Abstract P3-06-01: Unleashing NK- and CD8 T cells by combining monalizumab (anti-NKG2A) and trastuzumab for metastatic HER2+ breast cancer: first results MIMOSA trial

Background Although treatment options and survival of HER2+ metastatic breast cancer (MBC) patients have greatly improved, the majority of MBC-patients still die of this disease. The relatively high levels of TILs observed in this BC subtype provide a rationale for immunomodulatory strategies, however, PD1-blockade has only shown modest response rates in this setting. While PD-1 blockade mainly acts on T cells, monalizumab targets the inhibitory immune checkpoint NKG2A which interacts with HLA-E on tumor cells, thereby unleashing NK- as well as CD8 T cells. We hypothesize that monalizumab can promote antibody-dependent cell-mediated cytotoxicity (ADCC) which is critical for trastuzumab efficacy. Clinical activity was shown in patients with head and neck cancer when monalizumab was combined with cetuximab (anti-EGFR). Here, we present the first results of the MIMOSA-trial investigating the efficacy of the novel combination monalizumab and trastuzumab in patients with HER2+ MBC. Methods In the phase II MIMOSA-trial (NTC04307329), HER2+ MBC patients were treated biweekly with 4mg/kg trastuzumab and 750mg monalizumab. Key eligibility criteria were progressive disease despite anti-HER2 therapy, had received a minimum of one and a maximum of three lines of palliative chemotherapy, had measurable disease according to RECIST1.1, and a serum LDH-level below 500U/L. Primary endpoint was objective response rate according to RECIST1.1. Secondary endpoints included clinical benefit rate (complete response CR, partial response PR or stable disease SD for at least 6 months) according to RECIST1.1, progression-free survival, overall survival and safety. Dose-limiting toxicities were continuously monitored throughout the trial and evaluated using a pre-defined Pocock-type boundary rule. Following a Simon’s two-stage design, 11 patients were included in stage I of the trial. If two or more responders were observed, further exploration is warranted in stage II. Results Between January 2021 and April 2022, eleven women of which ten are currently evaluable were enrolled in the trial. Patients received a median of two lines of prior treatment for MBC, of which 6 out of 11 patients were treated with trastuzumab emtansine (T-DM1). The majority of patients had hormone receptor positive BC (72% of the patients) and had low levels of tumor-infiltrating lymphocytes (TILs) with a median of 1% (ranging from 1% to 20%). Patients received a median of four cycles of trastuzumab and monalizumab. Treatment was well tolerated with no dose-limiting toxicities. No objective responses were observed in the first ten out of eleven evaluable patients. Therefore, MIMOSA stage I did not meet its primary endpoint, leading to discontinuation of the trial. Conclusions The novel combination of trastuzumab and monalizumab did not induce objective responses in heavily pre-treated HER2+ MBC patients.

Citation Format: Veerle Geurts, Leonie Voorwerk, Karolina Sikorska, Roberto Salgado, Koen van de Vijver, Marloes van Dongen, Inge Kemper, Ingrid A. Mandjes, Martine Heuver-mes, John Haanen, Gabe S. Sonke, Hugo Horlings, Marleen Kok. Unleashing NK- and CD8 T cells by combining monalizumab (anti-NKG2A) and trastuzumab for metastatic HER2+ breast cancer: first results MIMOSA trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-06-01.

Novel SGLT2 inhibitor: first-in-man studies of antisense compound is associated with unexpected renal effects

The antisense compound ISIS 388626 selectively inhibits renal glucose reabsorption by inhibiting the sodium–glucose cotransporter‐2 (SGLT2) mRNA expression. It is developed as an insulin‐independent treatment approach for type 2 diabetes mellitus (T2DM). The safety, tolerability, pharmacokinetics, and pharmacodynamics after subcutaneous administration of the drug were planned to be evaluated in healthy volunteers in a single‐ascending‐dose study (50–400 mg) and a multiple‐ascending‐dose study (6 weeks; weekly doses of 50–400 mg with loading dose regimen of three doses during the first week). The study was halted early because increases in serum creatinine occurred in the subjects participating in the 100 mg multiple‐dose cohort. The pronounced changes in serum creatinine were accompanied by increased urinary excretion of beta‐2‐microglobulin and KIM1. The possible mechanisms for these findings remain elusive and are in contrast to preclinical findings as comparable treatment with ISIS 388626 of animals did not reveal similar changes. Although exposure was limited, there was an indication that glucosuria increased upon active treatment. Before the concept of antisense‐mediated blocking of SGLT2 with ISIS 388626 can be explored further, more preclinical data are needed to justify further investigations.

Renal Effects of Antisense-Mediated Inhibition of SGLT2

ISIS 388626 is an antisense sodium-glucose cotransporter 2 (SGLT2) inhibitor designed to treat type 2 diabetes mellitus by induction of glucosuria. ISIS 388626 was demonstrated to be safe and effective in preclinical trails in several species. We undertook the present study to evaluate the safety and efficacy of 13 weekly doses of 50, 100, and 200 mg of ISIS 388626 in humans. ISIS 388626 increased 24-hour urinary glucose excretion dose dependently with 508.9 ± 781.45 mg/day in the 100-mg and 1299.8 ± 1833.4 mg/day in the 200-mg cohort, versus 88.7 ± 259.29 mg/day in the placebo group. ISIS 388626 induced a reversible increase in serum creatinine, with the largest effect after eight doses of ISIS 388626 (200 mg; 0.38 ± 0.089 mg/dl; 44% increase over baseline). Three subjects were discontinued as a result of creatinine increases. The renal clearance test revealed no indications for impairment of glomerular filtration or renal perfusion. The creatinine increases were accompanied by a rise in the levels of urinary renal damage markers [β-2-microglobulin (B2M), total protein, kidney injury molecule (KIM1), α-glutathione S-transferase (aGST), N-acetyl-β-(d)-glucosaminidase (NAG)]. Other treatment-related adverse events included mild injection site reactions occurring in 8-19% of the subjects. In conclusion, ISIS 388626 treatment induced glucosuria at a dose level of 200 mg/week. This intended pharmacological effect was small, amounting to approximately 1% of the total amount of filtered glucose. Changes in serum and urinary markers were indicative of transient renal dysfunction, most probably of tubular origin. Whether the glucosuria is caused by specific SGLT2 inhibition or general tubular dysfunction or a combination remains uncertain.