Sacituzumab Govitecan-hziy in Refractory Metastatic Triple-Negative Breast Cancer.

BACKGROUND: Standard chemotherapy is associated with low response rates and short progression-free survival among patients with pretreated metastatic triple-negative breast cancer. Sacituzumab govitecan-hziy is an antibody-drug conjugate that combines a humanized monoclonal antibody, which targets the human trophoblast cell-surface antigen 2 (Trop-2), with SN-38, which is conjugated to the antibody by a cleavable linker. Sacituzumab govitecan-hziy enables delivery of high concentrations of SN-38 to tumors. METHODS: We conducted a phase 1/2 single-group, multicenter trial involving patients with advanced epithelial cancers who received sacituzumab govitecan-hziy intravenously on days 1 and 8 of each 21-day cycle until disease progression or unacceptable toxic effects. A total of 108 patients received sacituzumab govitecan-hziy at a dose of 10 mg per kilogram of body weight after receiving at least two previous anticancer therapies for metastatic triple-negative breast cancer. The end points included safety; the objective response rate (according to Response Evaluation Criteria in Solid Tumors, version 1.1), which was assessed locally; the duration of response; the clinical benefit rate (defined as a complete or partial response or stable disease for at least 6 months); progression-free survival; and overall survival. Post hoc analyses determined the response rate and duration, which were assessed by blinded independent central review. RESULTS: The 108 patients with triple-negative breast cancer had received a median of 3 previous therapies (range, 2 to 10). Four deaths occurred during treatment; 3 patients (2.8%) discontinued treatment because of adverse events. Grade 3 or 4 adverse events (in ≥10% of the patients) included anemia and neutropenia; 10 patients (9.3%) had febrile neutropenia. The response rate (3 complete and 33 partial responses) was 33.3% (95% confidence interval [CI], 24.6 to 43.1), and the median duration of response was 7.7 months (95% CI, 4.9 to 10.8); as assessed by independent central review, these values were 34.3% and 9.1 months, respectively. The clinical benefit rate was 45.4%. Median progression-free survival was 5.5 months (95% CI, 4.1 to 6.3), and overall survival was 13.0 months (95% CI, 11.2 to 13.7). CONCLUSIONS: Sacituzumab govitecan-hziy was associated with durable objective responses in patients with heavily pretreated metastatic triple-negative breast cancer. Myelotoxic effects were the main adverse reactions. (Funded by Immunomedics; IMMU-132-01 ClinicalTrials.gov number, NCT01631552.).

Sacituzumab govitecan (IMMU-132), an anti-Trop-2-SN-38 antibody-drug conjugate for the treatment of diverse epithelial cancers: Safety and pharmacokinetics.

BACKGROUND: Sacituzumab govitecan (IMMU-132), an antitrophoblastic cell-surface antigen (anti-Trop-2) humanized antibody-SN-38 conjugate, had encouraging efficacy in the phase 1 clinical trial. This report further examines the pharmacokinetics and safety of multiple cycles of IMMU-132 at doses of 8 or 10 mg/kg in patients with diverse advanced epithelial cancers. METHODS: Patients who had multiple prior therapies received IMMU-132 on days 1 and 8 of 21-day treatment cycles. Trop-2 staining of archived tumor specimens, clearance of IMMU-132 and its constituents (ie, immunoglobulin G [IgG], SN-38 [a camptothecin, the active component of irinotecan], and glucuronidated SN-38 [SN-38G]), antibody responses, and uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) levels were determined. Safety was assessed according to Common Terminology Criteria for Adverse Events version 4.0, and responses were assessed using Response Evaluation Criteria in Solid Tumors, version 1.1. RESULTS: Patients with diverse metastatic cancers who received IMMU-132 at 8 mg/kg (n = 81) and 10 mg/kg (n = 97) were examined. Trop-2 was positive in 93% of the available specimens. IMMU-132 cleared with a half-life of approximately 11 to 14 hours, reflecting the release of SN-38 from the conjugate; IgG cleared more slowly (half-life, approximately 103-114 hours). Most SN-38 in the serum (>95%) was bound to IgG. SN-38G concentrations were lower than SN-38 concentrations. Dose-limiting neutropenia after the first cycle was not correlated with SN-38 in serum or with UGT1A1 genotype. No antibody responses were detected. Objective responses were observed in several indications, including metastatic triple-negative breast cancer, confirming that 10 mg/kg produced an encouraging overall response. CONCLUSIONS: Sacituzumab govitecan has a predictable pharmacokinetic profile and manageable toxicity at doses of 8 and 10 mg/kg. With objective responses and a good therapeutic index at 10 mg/kg, this dose was chosen for future development. Cancer 2017;123:3843-3854. © 2017 American Cancer Society.

Sacituzumab Govitecan (IMMU-132), an Anti-Trop-2/SN-38 Antibody-Drug Conjugate: Characterization and Efficacy in Pancreatic, Gastric, and Other Cancers.

Sacituzumab govitecan (IMMU-132) is an antibody-drug conjugate (ADC) made from a humanized anti-Trop-2 monoclonal antibody (hRS7) conjugated with the active metabolite of irinotecan, SN-38. In addition to its further characterization, as the clinical utility of IMMU-132 expands to an ever-widening range of Trop-2-expressing solid tumor types, its efficacy in new disease models needs to be explored in a nonclinical setting. Unlike most ADCs that use ultratoxic drugs and stable linkers, IMMU-132 uses a moderately toxic drug with a moderately stable carbonate bond between SN-38 and the linker. Flow cytometry and immunohistochemistry disclosed that Trop-2 is expressed in a wide range of tumor types, including gastric, pancreatic, triple-negative breast (TNBC), colonic, prostate, and lung. While cell-binding experiments reveal no significant differences between IMMU-132 and parental hRS7 antibody, surface plasmon resonance analysis using a Trop-2 CM5 chip shows a significant binding advantage for IMMU-132 over hRS7. The conjugate retained binding to the neonatal receptor, but it lost greater than 60% of the antibody-dependent cell-mediated cytotoxicity activity compared to that of hRS7. Exposure of tumor cells to either free SN-38 or IMMU-132 demonstrated the same signaling pathways, with pJNK1/2 and p21(WAF1/Cip1) upregulation followed by cleavage of caspases 9, 7, and 3, ultimately leading to poly-ADP-ribose polymerase cleavage and double-stranded DNA breaks. Pharmacokinetics of the intact ADC in mice reveals a mean residence time (MRT) of 15.4 h, while the carrier hRS7 antibody cleared at a similar rate as that of the unconjugated antibody (MRT ∼ 300 h). IMMU-132 treatment of mice bearing human gastric cancer xenografts (17.5 mg/kg; twice weekly × 4 weeks) resulted in significant antitumor effects compared to that of mice treated with a nonspecific control. Clinically relevant dosing schemes of IMMU-132 administered either every other week, weekly, or twice weekly in mice bearing human pancreatic or gastric cancer xenografts demonstrate similar, significant antitumor effects in both models. Current Phase I/II clinical trials ( ClinicalTrials.gov , NCT01631552) confirm anticancer activity of IMMU-132 in cancers expressing Trop-2, including gastric and pancreatic cancer patients.

Improving the therapeutic index in cancer therapy by using antibody-drug conjugates designed with a moderately cytotoxic drug.

The antibody-drug conjugate (ADC), IMMU-130, of the moderately cytotoxic topoisomerase I inhibitor, SN-38, and the CEACAM5-targeted humanized antibody (mAb), labetuzumab, was evaluated in model systems of human colon carcinoma and in phase I clinical trials of heavily pretreated patients with metastatic colorectal cancer. The conjugate, designed with a near-homogeneous drug substitution of 7-8 SN-38/mAb and with a linker that released 50% of the drug in ∼20 h, showed significant antitumor effects compared to a nontargeted ADC in human tumor xenografts, which could be augmented in combination with bevacizumab. The advantage of fractionated dosing was demonstrated, with potential implications for the clinical dosing schedule. Biodistribution comparing IMMU-130 with labetuzumab showed that the conjugate cleared somewhat faster from the blood, but this did not affect tumor uptake and retention. The use of an ultrastable linker in the conjugate design abrogated antitumor effects. A tolerability study in rabbits showed a high safety margin, with no-observed-adverse-effect level (NOAEL) corresponding to a cumulative human-equivalent protein dose of 40-60 mg/kg. The preclinical findings appear to be corroborated in two phase I clinical trials, with high tolerability and evidence of antitumor activity, including objective responses. The impact of the ADC design on the utility of IMMU-130, tailored to a poorly internalizing target, is discussed.

Anti-CD22 90Y-epratuzumab tetraxetan combined with anti-CD20 veltuzumab: a phase I study in patients with relapsed/refractory, aggressive non-Hodgkin lymphoma.

A lingering criticism of radioimmunotherapy in non-Hodgkin lymphoma is the use of cold anti-CD20 antibody along with the radiolabeled anti-CD20 antibody. We instead combined radioimmunotherapy with immunotherapy targeting different B-cell antigens. We evaluated the anti-CD22 (90)Y-epratuzumab tetraxetan with the anti-CD20 veltuzumab in patients with aggressive lymphoma in whom at least one prior standard treatment had failed, but who had not undergone stem cell transplantation. Eighteen patients (median age 73 years, median of 3 prior treatments) received 200 mg/m(2) veltuzumab once-weekly for 4 weeks, with (90)Y-epratuzumab tetraxetan at planned doses in weeks 3 and 4, and (111)In-epratuzumab tetraxetan in week 2 for imaging and dosimetry. Veltuzumab effectively lowered levels of B cells in the blood prior to the radioimmunotherapy doses. No significant immunogenicity or change in pharmacokinetics of either agent occurred in combination. (111)In imaging showed tumor targeting with acceptable radiation dosimetry to normal organs. For (90)Y-epratuzumab tetraxetan, transient myelosuppression was dose-limiting with 6 mCi/m(2) (222 MBq/m(2)) × 2 being the maximal tolerated dose. Of 17 assessable patients, nine (53%) had objective responses according to the 2007 revised treatment response criteria, including three (18%) complete responses (2 relapsing after 11 and 13 months, 1 continuing to be clinically disease-free at 19 months), and six (35%) partial responses (1 relapsing after 14 months, 5 at 3 - 7 months). Responses occurred in patients with different lymphoma histologies, treated at different (90)Y dose levels, and with a predicted risk of poor outcome, most importantly including five of the six patients treated with the maximal tolerated dose (2 of whom achieved durable complete responses). In conclusion, the combination of (90)Y-epratuzumab tetraxetan and veltuzumab was well-tolerated with encouraging therapeutic activity in this difficult-to-treat population.

Predictive patient-specific dosimetry and individualized dosing of pretargeted radioimmunotherapy in patients with advanced colorectal cancer.

PURPOSE: Pretargeted radioimmunotherapy (PRIT) with bispecific antibodies (bsMAb) and a radiolabeled peptide reduces the radiation dose to normal tissues. Here we report the accuracy of an (111)In-labeled pretherapy test dose for personalized dosing of (177)Lu-labeled IMP288 following pretargeting with the anti-CEA × anti-hapten bsMAb, TF2, in patients with metastatic colorectal cancer (CRC). METHODS: In 20 patients bone marrow absorbed doses (BMD) and doses to the kidneys were predicted based on blood samples and scintigrams acquired after (111)In-IMP288 injection for individualized dosing of PRIT with (177)Lu-IMP288. Different dose schedules were studied, varying the interval between the bsMAb and peptide administration (5 days vs. 1 day), increasing the bsMAb dose (75 mg vs. 150 mg), and lowering the peptide dose (100 µg vs. 25 µg). RESULTS: TF2 and (111)In/(177)Lu-IMP288 clearance was highly variable. A strong correlation was observed between peptide residence times and individual TF2 blood concentrations at the time of peptide injection (Spearman's ρ = 0.94, P < 0.0001). PRIT with 7.4 GBq (177)Lu-IMP288 resulted in low radiation doses to normal tissues (BMD <0.5 Gy, kidney dose <3 Gy). Predicted (177)Lu-IMP288 BMD were in good agreement with the actual measured doses (mean ± SD difference -0.0026 ± 0.028 mGy/MBq). Hematological toxicity was mild in most patients, with only two (10 %) having grade 3-4 thrombocytopenia. A correlation was found between platelet toxicity and BMD (Spearman's ρ = 0.58, P = 0.008). No nonhematological toxicity was observed. CONCLUSION: These results show that individual high activity doses in PRIT in patients with CEA-expressing CRC could be safely administered by predicting the radiation dose to red marrow and kidneys, based on dosimetric analysis of a test dose of TF2 and (111)In-IMP288.

Al(18) F labeling of peptides and proteins.

Radiolabeled receptor-binding peptides and proteins have emerged as an important class of radiopharmaceuticals that have changed radionuclide imaging in clinical practice. Many strategies have been developed to radiolabel these peptide and proteins with fluorine-18. The majority of these methods is time-consuming and suffer from low yields. A more straightforward approach was proposed a few years ago, based on the chelation of aluminum fluoride by (1,4,7-triazacyclononane-1,4,7-triacetic acid). This approach has been optimized with regard to labeling yield and specific activity. In addition, crystallography studies have led to the design of optimized chelators. Subsequently, the Al(18) F technology is finding widespread use in labeling peptides and proteins. Various hapten peptides for pre-targeting studies have been labeled with Al(18) F, as well as αv ß3 integrin-binding peptides have been studied, and also larger peptides, such as exendin-4 and affibody molecules and heat-labile proteins have been labeled with Al(18) F. Here, we summarize the development, optimization, and applications of the Al(18) F labeling technology.

Sacituzumab govitecan plus platinum-based chemotherapy mediates significant antitumor effects in triple-negative breast, urinary bladder, and small-cell lung carcinomas.

Sacituzumab govitecan (SG) is an antibody-drug conjugate composed of an anti-Trop-2-directed antibody conjugated with the topoisomerase I inhibitory drug, SN-38, via a proprietary hydrolysable linker. SG has received United States Food and Drug Administration (FDA) approval to treat metastatic triple-negative breast cancer (TNBC), unresectable locally advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer, and accelerated approval for metastatic urothelial cancer. We investigated the utility of combining SG with platinum-based chemotherapeutics in TNBC, urinary bladder carcinoma (UBC), and small-cell lung carcinoma (SCLC). SG plus carboplatin or cisplatin produced additive growth-inhibitory effects in vitro that trended towards synergy. Immunoblot analysis of cell lysates suggests perturbation of the cell-cycle and a shift towards pro-apoptotic signaling evidenced by an increased Bax to Bcl-2 ratio and down-regulation of two anti-apoptotic proteins, Mcl-1 and survivin. Significant antitumor effects were observed with SG plus carboplatin in mice bearing TNBC or SCLC tumors compared to all controls (P < 0.0062 and P < 0.0017, respectively) and with SG plus cisplatin in UBC and SCLC tumor-bearing animals (P < 0.0362 and P < 0.0001, respectively). These combinations were well tolerated by the animals. Combining SG with platinum-based chemotherapeutics demonstrates the benefit in these indications and warrants further clinical investigation.

Pretargeted immuno-PET and radioimmunotherapy of prostate cancer with an anti-TROP-2 x anti-HSG bispecific antibody.

PURPOSE: TF12 is a trivalent bispecific antibody that consists of two anti-TROP-2 Fab fragments and one anti-histamine-succinyl-glycine (HSG) Fab fragment. The TROP-2 antigen is found in many epithelial cancers, including prostate cancer (PC), and therefore this bispecific antibody could be suitable for pretargeting in this cancer. In this study, the characteristics and the potential for pretargeted radioimmunoimaging and radioimmunotherapy with TF12 and the radiolabeled di-HSG peptide IMP288 in mice with human PC were investigated. METHODS: The optimal TF12 protein dose, IMP288 peptide dose, and dose interval for PC targeting were assessed in nude mice with s.c. PC3 xenografts. Immuno-positron emission tomography (PET)/CT was performed using TF12/68Ga-IMP288 at optimized conditions. The potential of pretargeted radioimmunotherapy (PRIT) using the TF12 pretargeted ¹77Lu-IMP288 was determined. RESULTS: TF12 and ¹¹¹In-IMP288 showed high and fast accumulation in the tumor [20.4 ± 0.6%ID/g at 1 h post-injection (p.i.)] at optimized conditions, despite the internalizing properties of TF12. The potential for PRIT was shown by retention of 50% of the ¹¹¹In-IMP288 in the tumor at 48 h p.i. One cycle of treatment with TF12 and ¹77Lu-IMP288 showed significant improvement of survival compared to treatment with ¹77Lu-IMP288 alone (90 vs. 67 days, p<0.0001) with no renal or hematological toxicity. CONCLUSION: TROP-2-expressing PC can be pretargeted efficiently with TF12, with very rapid uptake of the radiolabeled hapten-peptide, IMP288, sensitive immuno-PET, and effective therapy.

New lyophilized kit for rapid radiofluorination of peptides.

Radiolabeling compounds with positron-emitting radionuclides often involves a time-consuming, customized process. Herein, we report a simple lyophilized kit formulation for labeling peptides with (18)F, based on the aluminum-fluoride procedure. The prototype kit contains IMP485, a NODA (1,4,7-triazacyclononane-1,4-diacetate)-MPAA (methyl phenylacetic acid)-di-HSG (histamine-succinyl-glycine) hapten-peptide, [NODA-MPAA-D-Lys(HSG)-D-Tyr-D-Lys(HSG)-NH(2)], used for pretargeting, but we also examined a similar kit formulation for a somatostatin-binding peptide [IMP466, NOTA-D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Throl] bearing a NOTA ligand to determine if the benefits of using a kit can be extended to other AlF-binding peptides. The NODA-MPAA ligand forms a single stable complex with (AlF)(2+) in high yields. In order to establish suitable conditions for a facile kit, the formulation was optimized for pH, peptide to Al(3+) ratio, bulking agent, radioprotectant, and the buffer. For optimal labeling, the kit was reconstituted with an aqueous solution of (18)F(-) and ethanol (1:1), heated at 100-110 °C for 15 min, and then simply and rapidly purified using one of two equally effective solid-phase extraction (SPE) methods. Al(18)F-IMP485 was isolated as a single isomer complex, in high yield (45-97%) and high specific activity (up to 223 GBq/µmol), within 20 min. The labeled product was stable in human serum at 37 °C for 4 h and in vivo, urine samples showed the intact product was eliminated. Tumor targeting of the Al(18)F-IMP485 in nude mice bearing human colon cancer xenografts pretargeted with an anti-CEACAM5 bispecific antibody showed very low uptake (0.06% ± 0.02 ID/g) in bone, further illustrating its stability. At 1 h, pretargeted animals had high Al(18)F-IMP485 tumor uptake (28.1% ± 4.5 ID/g), with ratios of 9 ± 4, 123 ± 38, 110 ± 43, and 120 ± 108 for kidney, liver, blood and bone, respectively. Tumor uptake remained high at 3 h postinjection, with increased tumor/nontumor ratios. The NOTA-somatostatin-binding peptide also was fluorinated with good yield and high specific activity in the same kit formulation. However, yields were somewhat lower than those achieved with IMP485 containing the NODA-MPAA ligand, likely reflecting this ligand's superior binding properties over the simple NOTA. These studies indicate that (18)F-labeled peptides can be reproducibly prepared as stable Al-F complexes with good radiochemical yield and high specific activity using a simple, one-step, lyophilized kit followed by a rapid purification by SPE that provides the (18)F-peptide ready for patient injection within 30 min.