Ilixadencel, a Cell-based Immune Primer, plus Sunitinib Versus Sunitinib Alone in Metastatic Renal Cell Carcinoma: A Randomized Phase 2 Study

Take Home Message Intratumoral injection of ilixadencel, consisting of proinflammatory allogeneic dendritic cells, before nephrectomy, followed by sunitinib treatment after nephrectomy showed a trend for improved tumor response rate and overall survival, compared with sunitinib monotherapy.


Introduction
Metastatic renal cell carcinoma (mRCC) remains a clinical challenge despite recent developments in oncologic treatment option. In particular, improved treatment is urgently needed for the 17-20% individuals diagnosed with synchronous metastases and classified as poor-or intermediate-risk patients according to the International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) [1,2].
Tyrosine kinase inhibitors (TKIs) targeting vascular endothelial growth factor (VEGF) and related tyrosine kinases have been the cornerstone of medical treatment for mRCC until recently [3,4]. However, most patients treated with a TKI agent as monotherapy ultimately develop resistance. The era of immune checkpoint inhibitors (ICIs) has recently opened new treatment perspectives, and combination treatments with ICIs with or without a TKI are now recommended as first-line treatment [5][6][7][8][9][10].
Ilixadencel is a cell-based, off-the-shelf investigational drug product based on allogeneic monocyte-derived inflammatory cells aimed to prime an adaptive anticancer immune response by recruiting and activating endogenous cross-presenting dendritic cells (DCs) when injected intratumorally [11][12][13]. Preclinical in vitro studies with ilixadencel have shown that ilixadencel produces factors that induce phenotypic maturation of allogeneic bystander DCs and enhances their ability to cross-present cell-associated antigens to CD8 + T cells [12,13]. Moreover, local subcutaneous injection of allogeneic mouse-ilixadencel in mice has been shown to induce migration of endogenous DCs to draining lymph nodes and systemic activation of antigen-specific CD8 + T cells [11]. In line with these preclinical data, the majority of evaluable patients (11/15) with hepatocellular carcinoma (HCC) treated with intratumoral injections of ilixadencel [14] showed an increased frequency of interferon-gamma-producing CD8 + T cells specific for the HCC-associated tumor antigens hTERT and/or AFP. The initial phase 1 data in 12 patients with newly diagnosed synchronous mRCC suggested that ilixadencel treatment before nephrectomy followed by standard sunitinib treatment after nephrectomy was feasible [15]. Based on these results, we designed a randomized, phase 2, open-label, multicenter trial comparing intratumoral ilixadencel before nephrectomy followed by sunitinib with standard of care sunitinib monotherapy after nephrectomy, in patients with synchronous mRCC in the first-line setting.

Study design
Patients were randomized in a 2:1 ratio to ilixadencel (two intratumoral doses of ilixadencel in the primary tumor before nephrectomy) followed and adequate end-organ and bone marrow function, and were without any significant comorbidities. Patients with known brain metastases following metastasis-directed local treatment were eligible provided that there were no indications of either clinical or radiological progression before the initiation of the study.
The patients provided written informed consent.

Randomization
Patients were stratified according to the IMDC criteria (high vs intermediate risk) and randomized in a 2:1 ratio to receive either ilixadencel plus sunitinib or sunitinib alone. Treatment allocation was not masked, and patients received information about study design and the allocated treatment.

Outcomes
The coprimary endpoints were 18-mo survival rate and overall survival (OS), both for intention-to-treat and separately by IMDC risk groups. OS was defined as the time from the date of randomization to the time of death from any cause or to the last follow-up for alive patients. The key secondary endpoints were objective response rate (ORR; independent blinded central review), confirmed ORR (amended post hoc analysis based on independent blinded central review data), and progression-free survival (PFS), defined as the time from sunitinib start to the time of progressive disease according to RECIST 1.1 [16] or death following sunitinib initiation from any cause, whichever occurred first. Safety assessment included all randomized patients. Safety data were monitored by an independent data and safety monitoring committee.

Statistical analysis
As this study was exploratory, sample size was not based on power cal-  Fig. 1.
Overall, the treatment groups were balanced with respect to baseline demographic and disease characteristics ( Table 1).
In the ILIXA/SUN group (n = 56), ten patients never received sunitinib and one patient did not undergo follow-up CT. In the SUN group, five patients never received sunitinib. Death within 2 mo after surgery was the most frequent reason for not starting sunitinib (five patients in the ILIXA/SUN arm and three in the SUN arm). Additional reasons included disease progression (n = 3), withdrawal (n = 1), different diagnosis at laparotomy (n = 1), start of another treatment after nephrectomy (n = 1), and withdrawal of consent (n = 1). The safety population included all 88 randomized patients.
At the last survival follow-up, the number of patients still alive in the ILIXA/SUN arm was 22 of 55 (40.0%), compared with nine of 30 patients in the SUN arm (30.0%; odds ratio 2.0, 95% CI 0.8-5.1; p = 0.14). One additional patient was alive at 18 mo but was lost to subsequent survival follow-up.
The The median PFS from the start of sunitinib treatment in the ILIXA/SUN arm was 11.8 mo, as compared with 11.1 mo in the SUN arm (p = 0.55).
The confirmed ORR was 42.2% (19/45) in the ILIXA/SUN arm, including three patients with complete response (CR; Table 2). Among the three patients with a confirmed CR, the sum of tumor diameter in the target lesions were 22 mm (adrenal), 43 mm (lung Â 2, muscle, and lymph node), and 22 mm (lung Â 2), prior to treatment. Two additional patients in the ILIXA/SUN arm developed a CR at the last follow-up CT scan at 18 mo; one had stable disease until the CR and the other had a partial response after 3 mo until the CR was recorded at 18 mo. The ORR in the SUN arm was 24.0% (six/25; p = 0.13) with no confirmed CR. One patient in the SUN arm had a CR observed at the last 18-mo CT follow-up.
The five ILIXA/SUN patients who achieved a CR (three confirmed and two nonconfirmed) were all alive at the latest survival follow-up, while the SUN patient with nonconfirmed CR died. In high-risk patients, the confirmed ORR was 38.5% for the ILIXA/SUN arm and 33.3% for the SUN arm (p = 0.83). In the intermediate-risk group, the corresponding rates were 43.8% in the ILIXA/SUN arm and 21.1% in the SUN arm, respectively (p = 0.1).

3.3.
Sunitinib treatment: median duration, drug dose reduction, or interruption The median duration of sunitinib treatment in the ILIXA/ SUN arm was 6.9 (95% CI 6.0-9.3) mo, and it was 7.8 (95% CI 5. 8-10.4)   AEs were reported, that is, AE of a certain type was counted only once in each patient. In both groups, the most common AEs of any cause and the most common AEs related to treat-ment were fatigue, diarrhea, and nausea (see Table 3). Grade !3 anemia was slightly more common in patients in the ILIXA/SUN arm (5.2%) than in those in the SUN arm (3.3%). Anemia was not related to any vaccination procedures, but was judged due to disease progression (n = 2) and sunitinib treatment (n = 1) in the ILIXA/SUN arm and postoperative anemia in one patient in the SUN arm. Grade 3 AEs occurred in 48 of all 88 patients enrolled (54.5%), 31 in the ILIXA/SUN arm and 17 in the SUN arm. Nine patients (10.2%) experienced a grade 4 AE, six in the ILIXA/SUN arm and three in the SUN arm. Overall, two patients (2.3%) discontinued the study due to an AE of any cause, one patient in the ILIXA/SUN arm and one in the SUN arm. Twelve patients (13.6%) discontinued due to death during the study, seven patients in the ILIXA/SUN arm and five in the SUN arm.      Table 4). Two patients developed a grade 3 AE that was attributed to ilixadencel, whereas five patients had a grade 3 AE that was considered related to sunitinib. One patient in the SUN arm died due to septic shock of abdominal origin that was attributed by the investigator to the treatment of sunitinib (1.1%). There were no grade 4 and 5 events related to treatment with ilixadencel.

Discussion
This trial was a randomized, phase 2, open-label study comparing intratumoral ilixadencel followed by sunitinib with sunitinib monotherapy (standard of care at the time of the study), in patients with synchronous mRCC in the firstline setting. Upfront nephrectomy was performed in both groups (following ilixadencel vaccination in the experimental arm). The drug combination did not improve OS compared with sunitinib alone. These statistically negative OS data are in line with the data from a recently published phase 3 study in a patient population with synchronous mRCC using autologous monocyte-derived DCs loaded with mRNA from the autologous tumor plus sunitinib versus sunitinib alone, where no improvement in median OS was observed [17]. Nevertheless, ilixadencel in combination with sunitinib was associated with a numerically higher rate of confirmed responses (42.2%) including 6.7% CR (all alive at the last follow-up) compared with 24% with a confirmed response (none with a confirmed CR) in patients treated with sunitinib monotherapy. The observed responses seemed to be driven mainly by intermediate-risk patients. The short survival of poor-risk patients in both arms is consistent with more recent finding from phase 3 randomized clinical trials, indicating that upfront nephrectomy should be avoided in this subgroup due to the risk of rapidly progressive disease [18,19]. Of possible interest, while the OS rate at 18 mo was comparable in both arms, the OS curves separated thereafter. This might indicate a possibility of late responses with prolonged duration in the ILIXA/SUN arm. Indeed, remarkably late CRs (18 mo) were noted in two patients treated with the combination. Furthermore, the nearly two-fold higher rate of confirmed objective responses in the ILIXA/ SUN patients, as compared with sunitinib alone, may be clinically meaningful. Our hypothesis is that ilixadencel induces a systemic and sustained activation of tumorspecific T cells and that the subsequent blockade of different VEGF-dependent immunosuppressive mechanisms by sunitinib will unleash the full antitumor potential of an ilixadencel-induced systemic and sustained tumorspecific, T-cell response. Such a proposed synergistic mechanism is supported by data from others showing that sunitinib works in concert with immune primers and anticancer vaccines, including DC-based vaccines in preclinical tumor models [20][21][22].
The addition of ilixadencel to sunitinib did not increase toxicity, and the safety profile was consistent with previous experience with ilixadencel in combination with TKIs in mRCC [15], HCC [14], and gastrointestinal stromal tumors [23]. The schedule of sunitinib was in line with previous randomized trials with sunitinib [5,9]. The incidence of grade 3 and 4 events was similar in both arms, whereas no treatment-related deaths occurred in the ILIXA/SUN arm.
The present study has several limitations, including a small sample size and absence of blinding, as expected for a phase 2 trial using an interventional procedure. A nonnegligible proportion did not proceed to sunitinib treatment, introducing a potential selection bias. Moreover, exploratory in its design, the trial was not adequately pow-ered to detect modest differences in survival. The present study population of patients with synchronous metastases could possibly have diminished sensitivity, in particular since both arms included a substantial number of high-risk patients who may not have benefitted from the treatment approach with upfront nephrectomy [18,19]. Moreover, since patient survival was the only postprogression parameter recorded, potential differences in secondline treatment between the groups cannot be excluded. In addition, the standard of care has evolved since the time this trial was conceived, and sunitinib monotherapy is currently recommended only as first-line medical therapy in intermediate-and poor-risk mRCC patients who cannot receive or tolerate immune checkpoint inhibition [7]. The present study was limited to synchronous mRCC due to the study design, indicating that most patients would have remained unbenefited even with positive study results. Nevertheless, patients with synchronous metastatic RCC represent a vulnerable group of RCC patients in whom good treatment options were largely lacking, motivating our trial design. Future trials of ilixadencel in mRCC should therefore use ICI-based combinations as backbone regimens. Based on the results of the present study, The US Food and Drug Administration has recently supported further development of the ilixadencel and sunitinib combination with a Regenerative Medicine Advanced Therapy designation [24].

Conclusions
In conclusion, despite that this trial failed to meet its primary endpoints, it showed the combination of ilixadencel with sunitinib to be safe and associated with promising overall and CR rates, compared with sunitinib alone. Future investigations of ilixadencel with regimens combining ICIs and TKIs in the study population are warranted.
Author contributions: Magnus Lindskog had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Lindskog, Suenaert, Karlsson-Parra, Ljungberg.  relevant to the subject matter or materials discussed in the manuscript (eg, employment/affiliation, grants or funding, consultancies, honoraria, stock ownership or options, expert testimony, royalties, or patents filed, received, or pending), are the following: Alex Karlsson-Parra and Peter Suenaert report ownership of stocks in Immunicum AB. Alex Karlsson-Parra is an Immunicum employee, and Peter Suenaert is an Immunicum consultant. All other authors report no conflict of interest.
Funding/Support and role of the sponsor: The research reported is sponsored by Immunicum AB.
Ethics statement: This study was approved by the Independent Ethics Committee and the Institutional Review Board prior to inclusion of patients. Patients provided written informed and signed consent before participation.
Data sharing: No identifiable data will be shared and should not be requested. The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.