanized IgG1 monoclonal antibody (mAb) generated against the Hollinshead allogenic colorectal cancer vaccine platform. Briefly, tumor-associated antigens (TAA) derived from tumor membrane fractions pooled from colorectal cancer surgical specimens were screened for delayed-type hypersensitivity and evaluated in clinical trials. The original vaccine was used to generate monoclonal antibodies, one of which is NEO-201. In preclinical data generated in our laboratory, we have demonstrated that NEO-201 exert anti-tumor activity by natural killer (NK)-mediated antibody-dependent cytotoxicity (ADCC) against several tumor type including colorectal and pancreatic cancer models (Fantini, et al. 2018). We have identified NEO-201 antigen as a glycosylated form of CEACAM-5 and -6, which is expressed by tumor tissue but is not present in the surrounding healthy tissue (David, et al. 2018). This could result in a specific anti-tumor activity without significant normal tissue toxicity. Nevertheless, toxicity was further assessed in non-human primates and transient neutropenia was the only adverse event observed. Based on this data we designed a first in human phase I trial to evaluate the safety, maximum-tolerated dose (MTD), pharmacokinetics (PK) and pharmacodynamics (PD) of the humanized monoclonal antibody NEO-201. Methods: This is a first-in-human phase 1 study with expansion cohort to determine the maximum tolerated dose (MTD) and recommended phase II dose (RP2D) of NEO-201 in adults with advanced solid tumors that have high likelihood pof expression NEO201 antigen and have progressed to standard of treatments and have a PS0-2 ECOG. Study design is a classic Fibonacci (3+3) dose escalation, with a cohort expansion at the MTD. NEO-201 is administered intravenously every two weeks, and four different dose levels will be explored (DL1 = 1mg/kg, DL2 = 2mg/kg, DL3 = 4mg/kg and DL4 = 6mg/kg). No intra-patient dose escalation is allowed. Patients will be evaluated for safety every two weeks, with weekly laboratory testing, according to CTCAEv4.0. and with a DLT window of 28 days (cycle 1). Response will be assessed every 8 weeks (2 cycles of treatment) according to RECISTv1.1. Additionally, biological samples will be collected to understand NEO-201 pharmacokinetic, the effect on the immune process and their correlation with treatment toxicity and response. As of February 2019 we have completed enrollment in the first DL and are evaluating for DLT. Clinical trial information: NCT03476681.

A phase I and randomized phase II study of cabozantinib plus docetaxel and prednisone (C+DP) versus docetaxel and prednisone (DP) alone in metastatic castrate-resistant prostate cancer (mCRPC)

173

Background: A phase I study of Cabozantinib (C) in combination with docetaxel (D) and prednisone (P) in patients (pts) with mCRPC determined that 40 mg daily was the maximum tolerated dose of C in combination with D and P (C+DP). We report a pooled analysis of the phase I and randomized phase II study comparing C+DP to DP alone. Methods: Eligible pts had mCRPC without prior chemotherapy in the castrate setting. All pts received a fixed dose of D (75 mg/m2IV day one of each 21 day cycle) and P (5 mg PO twice daily), and in the C+DP group, C at three escalating dose levels: 20 mg, 40 mg, or 60 mg in the phase I cohort (all PO daily) and 40 mg daily in the phase II cohort. Results: A total of 32 pts received C+DP (19 pts in phase I and 13 pts in the phase II cohort). 12 pts received DP alone. Baseline characteristics for C+DP vs DP included median age 69 (45 – 84) vs 69 (50-83) and median PSA 74.8 ng/ml (0.01-4093.7) vs 309.5 ng/ml (94.6 – 2649) respectively. Clinical trial information: NCT01683994. 18/32 C+DP pts had previous enzalutamide or abiraterone, with a median PFS of 13.6 months (95% CI: 5.2 – 21.0). 23/32 pts (72%) treated with C+DP required dose reduction or discontinuation of C, and 10/32 (31%) required C discontinuation. 2/32 patients (6%) in the C+DP group died on protocol, possibly related to study drug (sudden death NOS/venous thromboembolism). Grade 4 adverse events (AEs) in the C+DP group included: neutropenia (28%), leukopenia (6%), pulmonary embolism (3%), and mucositis (3%) and in DP: hyperglycemia (8%). Grade 3 AEs (>10%) in C+DP included: neutropenia (31%), febrile neutropenia (16%), leukopenia (13%), hypophosphatemia (13%) and in DP: anemia (17%). Conclusions: In pts with mCRPC, C+DP is associated with a greater PFS and PSA responses compared to DP alone. Toxicities with the combination were manageable. Further study is required to better define the potential benefits of C+DP in mCRPC.[Table: see text]

Efficacy of abiraterone and enzalutamide in patients who had disease progression within twelve months of completing docetaxel for metastatic castration sensitive prostate cancer

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Background: Docetaxel is a standard of care for mCSPC. Enzalutamide and abiraterone have been proven to improve survival in metastatic castration-resistant prostate cancer (mCRPC) patients. Little is known about patients who have been treated with docetaxel for mCSPC and subsequent therapeutic responses. This retrospective analysis is to evaluate the response duration of abiraterone and enzalutamide in patients who previously received docetaxel for mCSPC but developed mCRPC within 12 months. Methods: Clinical Trial NCT02649855 enrolled patients with newly diagnosed mCSPC who were treated with standard androgen deprivation therapy (ADT) and docetaxel (75 mg/m2 every 3 weeks for 6 cycles) sequenced with immunotherapy (PROSTVAC) from February 2016 to present. Patients who had progression (based on consecutive PSA rises or imaging) within 1 year of completing docetaxel and went on to subsequent abiraterone/enzalutamide were evaluated. (Note these are different PSA progression criteria than used in CHAARTED, Sweeney, NEJM, 2015). Results: Of the 46 patients evaluated regardless of immunotherapy sequence, 15 (33%) went on subsequent therapy after progression on docetaxel for mCSPC, with 12 patients starting abiraterone/enzalutamide (6 each with high and low volume disease). The median age was 62 (41-83) years. 7/12 patients (58.3%) initiated enzalutamide and 5/12 patients (41.7%) initiated abiraterone. The median duration of treatment for both was 7.12 (1.53–16.0) months, the median time to prostate-specific antigen (PSA) progression was 5.54 (0–15.83) months; 5/12 (41.7%) of patients did not have PSA response. Of note, patients with low volume disease had a median treatment duration of 5.88 months, 3 of them did not have PSA response. Conclusions: These data from a small cohort suggest that patients who have progression within 12 months of completing docetaxel for mCSPC have limited subsequent benefit from enzalutamide or abiraterone. Additional studies are required to determine optimal timing and treatment sequence for patients with mCSPC who rapidly develop mCRPC. Clinical trial information: NCT02649855.

An IL-15 Superagonist, ALT-803, Enhances Antibody-Dependent Cell-Mediated Cytotoxicity Elicited by the Monoclonal Antibody NEO-201 Against Human Carcinoma Cells

BACKGROUND

A major mechanism of action for therapeutic antibodies is antibody-dependent cell-mediated cytotoxicity (ADCC). ALT-803 is an interleukin-15 superagonist complex that enhances ADCC against human carcinoma cells in vitro and exerts an antitumor activity in murine, rat, and human carcinomas in vivo. The authors investigated the ability of ALT-803 to modulate ADCC mediated by the humanized IgG1 monoclonal antibody (mAb) NEO-201 against human carcinoma cells.

MATERIALS AND METHODS

ALT-803 modulating activity on ADCC mediated by NEO-201 was evaluated on several NEO-201 ligand-expressing human carcinoma cells. Purified human natural killer (NK) cells from multiple healthy donors were treated with ALT-803 before their use as effectors in ADCC assay. Modulation of NK cell phenotype and cytotoxic function by exposure to ALT-803 was evaluated by flow cytometry and gene expression analysis.

RESULTS

ALT-803 significantly enhanced ADCC mediated by NEO-201. ALT-803 also upregulated NK activating receptors, antiapoptotic factors, and factors involved in the NK cytotoxicity, as well as downregulated gene expression of NK inhibiting receptors.

CONCLUSIONS

These findings indicate that ALT-803 can enhance ADCC activity mediated by NEO-201, by modulating NK activation and cytotoxicity, suggesting a possible clinical use of ALT-803 in combination with NEO-201 for the treatment of human carcinomas.

Immunotherapy for biochemically recurrent prostate cancer

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Background: Annually about 30-50,000 men are diagnosed with biochemically recurrent prostate cancer (BCRpc), defined by a rising PSA after radical prostatectomy (RP) or definitive radiation therapy (RT) with negative conventional imaging (CT and bone scan). Standard treatments include salvage therapies, androgen deprivation or surveillance. The role of immunotherapy in BCRpc is undefined. Methods: This study evaluates PROSTVAC, a pox-viral based therapeutic cancer vaccine targeting PSA, in BCRpc. Key eligibility criteria include PSA > 0.8 after RP or > 2.0 after RT with a maximum PSA of 30, PSA doubling time (DT): 5-15 months; testosterone > 100, negative CT and bone scan. Patients (pts) are randomized to vaccine for 6 months or 6 months surveillance followed by 6 months of vaccine. In a post hoc analysis delayed PSA declines were characterized as a confirmed PSA decline after an intra-study apex PSA (ISAP) defined by a peak PSA affirmed by a contiguous PSA within 10% (to exclude lab variations). 80 pts will be enrolled at NCI, Dana-Farber Cancer Institute and Memorial Sloan Kettering Cancer Center. Results: Of the 26 pts enrolled thus far, 22 have been followed for > 9 months after vaccine and are evaluable. On-study median values were age 66.8 years (54-78), PSA 2.67 ng/ml (0.83-28.5), PSA DT 7.5 months (5.1-14.9). 8 pts (38%) had delayed PSA declines after ISAP (-12% to -99%). Of 13 pts on surveillance for 6 months, only one pt had a similar decline lasting only 56 days. Conclusions: Preliminary data from this study suggests that PROSTVAC may be associated with delayed, but sustained PSA declines in BCRpc which are rarely seen in surveillance alone. Additional data will be acquired from this study, but this provides rationale to develop immunotherapy combinations in BCRpc. Clinical trial information: NCT02649439. [Table: see text]

Preclinical Characterization of a Novel Monoclonal Antibody NEO-201 for the Treatment of Human Carcinomas

NEO-201 is a novel humanized IgG1 monoclonal antibody that was derived from an immunogenic preparation of tumor-associated antigens from pooled allogeneic colon tumor tissue extracts. It was found to react against a variety of cultured human carcinoma cell lines and was highly reactive against the majority of tumor tissues from many different carcinomas, including colon, pancreatic, stomach, lung, and breast cancers. NEO-201 also exhibited tumor specificity, as the majority of normal tissues were not recognized by this antibody. Functional assays revealed that treatment with NEO-201 is capable of mediating both antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) against tumor cells. Furthermore, the growth of human pancreatic xenograft tumors in vivo was largely attenuated by treatment with NEO-201 both alone and in combination with human peripheral blood mononuclear cells as an effector cell source for ADCC. In vivo biodistribution studies in human tumor xenograft-bearing mice revealed that NEO-201 preferentially accumulates in the tumor but not organ tissue. Finally, a single-dose toxicity study in non-human primates demonstrated safety and tolerability of NEO-201, as a transient decrease in circulating neutrophils was the only related adverse effect observed. These findings indicate that NEO-201 warrants clinical testing as both a novel diagnostic and therapeutic agent for the treatment of a broad variety of carcinomas.

Abstract 3025: Preclinical characterization of a novel monoclonal antibody targeting a neo-antigen expressed in ovarian and GI malignancies

Objectives: We have developed a novel humanized IgG1 monocolonal antibody, NEO-201, which targets a neoantigen expressed on ovarian and GI malignancies. This antigen has homology to CEACAM; however, it has specificity to tumor tissues and not normal tissues. Our aims were as follows: (1) to evaluate the expression of this antigen on tumor cell lines derived from various ovarian and GI cancers; and (2) to determine the functionality of NEO-201.

Methods: Expression of the antigen was identified by western blot analysis and flow cytometry. Functionality was determined by an antibody dependent cell-mediated cytotoxicity (ADCC) assay using the antigen-expressing cell lines identified by western blot analysis. Cell lines not expressing the antigen were used as negative controls. The effector cells used in the ADCC assay were natural killer (NK) cells isolated from PBMCs of normal donors and high-affinity activated NK (haNK) cells. haNK cells are NK-92 cells genetically engineered to express the high-affinity variant of human CD16 (FcgRIIIA-V158) and the human IL-2 gene. haNK cells have little or no inhibitory expression of killer cell immunoglobulin-like receptors, a unique feature that may optimize their highly cytotoxic activity against a broad range of malignancies.

Results: Using western blot analysis, 2 of 5 ovarian cancer cell lines (OV90 and PE01) and 1 of 2 colorectal cancer cell lines (LS174T) stained positively for NEO-201. Flow cytometry analysis on ovarian, colorectal, and pancreatic cancer cell lines confirmed the expression of the NEO-201 neoantigen on 1 of 2 ovarian cancer cell lines (OV90), 1 of 2 colorectal cancer cell lines (LS174T), and 2 of 2 pancreatic cancer cell lines (ASPC-1 and CFPAC-1). ADCC assay was performed using OV90 and ASPC-1 tumor cell lines. Cell lines not expressing the neoantigen were used as negative controls. Killing of tumor cells expressing the neoantigen was also observed with NEO-201 alone; however, the lysis was significantly augmented when NK cells from the PBMCs of normal donors or haNK cells were included in the ADCC assay.

Conclusions: These finding demonstrate that the NEO-201 neoantigen is expressed on several tumor cell lines representing ovarian and GI malignancies. NEO-201 can mediate ADCC activity in the presence of NK cells and NK cell lines. In addition, NEO-201 can induce apoptosis in tumor cell lines expressing the NEO-201 neoantigen. Furthermore, preliminary studies demonstrated that this neoantigen is expressed in numerous cancer types (not shown). In vivo studies as well as IND-related studies are planned.

Citation Format: Kristen Zeligs, Philip M. Arlen, Kwong Tsang, Lidia Hernandez, Massimo Fantini, Christina M. Annunziata. Preclinical characterization of a novel monoclonal antibody targeting a neo-antigen expressed in ovarian and GI malignancies [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 3025. doi:10.1158/1538-7445.AM2017-3025

Ensituximab (E) in patients (pts) with refractory metastatic colorectal cancer (mCRC): Results of a phase I/II clinical trial

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Background: E is an investigational, novel, chimeric monoclonal IgG1 antibody derived from an immunogenic neoantigen with sequence homology to MUC5AC that is preferentially expressed with exquisite specificity to pancreatic cancer and CRC. Its mechanism of action is via antibody-dependent cellular cytotoxicity (ADCC). The efficacy and safety of E was evaluated in a single-arm, open-label, phase 1/2 clinical trial of adult pts with refractory mCRC. Methods: Pts were selected based on > 20% expression of tumor antigen, as measured by immunohistochemistry. Based on phase 1 results, E was administered 3 mg/kg IV every 2 weeks until unacceptable toxicity or disease progression. Primary endpoint was overall survival (OS). Serum cytokine levels were analyzed at baseline, day 4, and day 15. E-mediated ADCC of CD16 genotype V/V, V/F, and F/F pt PBMCs was measured with an IN-111 release assay using the E target-expressing ASPC-1 pancreatic cancer cell line. Results: Fifty-seven and 63 pts were evaluable for OS and safety, respectively. Median OS was significantly longer than historical control: 6.8 vs 5.0 months (mo); p = 0.007; 95% CI: 5.39,8.02. Three pts were alive at end of study (21, 21, and 24 mo); 21 pts survived ≥ 12 mo. Pts had a median of 4 prior therapies (range 2-9); 25% had received regorafenib. Forty-seven pts were evaluable by RECIST, and 20 (43%) had stable disease of target lesions at end of first course (day 57). E was well tolerated, with < 2% grade 3 and no grade 4 toxicities. There were no trends in serum cytokine and chemokine levels. Analysis of 56 samples (8 V/V, 26 V/F, 17 F/F, and 5 undetermined) showed that V/V PBMCs had significantly higher E-mediated ADCC than PBMCs harboring other genotypes. No correlation between CD16 polymorphism and pt outcome was observed. Conclusions: E demonstrated excellent tolerability and encouraging OS in this heavily pretreated population. Correlative in vitro data suggest that E can mediate higher levels of ADCC activity in individuals with a V/V versus other genotypes. The lack of correlation between CD16 polymorphism and pt outcomes in this study suggests that other immune-related factors (under investigation) may impact the efficacy of E in vivo. Clinical trial information: NCT01040000.

Phase II trial of docetaxel, bevacizumab, lenalidomide and prednisone in patients with metastatic castration-resistant prostate cancer

OBJECTIVE

To determine the safety and clinical efficacy of two anti-angiogenic agents, bevacizumab and lenalidomide, with docetaxel and prednisone.

PATIENTS AND METHODS

Eligible patients with metastatic castration-resistant prostate cancer enrolled in this open-label, phase II study of lenalidomide with bevacizumab (15 mg/kg), docetaxel (75 mg/m(2) ) and prednisone (10 mg daily). Docetaxel and bevacizumab were administered on day 1 of a 3-week treatment cycle. To establish safety, lenalidomide dosing in this combination was escalated in a conventional 3 + 3 design (15, 20 and 25 mg daily for 2 weeks followed by 1 week off). Patients received supportive measures including prophylactic pegfilgrastim and enoxaparin. The primary endpoints were safety and clinical efficacy.

RESULTS

A total of 63 patients enrolled in this trial. Toxicities were manageable with most common adverse events (AEs) being haematological, and were ascertained by weekly blood counts. Twenty-nine patients (46%) had grade 4 neutropenia, 20 (32%) had grade 3 anaemia and seven (11%) had grade 3 thrombocytopenia. Despite frequent neutropenia, serious infections were rare. Other common non-haematological grade 3 AEs included fatigue (10%) and diarrhoea (10%). Grade 2 AEs in >10% of patients included anorexia, weight loss, constipation, osteonecrosis of the jaw, rash and dyspnoea. Of 61 evaluable patients, 57 (93%), 55 (90%) and 33 (54%) had PSA declines of >30, >50 and >90%, respectively. Of the 29 evaluable patients, 24 (86%) had a confirmed radiographic partial response. The median times to progression and overall survival were 18.2 and 24.6 months, respectively.

CONCLUSIONS

With appropriate supportive measures, combination angiogenesis inhibition can be safely administered and potentially provide clinical benefit. These hypothesis-generating data would require randomized trials to confirm the findings.

TARP vaccination is associated with slowing in PSA velocity and decreasing tumor growth rates in patients with Stage D0 prostate cancer

T-cell receptor alternate reading frame protein (TARP) is a 58-residue protein over-expressed in prostate and breast cancer. We investigated TARP peptide vaccination's impact on the rise in PSA (expressed as Slope Log(PSA) or PSA Doubling Time (PSADT)), validated tumor growth measures, and tumor growth rate in men with Stage D0 prostate cancer. HLA-A*0201 positive men were randomized to receive epitope-enhanced (29-37-9V) and wild-type (27-35) TARP peptides administered as a Montanide/GM-CSF peptide emulsion or as an autologous peptide-pulsed dendritic cell vaccine every 3 weeks for a total of five vaccinations with an optional 6th dose of vaccine at 36 weeks based on immune response or PSADT criteria with a booster dose of vaccine for all patients at 48 and 96 weeks. 41 patients enrolled with median on-study duration of 75 weeks at the time of this analysis. Seventy-two percent of patients reaching 24 weeks and 74% reaching 48 weeks had a decreased Slope Log(PSA) compared to their pre-vaccination baseline (p = 0.0012 and p = 0.0004 for comparison of overall changes in Slope Log(PSA), respectively). TARP vaccination also resulted in a 50% decrease in median tumor growth rate (g): pre-vaccine g = 0.0042/day, post-vaccine g = 0.0021/day (p = 0.003). 80% of subjects exhibited new vaccine-induced TARP-specific IFNγ ELISPOT responses but they did not correlate with decreases in Slope Log(PSA). Thus, vaccination with TARP peptides resulted in significant slowing in PSA velocity and reduction in tumor growth rate in a majority of patients with PSA biochemical recurrence.

Docetaxel Alone or in Combination With a Therapeutic Cancer Vaccine (PANVAC) in Patients With Metastatic Breast Cancer: A Randomized Clinical Trial

IMPORTANCE

Previous phase 1 and 2 trials of PANVAC, a poxviral-based cancer vaccine, have suggested clinical efficacy in some patients with breast, ovarian, and colorectal cancer and have shown evidence of immunologic activity. Preclinical data have shown that docetaxel can modify tumor phenotype, making tumor cells more amenable to T cell-mediated killing.

OBJECTIVE

The goal of this study was to determine if the treatment combination of docetaxel and PANVAC improves clinical outcomes in patients with metastatic breast cancer compared with docetaxel treatment alone.

DESIGN, SETTING, AND PARTICIPANTS

Between May 2006 and February 2012, this open-label, phase 2 randomized clinical trial enrolled 48 patients with metastatic breast cancer of all subtypes, without limitation on other lines of previous therapy, to receive treatment with either docetaxel with PANVAC (arm A) or docetaxel alone (arm B). Final clinical data were collected on September 16, 2013. All patients were treated at either the National Cancer Institute or the Department of Breast Medical Oncology, MD Anderson Cancer Center.

MAIN OUTCOMES AND MEASURES

The primary end point was progression-free survival (PFS), using a phase 2.5 statistical design, with the intent of identifying a trend toward benefit (defined as 1-sided P≤.10) to guide a larger trial design. Secondary end points included safety and immunologic correlative studies.

RESULTS

Forty-eight participants were enrolled: 25 were randomized to the combination treatment arm A, and 23 to arm B. No patient remained in the study at the time of the final analysis. Patient and tumor characteristics were well matched. Analysis of adverse events in both treatment arms demonstrated very little difference between the 2 groups. In the combination treatment arm (arm A), statistically significant increases were noted in the frequency of grades 1 and 2 edema (P=.02, likely related to greater median number of docetaxel cycles) and injection-site reactions (P<.001). In the final data analysis, median PFS was 7.9 months in arm A vs 3.9 months in arm B (hazard ratio, 0.65 [95% CI, 0.34-1.14]; P=.09).

CONCLUSIONS AND RELEVANCE

The results suggest that the combination of PANVAC with docetaxel in metastatic breast cancer may provide a clinical benefit. This study was hypothesis generating and provides both rationale and statistical assumptions for a larger definitive randomized study.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00179309.

A phase II therapeutic, open label, multi-center clinical trial of NPC-1C, a chimeric monoclonal antibody(mAb), in adults with chemotherapy refractory metastatic colorectal cancer (mCRC), initial results

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Background: NEO-102 is a novel chimeric mAb targeting a variant of MUC5AC with specificity to colorectal cancer. Its mechanism of action is through antibody dependent cellular cytotoxicity (ADCC). An earlier, phase I study, established the maximum tolerated dose at 3.0 mg/kg IV every 2 weeks with encouraging early signs of clinical activity. We report initial results of the subsequent phase II study. Methods: This is a single arm, open label multi-center clinical trial of NEO-102 in adults with mCRC pts who failed at least two lines of standard chemotherapy (C). An immunohistochemistry (IHC) based companion diagnostic assay was used to select eligible pts whose tumors express the target in > 20% of tumor cells. NEO-102 at 3.0 mg/kg IV was administered q 2 weeks until disease progression. The primary endpoint was OS. A minimum of 43 pts were needed assuming that treatment with NEO-102 will improve OS by 40% (7.0 months) using a one-sided significance level of 10% and 80% power for this study compared to historical control of 5 months. Additional objectives were to evaluate response rate as measured by RECIST criteria and analyze patient PBMCs for ADCC and immune cytokine profiling. Results: A total of 47 pts enrolled were evaluable. 26 pts were male and 35 pts were white. Twenty-four out of 47 pts (51%) remain alive as of September 2015 with an ongoing median OS of 7.0 months (Range 2-22 months). Of these heavily pre-treated pts, 42 were evaluable for response, 13 (31%) demonstrated stable disease by RECIST. Seven pts had more than 4 doses of treatment, maximum 13 doses. Grade 3 adverse events were anemia 1/47 (2%), hyperbilirubinemia 1/47 (2%), diarrhea 1/47 (2%), fatigue 1/47 (2%), headache 1/47 (2%), nausea 1/47 (2%) and vomiting 1/47 (2%). No grade 4 toxicities were reported. Conclusions: In the monotherapy phase 2 study of NEO 102 in patients with refractory mCRC preliminary results demonstrate excellent tolerability and encouraging OS. Updated OS and Progression Free Survival data will be presented at the ASCO 2016 GI Cancers symposium. Additional combination trials with NEO-102 and C are underway. Clinical trial information: NCT01040000.

Comparison of survival of African-American (AA) patients (pts) in docetaxel (D)-based combination therapies in metastatic castrate-resistant prostate cancer (mCRPC)

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Background: AA pts experience greater prostate cancer (PC) incidence and mortality compared to Caucasian (C) pts but are underrepresented in clinical trials (CTs). Greater representation of AAs is required to explore differences in clinical benefit in advanced disease where recent data has reaffirmed the role of D. Methods: In a retrospective analysis, baseline characteristics, Gleason score (GS), ECOG PS, number of cycles (cys), maximum prostate-specific antigen (PSA) declines, radiographic responses, overall survival (OS) and progression-free survival (PFS) were captured in 2 recent D based CTs. Results: Of 136 pts, 28 (21%) self-identified as Black or AA. Median age of AA pts is 66 (50-78 yrs). Median GS is 8 (5-10). Median ECOG PS is 1 (0-2). 15 pts have bone and soft tissue disease; 13 pts have bone only disease. Median number of cys is 28.5 (1-63). Of 27 evaluable pts, 26 had PSA declines (-26 to -99%). Radiographic responses include 11 (39%) partial responses and 16 (57%) pts with stable disease. Median OS for AAs is 29.0 months (mos) (95% CI: 20.9-34.7 mos); median PFS is 21.5 mos (95% CI: 13.7-28.9 mos). Median OS for all non-AA pts is 24.8 mos (95% CI: 21.8-29.5 mos); median PFS is 16.1 mos (95% CI: 14.1-20.1 mos). The VEGF-634G > C SNP, associated with a more aggressive phenotype of PC, was evaluated in 54 pts. No evidence was found that genotype frequency varies between C and AA pts. Conclusions: In this analysis, AA pts did not have inferior OS (29 mos) or PFS (21.5 mos) outcomes compared to non-AA pts (24.8, 16.1 mos). Further analysis from larger studies is required to determine differential benefits of D for AA pts compared to non-AA pts. Clinical trial information: NCT00089609, NCT00942578.

Phase I Trial of a Yeast-Based Therapeutic Cancer Vaccine (GI-6301) Targeting the Transcription Factor Brachyury

The nuclear transcription factor brachyury has previously been shown to be a strong mediator of the epithelial-to-mesenchymal transition (EMT) in human carcinoma cells and a strong negative prognostic factor in several tumor types. Brachyury is overexpressed in a range of human carcinomas as well as in chordoma, a rare tumor for which there is no standard systemic therapy. Preclinical studies have shown that a recombinant Saccharomyces cerevisiae (yeast) vaccine encoding brachyury (GI-6301) can activate human T cells in vitro. A phase I dose-escalation (3+3 design) trial enrolled 34 patients at 4 dose levels [3, 3, 16, and 11 patients, respectively, at 4, 16, 40, and 80 yeast units (YU)]. Expansion cohorts were enrolled at 40- and 80-YU dose levels for analysis of immune response and clinical activity. We observed brachyury-specific T-cell immune responses in the majority of evaluable patients despite most having been heavily pretreated. No evidence of autoimmunity or other serious adverse events was observed. Two chordoma patients showed evidence of disease control (one mixed response and one partial response). A patient with colorectal carcinoma, who enrolled on study with a large progressing pelvic mass and rising carcinoembryonic antigen (CEA), remains on study for greater than 1 year with stable disease, evidence of decreased tumor density, and decreased serum CEA. This is the first-in-human study to demonstrate the safety and immunogenicity of this therapeutic cancer vaccine and provides the rationale for exploration in phase II studies. A randomized phase II chordoma study is now enrolling patients.

Cabozantinib (C) plus docetaxel (D) and prednisone (P) in metastatic castrate-resistant prostate cancer (mCRPC)

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Background: Docetaxel (D) improves overall survival in metastatic castrate-resistant prostate cancer (mCRPC), but benefits remain short-lived. Clinical data suggests patients (pts) with mCRPC treated with anti-androgen therapy like abiraterone (AA) or enzalutamide (ENZA) have decreased responses to subsequent therapy due to cross-resistance in the androgen pathway targeted by D, AA, or ENZA(van Soest et al, Eur J Cancer 49:18, 2013). Combining D with other agents, like cabozantinib (C), could target different cellular signaling pathways potentially minimizing tumor resistance. Methods: D naive pts receive 75 mg/m2 IV on day 1 of a 21 day cycle, and prednisone (P) 5 mg po q12 hours with C at 3 dose levels: 20, 40, or 60 mg po daily until maximum tolerated dose (MTD) is defined. In phase 2, pts who have progressed on AA or ENZA, enroll on a randomized 2 arm cohort comparing D plus C to D alone. Results: 20 pts have been accrued; 4 at 20 mg C, 8 at 40 mg C, and 7 at 60 mg C. On phase 2, 1 pt is randomized to D alone. Median age is 68 (44-84 yrs). Median baseline PSA is 94.7 (0.01-754.1 ng/mL). Gleason score is 9 (7-10). Median cycles is 9.5 (1-33). 8 pts have bone only disease, 12 pts have bone and soft tissue disease. Common grade 2 and grade 3 adverse events possibly related to C: hand/foot syndrome (4/16), oral mucositis (4/16), hypophosphatemia (4/16), and fatigue (3/16). The MTD of C is 40 mg daily with D. 15 pts were previously treated with AA or ENZA. In 13 patients previously treated with AA, median PFS has not been reached, with a median potential follow up of 12.4 months. Six month PFS is 77.8% and 9 month PFS is 60.5%. Conclusions: D plus P may have limited benefits after disease progression on AA as seen in 3 retrospective analyses demonstrating a median PFS survival of 4.6 months or less (Mezynski J, et al. Ann Oncol 23;11, 2012) (Aggarwal R, et al. Clin Genitourin Cancer 12;5, 2014) (Schweizer MT, et al. Eur Urol 66;4, 2014). PFS results seen in this trial compare favorably to previously published data of treatment with D after AA in mCRPC, suggesting the addition of C to D may help overcome acquired resistance. Further randomized trials will determine if C in combination with D will enhance clinical outcomes. Clinical trial information: NCT01683994.

A multicenter randomized phase II study of NPC-1C (N) in combination with gemcitabine (G) and nab-paclitaxel (A) versus G and A alone in patients with metastatic or locally advanced pancreatic cancer (PC) previously treated with folfirinox (F)

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Background: PC carries a poor prognosis. F has improved overall survival (OS) compared to G leading to its use as a 1st line treatment for patients (pts) with advanced PC. Similarly, the combination of G and A has demonstrated OS benefit. No data exists for G/A in the 2nd line setting. Many oncologists continue to sequence F treatment followed upon disease progression by G/A for pts with advanced PC with good performance status. N is a chimeric monoclonal IgG1 antibody recognizing an aberrantly glycosylated MUC5AC specific to GI tumors. Its mechanism of action is through ADCC. An IHC based companion diagnostic assay is utilized to select pts whose tumors express the target (approx. 65-70%). A prior study administering N to pts with advanced PC refractory to chemotherapy was well tolerated with disease stabilization and prolongation of OS. Furthermore 2 of 5 pts receiving the combination of G+N following progression on F remain alive at 10 and 12 months respectively. Methods: The primary objective of this phase 2.5 study is to determine if the combination of N and G plus A can improve the OS for pts who have PC over G plus A alone in the post F setting. The trial is a 2-arm randomized 1:1 multi-institution trial of N plus G and A vs. G and A. Eligible pts would be expected to have an estimated 4.5 to 4.8 month median OS with G alone, but this may be enhanced somewhat with the addition of A. The goal is to determine if the use of N along with G and A will result in pts having an increased median OS of 8 months vs. an estimated 5 months without N. Kaplan-Meier curves and a two-tailed log-rank test will be the primary analysis methods. All pts must have tissue positive for the MUC5AC variant (≥20% by IHC). Because N has been established to be safe when given with G alone but not with the combination of G and A, stopping rules for safety will be adhered to for the first 6 pts randomized to G/A plus N. Enrollment to the study has commenced. Correlative studies will utilize both PBMCs and serum for immune monitoring. Frequency, phenotype and function of different immune cells (including CD8+ T cells, CD4+ T cells, Tregs and MDSCs) will be analyzed. Clinical trial information: NCT01834235.

A phase I/II multicenter study of the chimeric monoclonal antibody NEO102 (NPC-1C) in adults with refractory pancreatic (PC) and colorectal cancer (CC)

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Background: NPC-1C (NEO102) is a novel chimeric monoclonal antibody that recognizes a variant form of MUC5AC expressed specifically by human pancreatic (P) and colorectal (CC) tumors. The mechanism of action is through Antibody-dependent cell-mediated cytotoxicity (ADCC). We are presenting results of dose escalation and preplanned expansion cohort of NEO-102. Methods: This is a Phase Ib/IIa, open label, multicenter clinical trial and expansion cohort of NEO102. Patients are preselected based on an Immunuhistochemistry (IHC) companion diagnostic assay. Antigen expression cut off was set at 20% expression. NEO102 was administered every 2 weeks IV with tumor assessments every 8 weeks. The primary objective was to determine safety and tolerability of NEO102. Secondary objectives include overall survival, clinical benefit, pharmacokinetics and explore the immunologic correlates. Results: Twenty-six patients (3 pancreatic and 23 colon cancer) are evaluable for toxicity and response. Median age is 55 (32 - 68) years, 14 are male. Two dose limiting toxicities were experienced at 4.0 mg/kg: grade 3 hyperbilirubinemia (n=4) and grade 3 anemia (n=1). The maximum tolerated dose (MTD) and recommended phase-2 dose (RP2D) was established at 3.0 mg/kg. Of 12 patients evaluated for response, 5 demonstrated stable disease by RECIST (42%; 4 CC, 1 P) after the first course (Day 57) and 1 PC had SD after the second course (Day 114). OS is 4.5+ months (1+ - 13.5+), median duration of treatment of 74+ days (36-133). Of those screened, 60-70% tumors were IHC positive. Immune correlates (including cytokine profile, HAMA) will be presented. Conclusions: Treatment with NEO102 is well tolerated with a manageable safety profile. RP2D is 3.0 mg/kg. Preliminary results with NEO102 have demonstrated signs of clinical activity based on stabilization of disease in heavily pretreated patients with PC and CC. A Phase II study of NEO102 monotherapy in pancreatic and colon cancer is now enrolling patients. In addition, a combination study using NEO102 with cytotoxic chemotherapy in metastatic pancreatic cancer is underway. Clinical trial information: NCT01040000.

Phase I clinical trial of oral 2-methoxyestradiol, an antiangiogenic and apoptotic agent, in patients with solid tumors

PURPOSE

To determine the maximum-tolerated dose (MTD) and toxicity profile of the novel anticancer agent, 2-methoxyestradiol (2ME2) administered orally, in patients with solid tumors.

MATERIALS AND METHODS

Twenty patients with refractory solid tumors were enrolled. 2ME2 was given orally starting at 400 mg bid with dose escalation until 3000 mg bid. Tumor biopsies were taken before and after starting the drug to assess for microvessel density by CD 31 and cell proliferation by Ki67 immunohistochemistry. Serial plasma samples collected up to 50 hours after first single oral dose for characterization of pharmacokinetics, were analyzed using liquid chromatography tandem mass-spectrometry.

RESULTS

Eleven men and nine women received 2ME2 at dose levels of 400 mg bid (n = 3), 800 mg bid (n = 3), 1600 mg bid (n = 6), 2200 mg bid (n = 5) and 3000 mg bid (n = 3). There were no dose limiting toxicities, therefore the MTD was not defined. There was one episode of grade 4 angioedema in the 1600 mg bid dose level 38 days into 2ME2 treatment. Other toxicities were mild to moderate. A patient with clear cell carcinoma of the ovary had a partial response at 1600 mg bid dose level lasting over three years.

CONCLUSION

MTD for 2ME2 was not reached at dose of 3000 mg bid. The trial was closed due to extremely low plasma concentrations of 2ME2 relative to the doses administered. 2ME2 treatment had no effect on microvessel density (CD31 immunostaining) and cell proliferation (Ki-67 immunostaining). A new formulation of 2ME2 with improved bioavailability is currently being developed.

Abstract CT415: A Phase I/IIA multicenter clinical trial of the chimeric monoclonal antibody NEO102 (NPC-1C) in adults with refractory pancreatic and colorectal cancer

Background:NPC-1C, (NEO-101 and NEO102, Precision Biologics, Inc) is a novel chimeric monoclonal antibody being developed as a treatment for pancreatic and colorectal cancers. NPC-1C recognizes a variant form of MUC5AC expressed specifically by human pancreatic and colorectal tumors. A Phase I trial of NEO-101 has been completed and reported previously. This Phase IIA study utilizes NEO-102, a glycoengineered form of NEO-101 with improved stability and decreased red cell agglutination.

Methods: This is a Phase Ib/IIa, open label, multicenter dose escalation clinical trial with Neo-102 for patients with refractory pancreatic and colorectal cancer. The primary objective is to determine safety, tolerability of escalating doses of NEO-102. Secondary objectives are to assess pharmacokinetics as well as immune response at each dose level, evaluate clinical benefit as measured by RECIST criteria and overall survival, and to explore the immunologic correlates associated with NEO-102. Analyses of patient peripheral blood mononuclear cells (PBMCs) for antibody-dependent cell-mediated cytotoxicity (ADCC) and immune cytokine profiling utilizing the Milliplex MAP Human Cytokine/Chemokine Panel are planned to assess for immunologic outcome, and for correlation with clinical benefit. Patients with histologically confirmed adenocarcinoma of the pancreas who have progressed after front line chemotherapy; or metastatic colorectal cancer who have progressed after at least 2 chemotherapy regimens; whose tumors express the target NEO-102 antigen as defined as ≥ 20% positive stain by NPC-1C immunohistochemistry (IHC) are eligible. Patients have good performance status (KPS ≥ 50%) and adequate hematologic, hepatic and renal function are eligible. Major exclusion criteria include uncontrolled brain metastases, ascites, or other uncontrolled medical illness. Dose escalation was performed in a standard 3+3 design at doses of 1.5mg/kg, 2 mg/kg, 3 mg/kg and 4 mg/kg.

Results: A total of 12 patients (2 pancreatic and 10 colon cancer) have been enrolled. Preplanned dose escalation to the 4 mg/kg dose has been completed and no dose limiting toxicity was observed. Median age is 58 years, 7 are male, median number of prior treatment regimens are 4+ (range 1+ to 8+) Treatment related AEs include grade 1 and 2 diarrhea, fatigue, mucositis, nausea, pruritus, epigastric pain, nasal congestion, insomnia, mouth ulcers, back pain, congestion, weight loss, chills facial flushing and fever, and grade 3 diarrhea and anemia. No severe adverse events (SAE) have been deemed to be drug related. Overall response rate includes 4 patients with PD and 5 patients have achieved SD and 3 patients are too early to evaluate. Median duration of treatment is 56+ days (Range 29 to131+). Conclusions: We have completed dose escalation with NEO-102, a first in man monoclonal antibody with a unique mechanism of action. Treatment is well tolerated with manageable safety profile. Due to encouraging preliminary clinical activity, as demonstrated by disease stabilization in a heavily pretreated population, a Phase II study of NEO-102 monotherapy in pancreatic and colon cancer is now enrolling patients. In addition, a combination study using NEO102 with cytotoxic chemotherapy in metastatic pancreatic cancer is underway.

Citation Format: Muhammad Shaalan Beg, Michael Morse, Sandip P. Patel, Sharon Mavroukakis, Melony Beatson, Philip M. Arlen, Nilofer S. Azad. A Phase I/IIA multicenter clinical trial of the chimeric monoclonal antibody NEO102 (NPC-1C) in adults with refractory pancreatic and colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT415. doi:10.1158/1538-7445.AM2014-CT415