Antibody-drug conjugates (ADCs) targeting TROP-2 in lung cancer

ABSTRACT

Introduction

The advent of antibody-drug conjugates (ADCs) represents a renewed strategy in the era of precision oncology. Several epithelial tumors harbor overexpression of the trophoblast cell-surface antigen 2 (TROP-2), which represents a predictor of poor prognosis and a promising target for anticancer therapy.

Areas covered

In this review, we aim to collect the available preclinical and clinical data regarding anti-TROP-2 ADCs in lung cancer obtained through extensive literature research and screening of the available abstract/posters presented at recent meetings.

Expert opinion

Anti-TROP-2 ADCs represent an innovative upcoming weapon against both non-small cell lung cancer and small cell lung cancer subtypes, pending the results of several ongoing trials. The proper combination and placement of this agent throughout the lung cancer treatment pathway, the identification of potentially predictive biomarkers of benefit, as well as the optimal management and impact of peculiar toxicity (i.e. interstitial lung disease) are the next questions to be answered.

KEYWORDS:

• ADCs
• datopotamab deruxtecan
• non-small cell lung cancer
• small cell lung cancer
• sacituzumab govitecan
• TROP-2

1. Introduction

In the last decades, several efforts have been made to implement personalized oncology in lung cancer. The development of targeted therapies and immune checkpoint inhibitors (ICIs) have revolutionized the current treatment landscape in non-small-cell lung cancer (NSCLC), and the latter also in extensive-stage small-cell lung cancer (SCLC). Nevertheless, the need for novel therapeutical targets is still growing. The transmembrane glycoprotein Trophoblast cell-surface antigen 2 (TROP-2) plays a crucial role in carcinogenesis and tumor progression [1] and represents a fascinating therapeutical target across different tumor types. Interestingly, TROP-2 overexpression seems to be a negative prognostic factor in solid cancers [2], including NSCLC [3]. Since 2014, when the first anti-TROP-2 treatment was tested in clinical trials (PF-06664178/RN927C, a cleveable antibody-drug conjugate), several agents have been developed, including antibodies and antibody-drug conjugates (ADCs). Alongside the (relatively) novel histology-agnostic approach, the development of this new category of drugs, the ADCs, constituted by a monoclonal antibody, a linker, and a payload (cytotoxic agent) [4,5], able to specifically deliver chemotherapy to cancers cells, has blossomed. The engineering efforts, as well as the introduction of novel linkers and payloads, are leading to the development and approval of several ADCs for the treatment of solid cancers [6–9]. Of interest, the first therapy against TROP-2 approved in the United States for the treatment of metastatic triple-negative breast cancer (TNBC) is represented by an ADC (sacituzumab govitecan) [10]. Anti-TROP-2 ADCs, such as sacituzumab govitecan and datopotamab deruxtecan, have been explored in clinical trials involving patients with lung cancer, demonstrating antitumor activity and a manageable safety profile. In this review, we aim to summarize the current landscape of ADCs targeting TROP-2 in lung cancer.

2. TROP-2 structure and pathway

Tumor-associated calcium signal transducer 2 (TACSTD2), which is a member of TACSTD gene family, encodes the transmembrane glycoprotein trophoblast cell-surface antigen 2 (TROP-2) [11]. The glycoprotein TROP-2, consisting of 323 amino acids, is composed of an extracellular domain containing a thyroglobulin type-1 repeat region and an epidermal growth factor-like region, a transmembrane domain, and a cytoplasmic region [12,13]. The TROP-2 extracellular region, especially the epidermal growth factor-like domain, potentially binds growth factors, such as insulin-like growth factor 1 (IGF-1), and several other proteins (i.e. claudin-1 and −7, cyclin D1, and PKC) involved in different cellular processes [14]. The cytoplasmic tail contains a HIKE domain (responsible for protein-protein interactions), a protein kinase C (PKC) phosphorylation site, and a phosphatidyl-inositol 4,5-bisphosphate (PIP2) binding sequence, justifying the role of TROP-2 in calcium signaling [15–17]. In this light, TROP-2 is involved in several signaling pathways associated with carcinogenesis, such as the above-mentioned calcium signaling, β-catenin signaling, and fibronectin adhesion [18–20] [Figure 1]. In particular, TROP-2 promotes cell proliferation, angiogenesis, and metastatization through the activation of NF-kB and extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) kinase (MEK) signaling pathway. The activation of MAPK by the release of calcium ions induced by the interaction of inositol 1,4,5-triphosphate (IP3) and IP3 receptors, increases phosphorylated ERK 1/2 [21]. Consequently, the activator protein 1 (AP-1) transcription factor is activated [22]. Moreover, the release of Ca2+, together with diacylglycerol (DAG) derived from the hydrolysis of PIP2, promotes the activation of the NF-kB pathway [1]. TROP-2 protein is divided into two sub-products, the intracellular domain (ICD) and the extracellular domain (ECD), by intracytoplasmic enzymes, such as y-secretase and TNF-α converting enzyme (TACE). The intracellular domain with β-catenin upregulates the expression of cyclin D1 and c-myc, leading to cell growth [23]. Lastly, TROP-2 facilitates the RACK1 shift from the cytoplasm to the cell membrane, reducing the fibronectin binding to integrin β-1, thereby decreasing cell adhesion [24].

Figure 1. TROP-2 pathway (a) and mechanism of action of ADCs anti-TROP-2 (b). the TROP-2 pathway is involved in the promotion of angiogenesis, cell growth, and metastatization throughout calcium and beta-catenin signaling and through the re-localization of RACK1 (a). The mechanism of action of the three ADCs evaluated in clinical trials is reported in Figure (b), along with the so-called ‘bystanders effect’ (c).

Interestingly, Trerotola et al. demonstrated that the overexpression of the TROP-2 protein is necessary and sufficient for cancer cells growth, both in vitro and in vivo, across different tumor histologies [25]. TROP-2 promoted the metastatization process, for example, in prostate cancer, through destabilization of the fibronectin complex [11], but also in breast cancer and gastric cancer, through epithelial-to-mesenchymal transition (EMT) [26]. Moreover, the cellular localization of TROP-2 could greatly affect its role in cancer progression. In this light, in breast cancer, a fully mature intramembranous TROP-2 is associated with poor survival, while its intracellular retention leads to a better prognosis and a lower incidence of disease recurrence [27,28].

To date, no evidence has shown that the oncogenic transformation is induced by molecular alterations/mutations of TROP-2, allowing us to speculate that TROP-2-expressing cancers might be classified within the non-oncogene-addicted category.

3. TROP-2 expression in lung cancer

Several human organs express TROP-2 protein and mRNA, such as the lung, pancreas, colorectum, and skin, while the cellular location of TROP-2 expression is highly variable [25,29]. Of note, TROP-2, first discovered in trophoblastic cells, plays a crucial role in embryogenesis and fetal development [13]. Different epithelial cancers (i.e. cervical cancer, prostate cancer, thyroid cancer, urothelial cancer, head and neck cancer, lung cancer, breast cancer, carcinoid) express a high level of TROP-2 at membranous and/or cytoplasmatic level [30,31]. Moreover, TROP-2 overexpression was demonstrated to be a negative prognostic factor in several solid tumors [3,27,32–34]. In this light, a meta-analysis by Zeng et al. showed that TROP-2 overexpression was associated with poor survival in patients affected by epithelial cancers [2]. Specifically, the overexpression of TROP-2 seems to be particularly prevalent in lung cancers, ranging from over 60% of squamous cell carcinoma to 42%-64% of adenocarcinoma and 20% of high-grade neuroendocrine tumors [35,36]. Interestingly, Inamura et al. described a differential lung cancer-specific mortality according to TROP-2 overexpression across different lung cancer subtypes, highlighting an increased mortality rate in adenocarcinoma with high expression [35].

Moreover, a recent study demonstrated that, despite anticancer treatments, mainly targeted therapies and radiotherapy, can partially alter the expression of TROP-2 in patients with lung cancer, there were no significant differences in TROP-2 expression before or after specific treatments [37].

4. ADCs targeting TROP-2

Chemotherapy-based strategies represent a mainstay of solid cancers treatments, including lung cancer [38]. The idea of targeted delivery of chemotherapy was born and raised in the early 1900s when the magic bullet concept was elaborated [5]. In this light, ADCs, composed of a tumor‐specific monoclonal antibody, a chemotherapy agent, and a stable linker, allow delivering small cytotoxic molecules in tumor cells through the antibody-antigen interaction, sparing healthy tissues from cytotoxic damages [39,40]. Interestingly, despite the ‘direct’ tumor cell death due to the internalized chemotherapy agent, the apoptotic cells or ADCs could release into the extracellular space the cytotoxic component that may cause bystander cell death (‘bystanders effect’) [40] [Figure 1]. With the achievements in bioengineering, the ADCs have become more and more sophisticated, bringing different FDA approvals, firstly in hematological malignancies [6,41] and, afterward, in solid cancers [7]. This targeted approach has been tested and approved across several tumor histologies. Among these, due to the wide expression of TROP-2 in epithelial tumors, a fascinating approach is represented by the targeting of this pathway with an ADC-based approach. Along with the recent impressive results obtained with ADCs directed against human epidermal growth factor receptor 2 (HER2) in HER2-mutant NSCLC [42], the anti-TROP-2 agents in lung cancer are demonstrating very promising results [13].

4.1. Preclinical data

For effective targeting, nanocarriers able to specifically recognize the tumor cells should be designed. The preclinical studies followed this principle.

Son et al. demonstrated the activity of anti-TROP-2 antibody-conjugated nanoparticles (ST-NPs) as a potential carrier of doxorubicin in breast cancer cell lines (MDA-MB-231) [43]. Similarly, an anti-TROP-2 Fab antibody conjugated with doxorubicin (TROP-2Fab-DOX) showed promising activity in in vitro and in vivo pancreatic cancer models [44]. PF-06664178 (also known as RN927C) is an anti-TROP-2 ADC composed of an IgG1 antibody conjugated with an AcLys-VCAur0101 (PF-06380101) through a cleavable linker. Preclinical evidence in nonhuman primate toxicity studies demonstrated the linker stability, the antitumor activity of RN927C, and the capacity to minimize toxicity by avoiding the off-target release of the potent payload [45].

Sacituzumab govitecan is an ADC composed of the anti-TROP-2 monoclonal antibody sacituzumab conjugated with the topoisomerase-I inhibitor SN-38 (an irinotecan metabolite) via a cleavable CL2A linker. The payload SN-38 is a moderately cytotoxic drug and conjugated to hRS7 without affecting TROP-2 targeting and antibody pharmacokinetics [46]. After several testing in vitro and in vivo, the CL2A was selected as the preferred linker for clinical use [47]. Sacituzumab govitecan was evaluated in several xenograft models of solid cancers, including lung cancer, providing preliminary signals of activity [47]. However, in vitro, therapeutical specificity based on the antibody binding could not be demonstrated due to the extended exposure of the cytotoxicity assay to the drug [46,47]. Interestingly, no specific differences in terms of improved therapeutical response between sacituzumab govitecan and irinotecan were demonstrated in lung cancer cell lines derived from squamous cell carcinoma (SK-MES-1), maybe due to the lower flow cytometry median fluorescence intensity in these type of cells [47]. To evaluate the potential impact of TROP-2 expression on the efficacy of sacituzumab govitecan, Cardillo et al. transfected complementary DNA (cDNA) of human TROP-2 into the MDA-MB-231 TNBC cell line (typically expressing a low number of copies of TROP-2 per cell and exhibiting unresponsiveness to sacituzumab govitecan and irinotecan) [48]. The results of this analysis showed increased expression of TROP-2 into MDA-MB-231 (approximately 4-fold), correlating with improved therapeutic activity of sacituzumab govitecan [48]. Throughout preclinical studies, another issue regarding toxicity was addressed. Considering the similar expression in cancer and normal tissues of TROP-2, sacituzumab govitecan was tested in Cynomolgus monkeys, which demonstrated severe diarrhea and neutropenia. But the histological assessment demonstrated that the tissues expressing TROP-2 had minimal damage, speculating that the toxicity was related to SN-38 and not due to the TROP-2 targeting [47]. Lastly, preclinical evidence underlined the improved delivery of SN-38 through anti-TROP-2 ADC compared to Irinotecan. In particular, the concentrations of SN-38 in xenograft models showed a great improvement for the ADC compared to Irinotecan, suggesting the superiority of anti-TROP-2 antibody to deliver SN-38 [49].

SKB264, a novel anti-TROP-2 ADC, was developed using 2-methylsulfonyl pyrimidine as the linker to conjugate its payload (KL610023), a belotecan-derivative topoisomerase I inhibitor. Recently, in vitro and in vivo analyses were published, suggesting a longer half-life of SKB264, a stronger targeting effect, and better antitumor activity compared to sacituzumab govitecan [50].

Datopotamab deruxtecan (dato-DXd) is an anti-TROP-2 ADC composed of humanized anti-TROP-2 IgG1 MAb linked via a tetrapeptide-based cleavable linker to a potent topoisomerase I inhibitor payload, exatecan derivate (DXd) [51]. Due to the specific linker being cleavable only with lysosomal proteases, dato-DXd is highly stable. Despite DXd shares with SN-38, the payload of sacituzumab govitecan, the same mechanism of action, DXd is 10-fold more potent than SN-38, has an improved therapeutic index, and a longer half-life (5% of the payload released after 21 days as opposed to 90% of payload released after 3 days with sacituzumab), allowing a q21 administration schedule [52]. Okajima et al. demonstrated, in a preclinical study, the antitumor activity of dato-DXd with DNA damage induced by the accumulated DXd in TROP-2-expressing xenograft tumors, while datopotamab or an isotype control IgG ADC alone was not active [51]. dato-DXd also showed potent antitumor activity with tumor regression in several TROP-2-expressing xenograft tumors, including NSCLC patient-derived xenograft models [51].

4.2. Clinical trials

The main results of clinical trials involving ADCs anti-TROP-2 in lung cancer are summarized in Table 1. In particular, the clinical trials available are focused on three ADCs: PF 06664178 (composed of an antibody conjugated with a PF-06380101 through a cleavable linker), sacituzumab govitecan (sacituzumab conjugated with SN-38 via a cleavable CL2A linker) and datopotamab deruxtecan (composed of a monoclonal antibody linked via a cleavable linker to DXd).

Table 1. Available data regarding efficacy and safety of anti-TROP-2 ADCs in lung cancer.

Trial and reference	Phase, Design and Drug	Population	N.	Line of therapy	Clinical activity	TRAEs ≥ G3 (type, %)
King et al. [53]	Phase 1 dose-finding trial, PF-06664178	Advanced or metastatic solid tumors [19% NSCLC]	31	Pre-treated [84%, ≥ 3 lines]	Overall population: SD in 37.9%	Significant DLTs in skin and mucosa in the varying dose ranges tested
Starodub at al [54]. *	Phase I, dose escalation trial, Sacituzumab Govitecan	Advanced or metastatic solid tumors [1 pt NSCLC 2 pts SCLC]	25	Pre-treated [>50%, ≥ 3 lines]	1 patient SCLC: PR 1 patient SCLC: PD 1 patient NSCLC: SD	Tox of any grades: - Fatigue (72%) - Nausea (68%) - Diarrhea (52%) - Neutropenia (56%, 9 pts G3–4)
Heist et al. [55]*	Phase I single-arm expansion trial, Sacituzumab Govitecan	Advanced or metastatic NSCLC	54	Pre-treated [50%, ≥ 3 lines]	ORR: 19% mDOR: 6.0 mo (95% CI, 4.8–8.3) PFS ITT: 5.2 mo (95% CI, 3.2–7.1) OS ITT: 9.5 mo (95% CI, 5.9–16.7)	- Neutropenia (28%) - Diarrhea (7%) - Nausea (7%) - Fatigue (6%) - Febrile neutropenia (4%)
Gray et al. [56]*	Phase II, single-arm expansion trial, Sacituzumab Govitecan	Advanced or metastatic SCLC	53	Pre-treated [32%, ≥ 3 lines]	ORR: 14% mDOR: 5.7 mo (95% CI, 3.6–19.9) PFS ITT: 3.7 mo (95% CI, 2.1–4.3) OS ITT: 7.5 mo (95% CI, 6.2–8.8)	- Neutropenia (34%) - Fatigue (13%) - Diarrhea (9%) - Anemia (6%)
Bardia et al. [57]*	Phase I/II, single-arm dose escalation trial, Sacituzumab govitecan	Advanced or metastatic solid tumors [10.9% NSCLC 12.5% SCLC]	495	Pre-treated	NSCLC cohort: ORR: 16.7% mDOR: 6.0 mo (95% CI, 2.5–21.0) PFS ITT: 4.4 mo (95% CI, 2.5–5.4) OS ITT: 7.3 mo (95% CI, 5.6–14.6) SCLC cohort: ORR: 17.7% mDOR: 5.7 mo (95% CI, 3.6–19.9) PFS ITT: 3.7 mo (95% CI, 2.1–4.8) OS ITT: 7.1 mo (95% CI, 6.2–8.1)	- Neutropenia (42%) - Anemia (10%) - Diarrhea (8%) - Fatigue (6%) - Febrile neutropenia (5%)
Garon et al. [58]§	Phase 1 dose-escalation/expansion trial, Dato-DXd	Advanced or metastatic NSCLC	180	Pre-treated	ORR: 24% (4 mg/kg) 26% (6 mg/kg) 24% (8 mg/kg)	- Nausea (1%) - Stomatitis (2%) - Neutropenia (1%) - ILD of any grade (11%)
Garon et al. [59]§	Phase 1 dose-escalation/expansion trial, Dato-DXd	Advanced or metastatic NSCLC with actionable genomic alterations	34	Pre-treated [82%, ≥ 3 lines]	ORR: 35% mDOR 9.5 mo (95% CI, 3.3-NE)	29% (overall) Most frequent TRAEs: nausea, stomatitis, fatigue, amylase increased
Levy et al. [60]	Phase 1b, Dato-DXd plus Pembrolizumab ± platinum-based chemotherapy	Advanced or metastatic NSCLC without actionable genomic alterations	88	Untreated and Pre-treated	Overall population: ORR 37% (double therapy) ORR 41% (triple therapy) Untreated population: ORR 62% (double therapy) ORR 50% (triple therapy)	40% (double therapy) 60% (triple therapy) Most frequent TRAEs: stomatitis, nausea, decreased appetite, fatigue, anemia, ILD (4/88)

TRAEs, treatment-related adverse events; N, number; NSCLC, non-small cell lung cancer; SD, stable disease; NA, not available; pt, patient; SCLC, small cell lung cancer; ORR, objective response rate; mDOR, median duration of response; mo, months; PFS, progression-free survival; ITT, intention-to-treat population; OS, overall survival; ILD, interstitial lung disease.

* Analyses derived from IMMU-132-01 trial (NCT01631552).

§ Analyses derived from TROPION-PanTumor01 (NCT03401385).

4.2.1. PF 06664178 (RN927C)

Based on the robust preclinical evidence [45], King et al. conducted a phase I, dose-escalation trial to evaluate the safety and the activity of PF-06664178 (RN927C) in patients with pretreated advanced or metastatic solid cancers [53]. Thirty-one patients were enrolled in the trial and treated with escalating doses of PF-06664178 every 21 days (doses explored ranged from 0.15 mg/kg to 4.8 mg/kg). Among 31 patients, 6 (19%) were affected by NSCLC. Dose-limiting toxicities, such as skin rash, mucosa, and neutropenia, were observed at 3.6 mg/kg dose levels. No evidence of antitumor activity was demonstrated in the overall population, including patients with NSCLC. For these reasons, the study was prematurely discontinued [53].

4.2.2. Sacituzumab govitecan (IMMU-132)

In 2015, the results of the first-in-human trial with sacituzumab govitecan (IMMU-132) for the treatment of several pretreated advanced or metastatic epithelial cancers were published (IMMU-132-01 trial) [54]. Among 25 patients enrolled in this trial, one patient was affected by NSCLC and two by SCLC. Overall, sacituzumab govitecan demonstrated an acceptable toxicity profile and preliminary therapeutic activity in heavily pretreated solid cancers, selecting 8 and 10 mg/kg doses for phase II studies. The most commonly reported side effects (of any grade) are fatigue (72%), nausea (68%), alopecia (52%), diarrhea (52%), and neutropenia (56%). Overall, 3 patients had more than a 30% reduction in their target lesions. Among these 3 patients, one patient with SCLC (demonstrating TROP-2 expression by immunohistology of 3+) pretreated with two lines of chemotherapy demonstrated a 38% reduction in the sum of the longest diameters. No antitumor activity was shown in the other patient with SCLC, while signals of activity were noticed in the patient with NSCLC [54]. Subsequent analysis demonstrated an excellent pharmacokinetic profile, at doses of 8 and 10 mg/kg, with a low fraction of SN-38 G (glucorinidated SN-38, a component of sacituzumab govitecan), resulting in lower rates of diarrhea and a manageable toxicity profile [52]. Interestingly, an analysis regarding the uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) genotype demonstrated that patients’ UGT1A1 status was not a reliable predictor of severe diarrhea and neutropenia, although patients with the UGT1A1 × 28/*28 were more likely to experience grade≥3 neutropenia and chi-square testing indicated a statistically significant correlation between the haplotypes and grade 3 diarrhea for all patients [52]. The authors concluded that, based on no appreciable differences in safety between 10 mg/kg and 8 mg/kg sacituzumab govitecan dose level and the better response rate and duration of response related to the highest dose, 10 mg/kg is a reasonable choice for proceeding in further accrual [52].

Heist et al. reported the activity of sacituzumab govitecan (8 or 10 mg/kg on days 1 and 8 of 21-day cycles) in a single-arm expansion of the same trial in patients with advanced or metastatic NSCLC who progressed after at least one prior therapy [55]. Overall, 44 patients were enrolled in the trial, while 47, treated with a median of three prior therapies, were evaluable for the responses. The objective response rate (ORR) was 19%, with a median response duration of 6.0 months (95% CI, 4.8 to 8.3 months) and a clinical benefit rate of 43%. The median progression-free survival (PFS) in the intention-to-treat population (ITT) was 5.2 months (95% CI, 3.2–7.1 months), and the median overall survival (OS) was 9.5 months (95% CI, 5.9–16.7 months). Interestingly, among 18 patients who had received ICIs as prior therapies, 9 demonstrated objective responses (partial response or stable disease), and 5 showed durable disease control, underlying that even patients pretreated with ICIs could achieve a benefit from sacituzumab govitecan. Moreover, the majority of the tumor specimen available for immunohistochemistry (IHC) showed a strong (3+) IHC staining, suggesting that TROP-2 expression might not represent a useful predictive biomarker [55].

Another phase II dose-expansion cohort of the IMMU-132-01 trial evaluated the safety and the efficacy of sacituzumab govitecan (8 or 10 mg/kg on days 1 and 8 of 21-day cycles) in pretreated metastatic SCLC [56]. Despite the prodrug of SN-38, irinotecan, has failed to prove a benefit compared with an etoposide-containing regimen in clinical trials involving patients with SCLC [61–63], the development of an ADC able to deliver the more active metabolite of irinotecan, SN-38, brought to improved therapeutic effect, as noticed in preclinical experiences [49]. The primary endpoints of this expansion cohort were safety and ORR, while the duration of response, PFS, and OS were secondary endpoints. Among 53 patients with pretreated metastatic SCLC enrolled, 51% (n = 27) were chemosensitive, and 49% (n = 26) were chemoresistant to previous platinum-based regimens. The most frequent adverse events of all grades included diarrhea, fatigue, neutropenia, anemia, and alopecia, while neutropenia (grade 3–4) was the most frequent indication of dose reduction, which occurred in 18 patients. Among 43 patients available for outcome analysis, 26 (60%) showed a reduction in tumor size from baseline. Based on the ITT population, the ORR was 17% for those patients who received sacituzumab govitecan at the 10 mg/kg dose. The duration of response was 5.7 months (95% CI, 3.6–19.9), with a clinical benefit rate of 34%, PFS and OS of 3.7 months (95% CI, 2.1–4.3), and 7.5 months (95% CI, 6.2–8.8), respectively. Interestingly, no difference in ORR, PFS, or OS was demonstrated between chemosensitive (n = 24) and chemoresistant SCLC (n = 19). Despite the similar mechanism of action of topotecan and SN-38, inhibitors of the DNA topoisomerase-I enzyme, sacituzumab govitecan demonstrated antitumor activity in a small population of patients pretreated with topotecan (n = 15), suggesting a possible role of sacituzumab govitecan in patients refractory to topotecan. Similarly to the results presented by Heist et al. [55], no significant differences in PFS or OS were found according to the TROP-2 IHC score [56].

In 2021, Bardia et al. presented the final safety data from the overall safety population (OSP, n = 495) and efficacy results in different disease cohorts, including SCLC, of the IMMU-132-01 study [57]. This analysis confirmed neutropenia (57.8%) and diarrhea (56.2%) as the main treatment-related adverse events, demonstrating that the rate of treatment-related grade≥3 neutropenia was relevant (grade 3: 28.9%; grade 4: 13.5%). In this light, the authors elaborated recommendations for the management of severe neutropenia and diarrhea. Of note, a concerning adverse event described with other ADCs (e.g. trastuzumab deruxtecan or datopotamab deruxtecan), the interstitial lung disease (ILD), seems to be infrequent with sacituzumab govitecan. Although diarrhea did not appear to be increased in patients homozygous for UGT1A1*28/*28, this subgroup of patients had an increased risk of neutropenia with sacituzumab govitecan, underlying that patients with homozygous for UGT1A1*28/*28 should be closely monitored. Patients with SCLC experienced a longer median duration of response compared with the previous data analysis of patients receiving Sacituzumab Govitecan 10 mg/kg in this study [5.7 (n = 62) versus 4.0 (n = 36)] [56].

4.2.3. Datopotamab deruxtecan (DS-1062)

TROPION-PanTumor01 (NCT03401385) is an ongoing first-in-human phase 1 dose-escalation/expansion study evaluating datopotamab deruxtecan in patients with solid tumors. In this trial, patients with previously treated solid cancers, unselected for TROP-2 expression, are enrolled, with the primary objective being safety and tolerability. According to previously available data [64–66], the update presented at World Conference on Lung Cancer (WCLC) 2021 confirmed encouraging antitumor activity and a manageable safety profile [58]. In detail, on 8 January 2021, enrollment in the NSCLC cohort of TROPION-PanTumor01 was complete. Among 180 patients enrolled and treated with dato-DXd at 4, 6, and 8 mg/kg, the majority had previously received anti-PD-1/PD-L1 treatment and platinum-based chemotherapy (83% and 96%, respectively). Interestingly, the percentage of patients with brain metastases was particularly high (34–41%). The ORR was 24–26%. Treatment-related adverse events of all grades were observed in 30% of patients, including nausea (52%, G3: 1%), mucositis (48%, G3: 2%), and alopecia (39%, G3: 0%). Compared to sacituzumab govitecan, dato-DXd did not induce neutropenia and diarrhea, but, similarly to other ADCs, a relevant rate of ILD (n = 19, 11%).

Moreover, Garon et al. presented preliminary results in the oncogene-addicted NSCLC population enrolled in TROPION-PanTumor01 [59]. Among 34 patients affected by NSCLC harboring driver alterations, 85% showed an EGFR mutation (10% had exon 20 insertions), 9% ALK fusion, 3% ROS1 fusion, and 3% RET fusion. Most patients (82%) were heavily pretreated (41% with ICIs, 91% with platinum-based chemotherapy, and 85% with tyrosine kinase inhibitors). Clinical activity was observed in NSCLC with EGFR common mutations (Ex19del and L858R), including osimertinib pretreated patients, and across other molecular alterations, demonstrating an ORR of 35% and a median duration of response of 9.5 months. The safety profile was consistent with previous results, reporting nausea and mucositis as the most common adverse events, often of low grade (grade 1/2). Based on these encouraging results, dato-DXd is currently under evaluation in oncogene-addicted NSCLC (EGFR mutations including exon 20 insertions, ALK, ROS1 and RET fusions, BRAF mutations, NTRK rearrangements, and MET exon 14 skipping alterations) after targeted therapies and platinum-based chemotherapy (TROPION Lung05; NCT04484142).

The preliminary results of the TROPION-Lung02 phase 1b trial were presented at the 2022 WCLC. A promising clinical activity and a tolerable safety profile of dato-DXd in combination with pembrolizumab with or without platinum chemotherapy were observed in patients with previously untreated or pretreated advanced NSCLC without actionable genomic alterations [60]. The ORR in the overall population was 37% among 38 patients receiving dato-DXd in combination with pembrolizumab (doublet therapy) and 41% among 37 patients receiving dato-DXd in combination with pembrolizumab and platinum chemotherapy (triplet therapy). A disease control rate (DCR) of 84% was demonstrated with both the double and triple combination therapy in the overall population, including in first-line and second-line settings. In previously untreated patients, an ORR of 62% (eight out of 13 patients receiving doublet therapy) and 50% (10 out of 20 patients receiving triplet therapy) were observed. The double therapy showed a DCR of 100%, while in the triplet therapy, the observed DCR was 90%. Regarding treatment-emergent adverse events, Grade 3 or greater events were registered in 40% and 60% of patients in the doublet and triplet cohorts, respectively. The most prevalent any-grade adverse events observed in the doublet and triplet cohorts were: stomatitis (56% and 29%), nausea (41% and 48%), decreased appetite (28% and 38%), fatigue (25% and 36%) and anemia (16% and 36%). Overall, four ILD were described to be drug-related by an independent adjudication committee across both cohorts, two grade 1/2 and two grade 3.

5. Ongoing trials

Several trials are currently ongoing to further explore the safety/efficacy of ADCs anti-TROP-2 in lung cancer and the optimal sequences/combinations within the current treatment landscape [Table 2].

Table 2. Ongoing trials involving anti-TROP-2 ADCs in lung cancer (clinical trials.Gov accessed on January 18, 2023).

ClinicalTrial.gov ID	Phase	Setting	N	Treatment arms	Primary endpoint	Selected secondary endpoints	Status
TROPiCS-03 (NCT03964727)	2	Metastatic solid tumors (NSCLC progressed after platinum-based chemotherapy and anti-PD(L)1)	165	Sacituzumab govitecan	ORR by IA	ORR by BIRC, DOR, CBR, PFS	Recruiting
EVOKE-01 (NCT05089734)	3	Advanced or metastatic NSCLC with progression on or after platinum- chemotherapy and immunotherapy	520	Sacituzumab govitecan vs docetaxel	OS	PFS, ORR, DOR, DCR, TEAEs	Recruiting
EVOKE-02 (NCT05186974)	2	First Line, advanced or metastatic NSCLC without actionable genomic alterations.	164	Sacituzumab govitecan plus pembrolizumab ± platinum-based chemotherapy	ORR by BIRC DLTs	PFS, OS, DOR, DCR, TEAEs	Recruiting
KEYNOTE D46/EVOKE-03 (NCT05609968)	3	First-line, PD L1 TPS≥50% Metastatic NSCLC	614	Sacituzumab govitecan plus pembrolizumab vs pembrolizumab	PFS by BIRC, OS	OR, DOR, Quality of Life	Not yet recruiting
TROPION-PanTumor01 (NCT03401385)	1	Advanced or metastatic solid tumors (Including treatment naïve NSCLC)	770	Datopotamab deruxtecan (dose escalation and dose expansion cohorts)	DLT, AEs, G>/ = 2 mucositis/stomatitis	Cmax, Tmax, AUC	Recruiting
TROPION-PanTumor02 (NCT05460273)	1/2	Advanced or metastatic solid tumors (Including pretreated NSCLC)	118	Datopotamab deruxtecan	ORR by BICR	ORR by IA, DOR, DCR, BoR, TTR, PFS, OS, TEAE and AESI, Immunogenicity of Dato-DXd	Recruiting
ICARUS-LUNG01 (NCT04940325)	2	Advanced and/or unresectable NSCLC, II to IV line	100	Datopotamab deruxtecan	ORR by IA	DOR, PFS, CBR, AEs	Recruiting
TROPION-Lung01 (NCT04656652)	3	Previously treated advanced or metastatic NSCLC with or without actionable genomic alterations	590	Datopotamab deruxtecan vs Docetaxel	PFS by BIRC, OS	PFS by IA, ORR, DOR, DCR, TTR, TTD	Recruiting
TROPION-Lung02 (NCT04526691)	1b	Advanced or metastatic NSCLC, previously treated or are treatment naïve in I line	140	Datopotamab deruxtecan plus Pembrolizumab ± platinum-based chemotherapy	DLT, TEAEs	ORR, DOR, PFS, OS	Recruiting
TROPION-Lung04 (NCT04612751)	1b	Advanced or metastatic NSCLC who are either treatment-naïve or have received 1 prior line without ICI	232	Datopotamab deruxtecan plus immunotherapy (Durvalumab, AZD2936, MEDI5752) ± carboplatin	DLTs; TEAEs and other safety parameters	ORR, DOR, DCR, PFS, TTR, OS	Recruiting
TROPION-Lung05 (NCT04484142)	2	Advanced or metastatic NSCLC with actionable genomic alterations and progressed on or after targeted therapy and platinum-based chemotherapy	137	Datopotamab deruxtecan	ORR by BIRC	DOR, PFS, OS, TEAEs, Pharmacokinetic Parameters	Active, not recruiting
TROPION-Lung07 (NCT05555732)	3	Advanced or metastatic NSCLC treatment naïve	975	Datopotamab deruxtecan plus pembrolizumab vs pembrolizumab plus platinum-based chemotherapy	PFS by BIRC OS	ORR, PFS by IA, ORR, DOR, TTR, DCR, PFS2	Not yet recruiting
TROPION-Lung08 (NCT05215340)	3	Untreated advanced or metastatic NSCLC expressing PD L1 TPS≥50%	740	Datopotamab deruxtecan plus pembrolizumab vs. pembrolizumab	PFS by BIRC OS	ORR, PFS, PFS2, ORR, DOR, TTR, DCR, TTD, TEAE	Recruiting
ORCHARD (NCT03944772)	2	Advanced or metastatic EGFR mutant NSCLC with progression on frontline osimertinib	250 (all platform)	Datopotamab deruxtecan plus osimertinib	ORR	PFS, DOR, OS	Recruiting
A264 (NCT04152499)	1/2	Locally advanced unresectable/metastatic solid tumors who are refractory to available standard therapies (Including NSCLC)	430	SKB264	Phase 1: MTD, RDEs Phase 2: ORR	Phase I: DLTs, Safety and tolerability profile, ORR, DOR, PFS, OS. Phase II: Safety and tolerability profile, DOR, PFS, OS, Levels of TROP2 in tumor	Recruiting

N, number – estimated enrollment; NSCLC, non-small cell lung cancer; PFS, progression-free survival; BIRC, blinded independent central review; DCR, disease control rate; PFS2, PFS on the next line of treatment; ORR, objective response rate; DOR, duration of response; IA, investigator-assessed; AE, Adverse event, CBR, clinical benefit ratio; ICI, immune-checkpoint inhibitor; BoR, Best Overall Response; TTR, Time To Response; TEAE, treatment-emergent adverse event; AESI, adverse event of special interest, DLT, Dose Limiting Toxicities; MTD, Maximum Tolerated Dose; RDE, Recommended Doses for Expansion; G, Grade; Cmax, Maximum concentration; Tmax, Time at which Cmax is reached, AUC, Area under the drug concentration-time curve, TTD, Time to Deterioration; CBR, Clinical Benefit Rate.

EVOKE-01 (NCT05089734) is an ongoing open-label, randomized, phase 3, evaluating the efficacy of sacituzumab govitecan versus docetaxel in patients with advanced NSCLC after platinum-based chemotherapy and anti-PD1/PD-L1 either in combination or sequentially. OS is the primary endpoint, and the estimated primary completion date is set by May 2024.

The combination of sacituzumab govitecan with pembrolizumab or pembrolizumab and a platinum agent will be evaluated in the randomized, open-label, phase 2 trial EVOKE-02 (NCT05186974). ORR and the definition of the recommended Phase 2 dose are the two co-primary endpoints of the study.

Moreover, KEYNOTE D46/EVOKE-03 (NCT05609968) is a randomized, open-label, phase 3 study to evaluate the efficacy and safety of pembrolizumab in combination with sacituzumab govitecan versus pembrolizumab alone in patients with advanced NSCLC and PDL1 ≥ 50%. The PFS and OS are co-primary endpoints.

Regarding datopotamab deruxtecan, TROPION-Lung02 (NCT04526691) is a phase 1b study designed to assess the safety and activity of dato-DXd in combination with pembrolizumab with or without 4 cycles of platinum chemotherapy in advanced NSCLC patients. Encouraging results of the interim analysis were recently presented [60], while the completion date is expected to be by the end of December 2023.

Another phase 1b study evaluating the safety and tolerability of dato-DXd is the TROPION-Lung04 (NCT04612751), intending to evaluate dato-DXd in combination with different types of immunotherapeutic agents (durvalumab, AZD2936, or MEDI5752) with or without 4 cycles of carboplatin in first- or second-line.

Similarly, TROPION-Lung07 (NCT05555732) and TROPION-Lung08 (NCT05215340) are two randomized, open-label, phase 3 studies that are evaluating the efficacy and safety of dato-DXd in combination with pembrolizumab. TROPION-Lung07 will evaluate dato-DXd plus pembrolizumab versus pembrolizumab plus platinum-based chemotherapy in patients with PD-L1 < 50% advanced NSCLC without actionable genomic alternations. On the other hand, TROPION-Lung08 is evaluating dato-DXd plus pembrolizumab versus pembrolizumab alone in patients with advanced NSCLC and PD-L1 ≥ 50% and is currently recruiting participants. Both trials are currently enrolling patients who were not previously treated and shared PFS and OS as primary endpoints.

As above-mentioned, due to the results presented in patients with oncogene-addicted NSCLC enrolled in TROPION-PanTumor01 [59], phase 2 TROPION-Lung05 (NCT04484142) is ongoing to evaluate the activity and safety of dato-DXd in advanced NSCLC with actionable genomic alterations and progressed on or after targeted therapy and platinum-based chemotherapy.

Moreover, a specific cohort of the ORCHARD platform trial enrolls EGFR-mutant NSCLC with progression on osimertinib, which will be allocated to dato-DXd plus osimertinib with primary endpoint ORR.

Finally, a phase 1/2, first-in-human clinical trial evaluating SKB264 in patients with advanced solid tumors, including NSCLC and SCLC, who are refractory to available standard therapies, is currently recruiting (NCT04152499).

6. Conclusion

Anti-TROP-2 ADCs, mainly sacituzumab govitecan and datopotamab deruxtecan, demonstrated a promising antitumor activity with a tolerable safety profile in advanced NSCLC without oncogenic driver alterations in oncogene-addicted NSCLC, and in SCLC. Several studies are ongoing to validate these preliminary results and to find the optimal placement of ADCs in the current and future lung cancer treatment landscape.

7. Expert opinion

In the current era of precision oncology, the development of ADCs anti-TROP-2 has led to important approval in solid tumors, such as in triple-negative breast cancer [10] and urothelial cancers [9]. Preliminary data available in lung cancer are very promising and generated the scientific community’s interest while raising important questions. The first is related to the identification of predictive biomarkers. Despite the overexpression of TROP-2 in epithelial cancers, including lung cancer, represents a negative prognostic factor, to date, only limited and inconclusive data regarding the potential predictive role of TROP-2 expression for TROP-2-directed targeted therapy are available. Although Cardillo et al. demonstrated that an increased expression of TROP-2 in breast cancer cell lines correlates with improved antitumor activity with sacituzumab govitecan [48], the single-arm expansion of IMMU-132-01 trial in patients with advanced and pretreated NSCLC showed that more than 90% of available tumor specimens were highly positive of TROP-2 IHC, suggesting that TROP-2 staining might not represent a useful predictive biomarker [55]. Indeed, patient selection represents a crucial point regarding the use of ADCs anti-TROP-2. The expression level of TROP-2 is a continuous variable, suggesting that, potentially, patients should be prescreened and excluded from treatment based on antigen expression at a particular level. Some ongoing trials evaluating anti-TROP-2 ADCs could, at least in part, respond to this unresolved question, potentially evaluating other biomarkers, such as topoisomerase 1 protein [67]. The second open question is related to the safety/activity of combining ADCs with other therapeutical agents. The ADCs and immunotherapy combination appears to be particularly intriguing. Indeed, immunotherapy could lead to an improvement of anti-tumor immunity induced by ADCs, increasing immune effector function and cell-mediated tumor recognition [4]. Despite several trials are currently ongoing to elucidate the role of anti-TROP-2 ADCs and immunotherapy combinations [Table 2], only a few data are available so far. The results of the interim analysis of the TROPION-Lung02 trial showed encouraging results with the combination of dato-DXd plus pembrolizumab (even without chemotherapy), particularly in the first-line setting. The updated results of this trial, as well as the novel information coming from the ongoing trials, will unravel the potentialities of the combination of anti-TROP-2 ADCs and immunotherapy, shedding light on the potential best therapeutical approach (type of immunotherapeutic agent in combination, the role of chemotherapy, combined versus sequential approach). On the other hand, despite encouraging results of dato-DXd monotherapy from TROPION-PanTumor01 in patients with oncogene-addicted NSCLC [59], no data are currently available in terms of the combination of anti-TROP-2 ADCs and targeted therapies. An answer to this unmet need could derive from an ongoing phase 2 platform ORCHARD study, evaluating the activity of adding dato-DXd to osimertinib in EGFR-mutant NSCLC progressed to frontline osimertinib [68]. Of interest, anti-TROP-2 ADCs might represent an interesting option for still orphan subtypes of lung cancer, such as refractory/relapsed SCLC. Finally, although some agents already approved for lung cancer are associated with the risk of developing pulmonary toxicities, the appropriate management, treatment algorithm, and follow-up of ADCs-related ILD is still to be defined, especially in the light of the upcoming combinatorial strategies with other agents.

Article highlights

• TROP-2 overexpression is associated with poor survival in solid cancers, including lung cancer

• Antibody-drug conjugates (ADCs) represent a novel and promising approach in lung cancer

• Sacituzumab govitecan and datopotamab deruxtecan, anti-TROP-2 ADCs, have demonstrated clinical activity and manageable safety profile

• Sacituzumab govitecan demonstrated activity also in pretreated small cell lung cancer, while datopotamab deruxtecan showed benefit in pretreated oncogene-addicted non-small-cell lung cancer

• Several trials are ongoing to explore the safety/efficacy of ADCs anti-TROP-2 and the optimal sequences/combinations within the current treatment landscape in lung cancer

Declaration of interest

L Belluomini declares speakers’ fees from AstraZeneca, MSD and Roche outside the submitted manuscript and travel fees from Takeda. S Pilotto declares honoraria and/or speakers’ fees from AstraZeneca, Eli Lilly, BMS, Merck, Takeda, Amgen, Novartis and Roche outside the submitted manuscript The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

A reviewer on this manuscript has disclosed that they are an inventor of sacituzumab govitecan and are eligible to receive compensation from Gilead Sciences for sales revenue. Peer reviewers on this manuscript have no other relevant financial relationships or otherwise to disclose.

Additional information

Funding

This paper was not funded.