Pharmacology: Mechanism of Action: Sacituzumab govitecan is a Trop-2-directed antibody-drug conjugate. Sacituzumab is a humanized antibody that recognizes Trop-2. The small molecule, SN-38, is a topoisomerase I inhibitor, which is covalently attached to the antibody by a linker. Pharmacology data suggest that sacituzumab govitecan binds to Trop-2-expressing cancer cells and is internalized with the subsequent release of SN-38 via hydrolysis of the linker. SN-38 interacts with topoisomerase I and prevents re-ligation of topoisomerase I-induced single strand breaks. The resulting DNA damage leads to apoptosis and cell death. Sacituzumab govitecan decreased tumor growth in mouse xenograft models of triple-negative breast cancer.
Pharmacodynamics: The TRODELVY exposure-response relationships and pharmacodynamic time course for efficacy have not been fully characterized.
Cardiac electrophysiology: The maximum mean change from baseline was 9.7 msec (the upper bound of the two-sided 90% confidence interval is 16.8 msec) at the recommended dose. A positive exposure-response relationship was observed between QTc increases and SN-38 concentrations.
Clinical Studies: Locally Advanced or Metastatic Triple-Negative Breast Cancer: ASCENT: Efficacy was evaluated in a multicenter, open-label, randomized study (ASCENT; NCT02574455) conducted in 529 patients with unresectable locally advanced or metastatic triple-negative breast cancer (mTNBC) who had relapsed after at least two prior chemotherapies for breast cancer (one of which could be in the neoadjuvant or adjuvant setting provided progression occurred within a 12 month period). All patients received previous taxane treatment in either the adjuvant, neoadjuvant, or advanced stage unless there was a contraindication or intolerance to taxanes during or at the end of the first taxane cycle. Magnetic resonance imaging (MRI) to determine brain metastases was required prior to enrollment for patients with known or suspected brain metastases. Patients with brain metastases were allowed to enroll up to a pre-defined maximum of 15% of patients in the ASCENT study. Patients with known Gilbert's disease or bone-only disease were excluded.
Patients were randomized (1:1) to receive TRODELVY 10 mg/kg as an intravenous infusion on Days 1 and 8 of a 21-day (n=267) or physician's choice of single agent chemotherapy (n=262). Single agent chemotherapy was determined by the investigator before randomization from one of the following choices: eribulin (n=139), capecitabine (n=33), gemcitabine (n=38), or vinorelbine (n=52).
Patients were treated until disease progression or unacceptable toxicity. The major efficacy outcome was progression-free survival (PFS) in patients without brain metastases at baseline (i.e., BMNeg) as measured by a blinded, independent, centralized review assessed using Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 criteria. Additional efficacy measures included PFS for the full population (all patients with and without brain metastases) and overall survival (OS).
The median age of patients in the full population (n=529) was 54 years (range: 27 to 82 years); 99.6% were female; 79% were White, 12% were Black/African American; and 81% of patients were <65 years of age. All patients had an ECOG performance status of 0 (43%) or 1 (57%). Forty-two percent of patients had hepatic metastases, 9% were BRCA1/BRCA2 mutational status positive, and 70% were TNBC at diagnosis. Twelve percent had baseline brain metastases previously treated and stable (n=61; 32 on TRODELVY arm and 29 on single agent chemotherapy arm). Overall, 29% of patients had received prior PD-1/PD-L1 therapy. Thirteen percent of patients in the TRODELVY group in the full population received only 1 prior line of systemic therapy in the metastatic setting.
The efficacy results are summarized in Table 1 and are shown in Figure 1 and Figure 2. Efficacy results for the subgroup of patients who had received only 1 prior line of systemic therapy in the metastatic setting (in addition to having disease recurrence or progression within 12 months of neoadjuvant/adjuvant systemic therapy) were consistent with those who had received at least two prior lines in the metastatic setting. (See Table 1, Figures 1 and 2.)
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An exploratory analysis of PFS in patients with previously treated, stable brain metastases showed a stratified HR of 0.65 (95% CI: 0.35, 1.22). The median PFS in the TRODELVY arm was 2.8 months (95% CI: 1.5, 3.9) and the median PFS with single agent chemotherapy was 1.6 months (95% CI: 1.3, 2.9). Exploratory OS analysis in the same population showed a stratified HR of 0.87 (95% CI: 0.47, 1.63). The median OS in the TRODELVY arm was 6.8 months (95% CI: 4.7, 14.1) and the median OS with single agent chemotherapy was 7.4 months (95% CI: 4.7, 11.1).
IMMU-132-01: The efficacy of TRODELVY was evaluated in a multicenter, single-arm, study (NCT01631552) that enrolled 108 patients with metastatic triple-negative breast cancer (mTNBC) who had received at least two prior
anticancer therapies for metastatic disease. Patients with bulky disease, defined as a mass >7 cm, were not eligible. Patients with treated brain metastases not receiving high dose steroids (>20 mg prednisone or equivalent) for at least four weeks were eligible. Patients with known Gilbert's disease were excluded.
Patients received TRODELVY 10 mg/kg intravenously on Days 1 and 8 of a 21-day treatment cycle. Patients were treated with TRODELVY until disease progression or intolerance to the therapy. Tumor imaging was obtained every 8 weeks, with confirmatory CT/MRI scans obtained 4-6 weeks after an initial partial or complete response, until progression requiring treatment discontinuation. Major efficacy outcome measures were investigator assessed overall response rate (ORR) using RECIST 1.1 and duration of response.
The median age was 55 years (range: 31 to 80 years); 87% of patients were younger than 65 years. The majority of patients were female (99%) and White (76%). At study entry, all patients had an ECOG performance status of 0 (29%) or 1 (71%). Seventy-six percent had visceral disease, 42% had hepatic metastases, 56% had lung/pleura metastases, and 2% had brain metastases. Twelve patients (11%) had Stage IV disease at the time of initial diagnosis.
The median number of prior systemic therapies received in the metastatic setting was 3 (range: 2-10). Prior chemotherapies in the metastatic setting included carboplatin or cisplatin (69%), gemcitabine (55%), paclitaxel or docetaxel (53%), capecitabine (51%), eribulin (45%), doxorubicin (24%), vinorelbine (16%), cyclophosphamide (19%), and ixabepilone (8%).
Overall, 98% of patients had received prior taxanes and 86% had received prior anthracyclines either in the (neo)adjuvant or metastatic setting.
Table 2 summarizes the efficacy results. (See Table 2.)
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Locally Advanced or Metastatic HR-Positive, HER2-Negative Breast Cancer: TROPiCS-02 Study: The efficacy of TRODELVY was evaluated in a multicenter, open label, randomized study (TROPiCS-02; NCT03901339) conducted in 543 patients with unresectable locally advanced or metastatic HR-positive, HER2-negative (IHC 0, IHC 1+ or IHC 2+/ISH-) breast cancer whose disease has progressed after the following in any setting: a CDK 4/6 inhibitor, endocrine therapy, and a taxane; patients received at least two prior chemotherapies in the metastatic setting (one of which could be in the neoadjuvant or adjuvant setting if recurrence occurred within 12 months).
Patients were randomized (1:1) to receive TRODELVY 10 mg/kg as an intravenous infusion on Days 1 and 8 of a 21 day cycle (n=272) or single agent chemotherapy (n=271). Single agent chemotherapy was determined by the investigator before randomization from one of the following choices: eribulin (n=130), vinorelbine (n=63), gemcitabine (n=56), or capecitabine (n=22). Randomization was stratified by the following factors: prior chemotherapy regimens for metastatic disease (2 vs. 3-4), visceral metastasis (Yes or No), and endocrine therapy in the metastatic setting for at least 6 months (Yes or No).
Patients were treated until disease progression or unacceptable toxicity. Administration of TRODELVY was permitted beyond RECIST-defined disease progression if the patient was clinically stable and considered by the investigator to be deriving clinical benefit. The primary efficacy outcome measure was PFS as determined by BICR per RECIST v1.1. Additional efficacy measures included OS, ORR by BICR, and DOR by BICR.
The median age of patients in the study population was 56 years (range: 27-86 years), 26% of patients were 65 years or over. The majority of patients were female (99%); 67% were White, 4% were Black and 3% were Asian, and 26% were of unknown race. Patients received a median of 7 (range: 3 to 17) prior systemic regimens in any setting and 3 (range: 0 to 8) prior systemic chemotherapy regimens in the metastatic setting. Approximately 42% of patients had 2 prior chemotherapy regimens for treatment of metastatic disease compared to 58% of patients who had 3 to 4 prior chemotherapy regimens and all patients had an ECOG performance status of 0 (45%) or 1 (55%). Ninety-five percent of patients had visceral metastases. Most patients received endocrine therapy in the metastatic setting for ≥6 months (86%).
TRODELVY demonstrated a statistically significant improvement in PFS and OS versus single agent chemotheraphy.
The efficacy results are summarized in Table 3 and Figure 3 and Figure 4. (See Table 3, Figures 3 and 4.)
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Pharmacokinetics: The serum pharmacokinetics of sacituzumab govitecan and SN-38 were evaluated in patients
with mBC who received sacituzumab govitecan as a single agent at a dose of 10 mg/kg. The pharmacokinetic parameters of sacituzumab govitecan and free SN-38 are presented in Table 4. (See Table 4.)
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Distribution: Based on population pharmacokinetic analysis, the
steady state volume of distribution of sacituzumab govetican is
3.6 L.
Elimination: The median elimination half-life (t½) of sacituzumab govitecan and free SN-38 in patients with metastatic triple negative breast cancer was 23.4 and 17.6 hours, respectively. Based on population pharmacokinetic analysis,
the estimated mean (%CV) clearance of the sacituzumab govitecan is
0.13 L/h (12%).
Metabolism: No metabolism studies with sacituzumab govitecan have been conducted. SN-38 (the small molecule moiety of sacituzumab govitecan) is metabolized via UGT1A1. The glucuronide metabolite of SN-38 (SN-38G) was detectable in the serum of patients.
Specific Populations: Pharmacokinetic analyses in patients treated with TRODELVY did not identify an effect of age (27 to 88 years), race (White, Black, or Asian), or mild renal impairment to moderate renal impairment (CLcr 30 to 89 mL/min) on the pharmacokinetics of sacituzumab govitecan. Renal elimination is known to contribute minimally to the excretion of SN-38, the small molecule moiety of sacituzumab govitecan. There are no data on the pharmacokinetics of sacituzumab govitecan in patients with
severe renal impairment (CLcr 15 to 29 mL/min), or end-stage renal disease (CLcr
<15 mL/min).
Patients with Hepatic Impairment: The exposure of sacituzumab govitecan is similar in patients with mild hepatic impairment (total bilirubin ≤ULN with AST > ULN, or bilirubin >1.0 to
≤1.5 ULN with any AST;
n=257) to patients with normal hepatic function (total bilirubin or AST
<ULN;
n=526).
Sacituzumab govitecan
and free SN-38 exposures are unknown in patients with moderate (total bilirubin >1.5 to 3.0 × ULN) or severe (total bilirubin >3.0 × ULN) hepatic impairment.
Drug Interaction Studies: No drug-drug interaction studies were conducted with sacituzumab govitecan or its components. Inhibitors or inducers of UGT1A1
may increase or decrease SN-38 exposure, respectively [see Interactions].
Pharmacogenomics: SN-38 is metabolized via UGT1A1 [see Pharmacokinetics as previously mentioned]. Genetic variants of the UGT1A1 gene such as the UGT1A1*28 allele lead to reduced UGT1A1 enzyme activity. Individuals who are homozygous
or heterozygous for the UGT1A1*28 allele are at increased risk for neutropenia, febrile neutropenia, and anemia from TRODELVY
compared to individuals who are wildtype (*1/*1) [see Increased Risk of Adverse Reactions in Patients with Reduced UGT1A1 Activity under Precautions]. Approximately 20% of the Black or African American population, 10% of the White population, and 2% of the East Asian population are homozygous for the UGT1A1*28 allele
(*28/*28).
Approximately 40% of the Black or African American population, 50% of the White population, and 25% of the East Asian population are heterozygous for the UGT1A1*28 allele (*1/*28). Decreased function alleles other than UGT1A1*28 may be present in certain populations.
Immunogenicity: The detection of antibody formation is highly dependent on the sensitivity and specificity of the assay. Differences in
assay methods preclude meaningful comparisons of the incidence of anti-drug antibodies in the studies described previously with the incidence of anti-drug antibodies in other studies, including those of TRODELVY.
During the median 4-month treatment period across clinical studies in patients treated with TRODELVY, 9 (1.1%) of 785
patients developed antibodies to sacituzumab govitecan; 6 of these patients (0.8% of all patients treated with
TRODELVY) had neutralizing antibodies against sacituzumab govitecan. Because of the low occurrence of anti-drug
antibodies, the effect of these antibodies on the pharmacokinetics, pharmacodynamics, safety, and/or effectiveness of
sacituzumab govitecan is unknown.
Toxicology: Nonclinical Toxicology: Carcinogenesis, Mutagenesis, Impairment of Fertility: Carcinogenicity studies have not been conducted with sacituzumab govitecan.
SN-38 was clastogenic in an
in vitro mammalian cell micronucleus test in Chinese hamster ovary cells and was not mutagenic in an
in vitro bacterial reverse mutation (Ames) assay.
Fertility studies with sacituzumab govitecan have not been conducted. In a repeat-dose toxicity study in cynomolgus monkeys, intravenous administration of sacituzumab govitecan on Day 1 and Day 4 resulted in endometrial atrophy, uterine hemorrhage, increased follicular atresia of the ovary, and atrophy of vaginal epithelial cells at doses ≥60 mg/kg (≥6 times the human recommended dose of 10 mg/kg based on body weight).