MDM2 Inhibition with Alrizomadlin (APG-115) in TP53 wild-type salivary gland cancers: a phase I clinical trial

Domain: biology
Published: 2026-03-19
Editorial outcome: minor_revision

Abstract
Preclinical studies have evaluated murine double minue 2 (MDM2) inhibitors as a treatment for
adenoid cystic carcinoma (ACC), but clinical trials are lacking. This phase I trial
(NCT03781986) assesses the safety and antitumor activity of an oral MDM2 inhibitor,
alrizomadlin (APG-115), +/- carboplatin in TP53 wild type unresectable recurrent/metastatic
salivary gland cancers (R/M SGC) with a planned 1:1 randomization to carboplatin
chemotherapy. The co-primary endpoints are determination of dose-limiting toxicity (DLT) and
response rate (RR) for alrizomadlin monotherapy +/- carboplatin. Secondary endpoints include
safety, survival, and RR by tumor histology. After enrollment of 4 patients to combination
therapy, the trial was modified to a single arm study of alrizomadlin monotherapy due to excess
toxicity. 1 DLT was seen in the combination arm, all patients had > G3 treatment related
adverse events (TRAE). 37 patients were enrolled to alrizomadlin monotherapy. 3 DLTs were
encountered, 67% of patients had > G3 TRAE. The RR was 15% with median progression free
survival 10.5 months. These findings demonstrate encouraging tolerability of alrizomadlin
monotherapy with antitumor activity in patients with TP53 wild type SGC, especially ACC.

Introduction
Malignant salivary gland cancers (SGC) are a rare site of head and neck tumors
accounting for approximately 6-8% of primary head and neck cancers1. Most patients present
with localized disease and are treated with curative intent; however a subset of patients develop
metastatic disease. Once metastatic, treatment is palliative, and disease behavior is variable in so
far as some patients have asymptomatic, indolent disease for years before growing rapidly and
necessitating treatment. Results of historical trials in metastatic SGC are difficult to interpret
given inclusion of patient with indolent disease. As such, contemporary studies have limited
enrollment to patients with documented progressive disease2. Although often grouped together
due to their rarity and anatomic location, malignant metastatic SGC encompass several distinct
tumors of which the most common is adenoid cystic carcinoma (ACC)3.

There are no approved systemic therapeuties for ACC. Cytotoxic chemotherapies and
combinations have shown overall response rate (ORR) ranging 0-44% (albeit with unclear
survival benefit)4, and multi-receptor vascular endothelilal growth receptor (VEGFR) tyrosine
kinase inhibitors which have shown response rates ranging from 0-15% and a median
progression free survival (PFS) of 5.7-17.5 months (mo)5–10. In a randomized trial, axitinib
demonstrated an improvement in mPFS (5.7 vs 2.8 mo) versus observation with an ORR of only
9%5.

Other non-ACC salivary gland cancers include salivary ductal carcinoma, acinic cell
carcinoma, mucoepidermoid carcinoma, and mammaPry analog secretory carcinoma. Although
some of these tumors may have targetable molecula r alterations including androgen receptor
overexpression, HER2 amplification and/or overexpression, or rarely actionable genomic
alterations (i.e. NTRK fusions), treatment options are limited with no approved systemic agents.
Recognizing that a survival benefit is seeEn despite a lack of overt radiographic response,
contemporary studies have pivoted toL use of PFS as the primary efficacy endpoint for trials in
SGC especially ACC2.

Mutations in the TP53 gene are the most common molecular alteration in solid tumors
but TP53 is frequently unalteTred in SGC. The p53 protein is a potent transcription factor that
plays a prominent role in Rmany human malignancies. In cells containing wild- type p53, MDM2
is the cellular protein responsible for the negative regulation of p53 transactivation via an
autoregulatory feedback mechanism. When activated, p53 transcribes the MDM2 gene leading to
production of the MDM2 protein. MDM2 proceeds to directly bind to p53 which inhibits the
function of p53 via several mechanisms11,12. MDM2 gene amplifications are a common event in
SGCs, particularly prevalent in ACC13–15. MDM2 inhibition has been of particular interest in
SGC as a mechanism to restore p53 function. MI-773 previously was shown to mediate ACC
tumor regression in patient-derived xenograft models of ACC as both a single agent as well as
potential synergy when administered in combination with platinum chemotherapy16,17.
Alrizomadlin is a potent oral small-molecule MDM2 inhibitor which shows significant cell
growth inhibitory activity in vitro at low nanomolar concentrations and was previously evaluated
in a first in human clinical trial in advanced solid tumors. Given these data, we hypothesized
that alrizomadlin would have significant clinical activity in TP53 wildtype (TP53wt) SGC.

In this work, we conducted a phase I clinical trial to evaluate the safety and anti tumor
activity of alrizomadlin +/- carboplatin in patients with progressive TP53wt SGC.

Results
Patient and Disease Characteristics
Forty-one patients were enrolled between October 2019 and February 2024. Forty
patients received at least one dose of drug and were evaluable for DLT (Figure 1). Baseline
characteristics for 40 enrolled patients evaluable for toxicity are shown in (Table 1). Median age
was 59 years (range: 33-76), 26 patients were female (65%), and the majority had ACC (n=31,
78%). Fourteen patients (35%) had previous palliative systemic therapy for locoregionally
recurrent or metastatic salivary gland cancer, of which six patients had previous VEGFR TKI
exposure. The median number of prior lines of therapy was 2 (range 1-7). All patients had PD
by imaging at baseline, with one patient having new metastatic disease. All other patients had >
20% increase in tumor burden within 12 months of enrollment (median: 55.8%, range: 21.7% to
300%). Of the 27 patients who had scans available in the previous 6 months, 25 patients (93%)
had a > 20% increase.

Dose Finding and Dose Limiting Toxicities
During the study, among the 40 patients evaluable for toxicity, four patients experienced
DLTs (three in the monotherapy arm, one in the combination arm). Amongst patients in the
monotherapy arm, DLTs included two cases of grade 4 neutropenia and one instance of
grade 3 dizziness. Among these three patients, one DLT occurred during cycle 1 and two
occurred during cycle 2. In the combination arm, one patient experienced neutropenic fever
(grade 3) with associated anemia (grade 3) and neutropenia (grades 4) during cycle 1. For all
cases, DLTs resolved and patients were able to resume treatment at a reduced dose.

Dose de-escalation was not recommended by the TITE-CRM for alrizomadlin
monotherapy and all patients were treated at the highest dose level (150 mg). The number of
observed DLTs and the estimated posterior probability of toxicity at the three dose levels are
shown in Supp Table 1. The dose level of alrizomadlPin monotherapy closest to the target
probability of 30% was 150 mg, which was determ ined to be the MTD.

Alrizomadlin Monotherapy
Toxicity, Dose Reductions, and Reasons for Discontinuation
Treatment with alrizomadlin monothEerapy was tolerated relatively well with 3 patients
(9.1%) discontinuing due to treatmentL related AEs (TRAEs). Seventeen (52%) patients came off
therapy due to progression, 4 (12%C) due to physician discretion, and 4 (12%) due to patient
withdrawal of consent. A total of 17 patients (52%, 13 monotherapy, 4 combination) required at
least one dose modification. TTen patients underwent one dose reduction to 100 mg (all
monotherapy), and 3 patieRnts underwent two dose reductions to 50mg. The most common grade
3 TRAEs included fatigue (22%), thrombocytopenia (19%), neutropenia (17%), and nausea
(11%) (Table 2). Grade 4 myelosuppression (neutropenia and thrombocytopenia) was observed
in four patients (11%).

Efficacy
Thirty-four response-evaluable patients were treated with alrizomadlin monotherapy. Among
the first stage of 14 patients treated with alrizomadlin monotherapy (Arm A), there were 2
responses thereby allowing for enrollment to the second stage. Five patients (14.7%) had a
confirmed partial response (PR), and 27 had a best response of stable disease (SD) (79.4%),
amounting to a disease control rate (DCR) of 94.1% (Table 3). Two patients (5.9%) had a best
response of progressive disease (PD). The median follow-up time for PFS was 15.0 months. The
6-month progression free survival (PFS) was 69.8% (95% CI: 55.7, 87.3) with a median PFS of
9.3 months (95% CI: 7.4, 14.0). The median duration of therapy was 7.8 months (range 1.3-31.5)
and as of 5/08/25, 3 patients were still on active therapy as of the data cut off as shown in the
swimmer's plot (Figure 2). Twenty-six patients (76.5%) showed reductions in tumor sizes during
follow-up as shown in Figure 3.

A planned analysis of the efficacy of alrizomadlin monotherapy in patients with ACC (n=25)
versus non-ACC (n=9) was undertaken to best identify populations deriving benefit from
therapy. Among patients with ACC, five (20.0%) had a confirmed PR and 19 had a best response
of SD (76.0%) amounting to a DCR of 96.0%. The 6-month PFS was 75.0% (95% CI: 59.5,
94.5) with a median PFS of 9.7 months (95% CI: 8.1, 18.6) (Figure 4). In non-ACC patients, no
patients had a confirmed PR and 8 had a best response of SD (88.9%). The 6-month PFS was
55.6% (95% CI: 31.0, 99.7) with a median PFS of 7.4 months (95% CI: 4.6, not evaluable (NE)).
There was no statistically significant difference in PFS between the two groups (log-rank
p=0.69); however, small group sizes limit the power to detect between-group differences.

Alrizomadlin + Carboplatin
Four patients were enrolled to alrizomadlin + carboplatin (Arm B) prior to closure of the
combination arm, all of whom had ACC (Supp Table 2). One patient had a confirmed PR and
the other three had a best response of SD. The 6-month PFS was 75% (95% CI: 43, 100) with a
median PFS of 19.8 months (95% CI: 4.8, NE) (Supp Figures 1, 2). Among patients treated with
the combination of alrizomadlin and carboplatin there was a higher rate of grade 3 and 4 TRAEs
(Supp Table 3). Grade 4 TRAEs included neutropenia (n=2) as well as thrombocytopenia (n=1)
and the most common grade 3 TRAEs included thrombocytopenia (n=3), neutropenia (n=2), and
anemia (n=2). Four patients underwent two dose reductions to 50 mg.

Translational Studies
Targeted genomic sequencing of 18 salivary gland tumors, comprising 14 ACC and 4
non-ACC tumors, revealed a low frequency of somatic mutations (Figure 5). In the ACC group,
each of these genes PTEN, NTRK1, MET, BRCA2, FGFR4 harbored a missense mutation in a
single tumor (1/14; 7.1%), and a nonsense mutation was identified in SETD2, also in one ACC
tumor (1/14, 7.1%). In the non-ACC group, a single mPissense mutation was detected in MTOR
in one of four tumors (1/4, 25%). Importantly, no m utations were identified in TP53 in either
ACC or non-ACC tumors, confirming that all samples were TP53wt. In addition, no mutations
were detected in MDM2 or MDM4 in any tumor.

Exploratory analysis in patients wEith adenoid cystic carcinoma showed no difference in
MYB staining based on clinical benefLit (defined as SD or PR for > 6 months) (Figure 6). The
association between ALDH1A1 anCd PFS was positive (R=0.255) but not statistically significant
(p=0.278).

Methods
Study Design and Patients
The study (NCT03781986) was approved by the institutional review board at UMCC as
well as participating sites and conducted in accordance with the Declaration of Helsinki and
Good Clinical Practice Guidelines. This was an open label, multicenter phase I trial conducted at
the University of Michigan Rogel Cancer Center (UMCC, Ann Arbor, MI), H. Lee Moffitt
Cancer Center (Tampa, Florida), and University of Chicago Cancer Center (Chicago, Illinois).
All patients provided written informed consent before enrollmentS. Patients with histologically
documented malignant salivary gland cancers non amenable to curative therapy were eligible if
they met the following criteria; previous mutational testing demonstrating no evidence of a TP53
mutation; presence of measurable disease by Response Evaluation Criteria in Solid Tumors
(RECIST) version 1.1; >20% increase in tumor burden in the preceding 12 months per RECIST
by treated physician assessment; Eastern Cooperative Oncology Group performance status 0 or
1; age > 18 years old; able to take oral medications without breaking capsules; and adequate
organ and bone marrow function. Any number of prior therapies were allowed. Exclusion
criteria included prior treatment with an MDM-2 inhibitor, active brain metastases, or
progressive disease within 6 months of tEhe last dose of platinum based chemotherapy. Complete
eligibility criteria can be found in the Lstudy protocol (online only). Participants were not
compensated for participation. PaCtient sex was collected and based on self-reporting, gender was
not collected. The cutoff date foIr analysis was May 8, 2025.

Study Procedures
Doses were assignRed using the time-to-event continual reassessment method (TITE-
CRM), which continuoAusly estimates the probability of dose-limiting toxicity (DLT) and assigns
patients to the dose closest to but not exceeding the estimated target rate of 30% using a one-
parameter logistic regression and Bayesian modeling18,19. The acute observation period for DLT
comprimised the first two cycles of treatment, constituting a 42-day time period. The initial dose
level for alrizomadlin was 150mg which could be decreased to 100 or 50mg.

Alrizomadlin was administered orally every other day, days 1-14 in 21 day cycles.
Starting dose level was recommended by Ascentage Pharma based on safety, tolerability, and
pharmacokinetics from a previously completed first in human study (NCT02935907)20. Dose
adherence was monitored by pill diaries. In patients treated with both carboplatin and
alrizomadlin, carboplatin was also administered on day 1, with starting dose level utilizing a area
under the curve dose of 4.5 and alrizomadlin 150 mg (Supp Table 2). Treatment was continued
until disease progression, intercurrent illness precluding further treatment, unacceptable adverse
events (AEs), death, withdrawal of consent, or at the treating physician’s discretion. Imaging
was obtained once every 6 weeks for the first six cycles, then extended to every 9 weeks.

Dose-Limiting Toxicity
Non-hematologic DLTs were defined as ≥ grade 3 non-hematological AEs, excluding
nausea, vomiting, diarrhea; ≥ grade 3 nausea, vomiting, or diarrhea uncontrolled by maximal
antiemetic/ antidiarrheal therapy; any AE which in the judgment of the investigator was
considered a DLT; grade 3 ALT and/or AST elevation. Hematologic DLTs were defined as
thrombocytopenia of ≥ grade 3 if associated with clinically significant bleeding; ≥ grade 3
anemia lasting ≥ 7 days; grade 4 thrombocytopenia lasting ≥ 7 days; grade 4 neutropenia lasting
7 days or more; ≥ grade 3 neutropenia with a temperature of at least 38.5°C; or ≥ grade 3
neutropenia with ≥ grade 3 infection.

Biomarker Analysis
Immunohistochemistry
Immunohistochemistry (IHC) for MYB was performed using pS11-MYB (clone
#EP769Y). MYB scoring was conducted by a board certified head and neck pathologist (JBM)
who determined the percentage of positive tumor nuclei.

ALDH1A1 staining was performed as previously described21, with the addition of 0.1%
Tween 20 in the wash buffer. Briefly, slides were deparaffinized, rehydrated and boiled at 950C
in citrate buffer for 20 minutes. Sections were permabilized with Triton X-100, 3% hydrogen
peroxides, blocked with avidin/biotin (Vector Laboratories) and background sniper (Biocare
Medical). ALDH1A1 (1:1000), 40C, O/N was detected using Mach3 probe and Mach 3M-
polymer-HRP, and stained with Betazoid DAB Chromagen kit (Biocare Medical). Slides were
counterstained with Hematoxylin (Vector Laboratories). ALDH1A1 quantification was
performed by a board-certified oral and maxillofacial pathologist (FN) using I-score values,
which combine staining intensity and percentage of positivity, were obtained using Aperio
ImageScope (Leica Biosystems). This was followed by a descriptive analysis of staining
localization in tumor cells versus stroma, and cytoplaPsm versus cell membrane.

The correlation between ALDH1A1 stainin g quantification and PFS was assessed. The
correlation coefficient was calculated for all individuals with available tissue who completed
treatment at the time of analysis. Analysis was performed using R v4.3.1.

DNA Sequencing
DNA extraction from formalin fixed, Lparaffin embedded (FFPE) specimens was conducted as
previously detailed22,23. A board- cCertified head and neck pathologist (J.B.M.) identified the
tumor areas. Both tumor and adjacent normal tissue cores were collected, and genomic DNA was
extracted using the Qiagen ATllprep DNA/RNA FFPE kit (Qiagen, Hilden, Germany). The DNA
was quantified with a QubRit, following the methodology previously described22. Subsequently,
the DNA samples were sent to the University of Michigan Advanced Genomics core for library
preparation and sequencing.

Targeted capture sequencing library and analysis: A minimum of 100 ng of genomic DNA from
both tumor and adjacent normal tissue isolations was utilized for library preparation using the
Rubicon DNA Thruplex (Rubicon Genomics, Ann Arbor, MI, USA) following the
manufacturer’s instructions. Targeted capture was subsequently performed with our Nextera
custom capture library, which includes 7814 high-density probes covering the coding exons of
233 genes. Next generation sequencing was carried out on an Illumina NovaSeqXPlus (Illumina,
San Diego, CA, USA) using the paired-end 151-bp reads.

Quality Control, Variant Calling and Copy Number Analysis: Raw sequencing reads
were first accessed for quality using FastQC (v0.11.9). Trimming of low-quality bases and
adapter sequences was performed using Trimgalore (v0.6.7) with default parameters. The filtered
reads were then aligned to the human reference genome (GRCh38) using BWA-MEM (v0.7.17).
Alignment files were processed with SAMtools (v1.12) to convert SAM to BAM format and sort
reads by coordinate. Duplicate reads were identified and marked using picard-tools (v3.0.0).
After marking duplicates, GATK (v4.3.0.0) was used for BQSR following best practices. The
BaseRecalibrator tool was applied using known variant databases (dbSNP, 1000 Genomes, and
Mills indels), followed by application of recalibrated scores with ApplyBQSR. Variants were
identified using VarScan2 (v2.4.6) in somatic mode. The resulting variant call format file was
annotated using ANNOVAR (v9.2019) to map functional annotations, including gene
information, variant consequences, population allele frequencies et al. This was followed by
filtering the variants in the introns and intergenic regions. Variants with a minimum of five reads
supporting the alternate allele in the tumor samples were considered as potential positives. Next,
Copy number alterations were estimated using CNVkit (v0.9.12). CNVkit was run in batch mode
using the pooled normal samples as a reference to calculate log2 copy number ratios for each
tumor sample. Mutation and clinical data visualization, including oncoplots, was performed
using maftools (v2.18.0) in R.

Statistics & Reproducibility
The co-primary endpoints were determination of the DLT/maximally tolerated dose
(MTD) as well as ORR per RECIST 1.1 for alrizomadlin monotherapy +/- carboplatin. Planned
protocol specified secondary endpoints included safety via CTCAE v 5.0, survival endpoints
(overall survival, PFS, duration of response (DOR)), and ORR by tumor histology (ACC vs. non-
ACC). Evaluation of survival endpoints based on histologic subtype (ACC vs non-ACC) was
performed as a non protocol specified exploratory analysis. The study was initially designed to
enroll 62 response-evaluable patients in two phases (42 in the first phase (14 in Arm A-
alrizomadlin monotherapy, 28 in Arm B- alrizomadlin + carboplatin), then an additional 20 in
the arm with the best response rate). After 4 patients were enrolled in Arm B, the trial design was
modified to a single arm study of alrizomadlin monotherapy after safety meetings noted
increased toxicities in the combination arm. The reviPsed sample size was 34 response-evaluable
patients in Arm A total (Figure 7). If less than two responses (partial or complete) were seen in
the first stage, the trial would be stopped however if two or more responses were seen in the first
14 evaluable patients treated with APG-115 monotherapy, enrollment would continue with
enrollment of the additional 20 patients. E Using a 1-sided exact test of binomial proportions and
an α= 0.05, we defined MTD as the dLose level assigned to the next patient if a new patient were
to be enrolled (i.e., the highest dosCe level for which the estimated posterior probability of toxicity
is ≤ 30%). Adverse events were summarized at the patient level using the highest grade when
multiple AEs were present foTr the same category. Overall survival was defined as the time from
start of treatment to deathR, with censoring at the last follow-up. Progression-free survival was
defined as the time from start of treatment to the earlier of progression or death, with censoring
at the time of transition to new therapy if within 8 weeks of the last imaging assement, or time of
the last imaging assessement. Time-to-event endpoints were summarized using the Kaplan-Meier
method.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "Thank you for the invitation to review this manuscript.\nThis is a phase 1 clinical trial exploring the activity of the novel MDM2 inhibitor alrizomadlin in salivary gland cancers. It is a\nwell written report with a very balanced conclusion.\nMy questions/suggestions are below:\n1. More detail on study design would be very useful. If this is not a first in human study, prior clinical experience and\ntoxicities would be good to include in the introduction as well as the rationale for use of 150mg at with alternating dosing.\n2. The figures indicate that 19 patients were randomized to arizomadlin monotherapy vs arizomadlin + carbopatin (Figure 1\nand extended data figure 1) which is not discussed or described in the methods. The extended figure and statistical section\nalso describes a first stage and second stage within the study, was the dosing of the drug 150mg at the first stage as well?\n3. With respect to the requirement for progression in 12 months prior to enrollment, was this based on treating physician\nassessment, or was there a more prescriptive requirement of 2 scans done at certain intervals and formal RECIST\ndetermination within the 12 months prior to registration?\n4. Did the investigators limit enrollment to the specific histologies described under \"Study design and patients\", if so what\nwas the rationale to not include a wider WHO classification salivary gland cancer population?\n5. Were patients with prior platinum exposure or progression on prior platinum therapy excluded?", "reviewer_2": "The authors present a early phase clinical trial testing a novel MDM2 inhibitor in salivary gland cancer. This work is a logical\nextension of preclinical work from this group (and others - see PMC5641244) demonstrating that in salivary gland tumors\nwith high rates of wild-type TP53 inhibition of MDM2 can be an effective treatment approach and may synergize with\nsystemic chemotherapy or radiation (PMC5641244). Unfortunately, toxicity rates in the combined group were high so the\nstudy ultimately is a single arm study in salivary gland cancers. The results are intriguing and the authors hypothesize that\nuse of lower dose systemic therapy could result in improved outcomes. I would encourage them to consider highly targeted\nradiation therapy which is often using in palliation of these patients and has similar preclinical data supporting combination\ntherapy.\nWith regard to this manuscript, i believe the work is novel and the conclusions and claims reasonable and supported by the\ndata. I noted no flaws in data analysis or interpretation. Other that a suggestion to discuss the opportunity to combine this\nagent with radiation i have no other significant comments.", "reviewer_3": "This phase I trial was originally designed as a randomised double blind two arm trial (n=62),\narm A alrizomadlin monotherapy (n=42) , arm B alrizomadlin + carboplatin (n=28) , additional 20 patients in arm with best response rate. Early in\nthe study (4 enrolled in arm B) enrolment in arm B was stopped due to toxicity.\nExtensive descriptive summary statistics are reported, together with Kaplan Meier curves for the outcomes, and swimmer\nplots showing individual patients’ progression, following the revised protocol. The limitations of the study have been\ndiscussed.\nAbstract\nThe abstract does not mention the number of patients in arm B that were enrolled , nor the adverse events that were reported\nin this small group.\nThe sub group comparison of the adenoid cystic carcinoma patients with non-adenoid cystic carcinoma patients, all in arm\nA, for progression free survival, is described as “appeared to have a greater benefit”. The groups have not been compared\nwith a statistical test, which should be reported together with the p-value, and a comment on whether the difference was\nstatistically significant."}, "author_response": "Point by Point Response to Reviewer Comments:\nReviewer #1 (Remarks to the Author); expert in salivary gland cancer:\nThank you for the invitation to review this manuscript.\nThis is a phase 1 clinical trial exploring the activity of the novel MDM2 inhibitor alrizomadlin\nin salivary gland cancers. It is a well written report with a very balanced conclusion.\nMy questions/suggestions are below:\n1. More detail on study design would be very useful. If this is not a first in human study,\nprior clinical experience and toxicities would be good to include in the introduction as\nwell as the rationale for use of 150mg at with alternating dosing.\nThank you for this feedback. As discussed in the study design section, this was a phase 1\nstudy with doses assigned using the time-to-event continual reassessment method (TITE-\nCRM). A phase 1 design was chosen both because chemotherapy had not previously been\nstudied in combination with alrizomadline but also it was unknown if there was going to be\na unique safety signal in this population. During trial development, we collaborated with\npartners at Ascentage Pharma to identify the ideal dose and schedule for our dose levels.\nStarting dose and dose levels selected in this study were based off the results of the FIH\nAPG115US001 study (NCT02935907). This was a phase I single-agent, open-label, dose-\nescalation, first-in-human study evaluating the safety and tolerability of orally administered\nAPG-115 in patients with advanced solid tumors in various doses and treatment schedules.\nUnfortunately, data from this study was never published in manuscript form. Based on the\nsafety data, patient tolerability, and pharmacokinetics Ascentage recommended a starting\ndose of APG-115 150 mg every other days for two weeks on, one week off.\nTo respond to your input, we have tried to provide greater clarity to this choice with edits to\nthe background and Methods sections. We have also added a citation to the 2019 ASCO\nAnnual Meeting to which data from APG115US001 was submitted.\nBackground:\n“Alrizomadlin is a potent oral small-molecule MDM2 inhibitor which shows\nsignificant cell growth inhibitory activity in vitro at low nanomolar concentrations\nand was previously evaluated in a first in human clinical trial in advanced solid\ntumors.”\nMethods:\n“Alrizomadlin was administered orally every other day, days 1-14 in 21 day cycles.\nStarting dose level was recommended by Ascentage Pharma based on safety,\ntolerability, and pharmacokinetics from a previously completed first in human study\n(NCT02935907)20.”\n2. The figures indicate that 19 patients were randomized to arizomadlin monotherapy\nvs arizomadlin + carbopatin (Figure 1 and extended data figure 1) which is not\ndiscussed or described in the methods. The extended figure and statistical section\nalso describes a first stage and second stage within the study, was the dosing of the\ndrug 150mg at the first stage as well?\nThank you for this question.\nThe study was initially designed to enroll 62 response-evaluable patients in two phases (42\nin the first phase (14 in Arm A- alrizomadlin monotherapy, 28 in Arm B- alrizomadlin +\ncarboplatin), then an additional 20 in the arm with the best response rate). After 4 patients\nwere enrolled in Arm B, the trial design was modified to a single arm study of alrizomadlin\nmonotherapy after safety meetings noted increased toxicities in the combination arm. The\nrevised sample size was 34 response-evaluable patients in Arm A total (Figure 1). If less\nthan two responses were seen in the first stage, the trial would be stopped however if two\nor more responses (PR or CR) were seen in the first 15 evaluable patients treated with APG-\n115 monotherapy, enrollment would complete with the additional 20 patients. Using a 1-\nsided exact test of binomial proportions and an α= 0.05, we defined MTD as the dose level\nassigned to the next patient if a new patient were to be enrolled (i.e., the highest dose level\nfor which the estimated posterior probability of toxicity is ≤ 30%). Doses were assigned\nduring the entirety of the study using the TITE-CRM design. Given the low rate of severe\ntoxicities during the DLT period, all patients in the monotherapy cohort were recommended\nto be assigned to the 150 mg dose level. This description is contained under the ‘Statistical\nAnalysis’ section of the Methods. The referenced figure is a flowchart which depicts the\ntrial schema including randomization, modification to single arm trial design, two stage\nresponse design, and stable dose assignment.\nWe have added additional wording regarding the criteria for 2 responses needed to proceed\nto enrollment of the second stage to the statistical methods. Hopefully this clarifies the\nstudy flow.\n“The study was initially designed to enroll 62 response-evaluable patients in two\nphases (42 in the first phase (14 in Arm A- alrizomadlin monotherapy, 28 in Arm B-\nalrizomadlin + carboplatin), then an additional 20 in the arm with the best response\nrate). After 4 patients were enrolled in Arm B, the trial design was modified to a\nsingle arm study of alrizomadlin monotherapy after safety meetings noted increased\ntoxicities in the combination arm. The revised sample size was 34 response-\nevaluable patients in Arm A total (Supplemental Figure 1). If less than two responses\n(partial or complete) were seen in the first stage, the trial would be stopped however\nif two or more responses were seen in the first 15 evaluable patients treated with\nAPG-115 monotherapy, enrollment would continue with enrollment of the additional\n20 patients.”\n3. With respect to the requirement for progression in 12 months prior to enrollment,\nwas this based on treating physician assessment, or was there a more prescriptive\nrequirement of 2 scans done at certain intervals and formal RECIST determination\nwithin the 12 months prior to registration?\nThank you for this question. The requirement of > 20% increase in tumor burden by treating\nphysician assessment within 12 months preceding registration required formal\nradiographic progression per RECIST. This is graphically illustrated in the spider plot (Fig 3,\nExtended Data Fig 4). The scans demonstrating 20% growth could have been performed at\nany interval within the preceding 12-month period. We believe these strict definitions of\nprogressive disease strengthen our manuscript by ensuring a population with actively\ngrowing disease. We have edited the Materials and Methods section as follows:\n“…non amenable to curative therapy were eligible if they met the following criteria;\nprevious mutational testing demonstrating no evidence of a TP53 mutation;\npresence of measurable disease by Response Evaluation Criteria in Solid Tumors\n(RECIST) version 1.1; >20% increase in tumor burden in the preceding 12 months\nper RECIST by treated physician assessment; Eastern Cooperative Oncology Group\nperformance status 0 or 1; age > 18 years old; able to take oral medications without\nbreaking capsules; and adequate organ and bone marrow function.”\n4. Did the investigators limit enrollment to the specific histologies described under\n\"Study design and patients\", if so what was the rationale to not include a wider WHO\nclassification salivary gland cancer population?\nThank you for this question. Per the eligibility criteria found in the protocol (Section 3.1),\npatients with “histologically documented malignant salivary gland cancers (including\nsecretory glands of the aerodigestive tract) with or without metastases, not amenable to\ncurative treatment” were eligible for participation. As such, the wide spectrum of salivary\ngland cancers under the WHO classification were eligible. Given our planned analysis of\nACC vs non-ACC, we specifically referenced this histology. To clarify the study population\nand align the protocol with the manuscript, we have edited the text as follows:\nPatients with histologically documented malignant salivary gland cancers adenoid\ncystic carcinoma, salivary ductal carcinoma, and high grade malignant salivary\ngland cancers non amenable to curative therapy were eligible….\n5. Were patients with prior platinum exposure or progression on prior platinum\ntherapy excluded?\nPatients were excluded if they had progressive disease within 6 months of the last dose of\nplatinum-based chemotherapy. This has been added to the protocol per your\nrecommendation.\nExclusion criteria included prior treatment with an MDM-2 inhibitor, active brain\nmetastases, or progressive disease within 6 months of the last dose of platinum\nbased chemotherapy\nReviewer #2 (Remarks to the Author); expert in salivary gland cancer:\nThe authors present a early phase clinical trial testing a novel MDM2 inhibitor in\nsalivary gland cancer. This work is a logical extension of preclinical work from this\ngroup (and others - see PMC5641244) demonstrating that in salivary gland tumors with\nhigh rates of wild-type TP53 inhibition of MDM2 can be an effective treatment\napproach and may synergize with systemic chemotherapy or radiation (PMC5641244).\nUnfortunately, toxicity rates in the combined group were high so the study ultimately\nis a single arm study in salivary gland cancers. The results are intriguing and the\nauthors hypothesize that use of lower dose systemic therapy could result in improved\noutcomes. I would encourage them to consider highly targeted radiation therapy\nwhich is often using in palliation of these patients and has similar preclinical data\nsupporting combination therapy.\nWith regard to this manuscript, i believe the work is novel and the conclusions and\nclaims reasonable and supported by the data. I noted no flaws in data analysis or\ninterpretation. Other that a suggestion to discuss the opportunity to combine this\nagent with radiation i have no other significant comments.\nThank you very much for your feedback. We are excited about this data and hope to\ncontinue evaluating MDM-2 inhibition in future trials.\nReviewer #3 (Remarks to the Author); expert in statistics:\nThis phase I trial was originally designed as a randomised double blind two arm trial (n=62),\narm A alrizomadlin monotherapy (n=42) , arm B alrizomadlin + carboplatin (n=28) ,\nadditional 20 patients in arm with best response rate. Early in the study (4 enrolled in arm\nB) enrolment in arm B was stopped due to toxicity.\nExtensive descriptive summary statistics are reported, together with Kaplan Meier curves\nfor the outcomes, and swimmer plots showing individual patients’ progression, following\nthe revised protocol. The limitations of the study have been discussed.\nAbstract\nThe abstract does not mention the number of patients in arm B that were enrolled, nor\nthe adverse events that were reported in this small group.\nThank you for this feedback. We acknowledge this limitation, however when reformatting\nthe abstract per journal requirements we were noted to exceed abstract limitation (290\nwords, limitation of 150 or fewer. We have consolidated the abstract to meet these\nlimitations and included reference to the enrollment and rate of adverse events in Arm B.\nWe are currently at 150 words and unfortunately have left discussion of these important\nitems to the text.\nPreclinical studies have evaluated MDM2 inhibitors as a treatment for adenoid\ncystic carcinoma (ACC), but clinical trials are lacking. This multicenter phase I trial\nassessed the safety and antitumor activity of an oral MDM2 inhibitor, alrizomadlin\n(APG-115), +/- carboplatin in TP53 wild type unresectable recurrent/metastatic\nsalivary gland cancers (R/M SGC) with a planned 1:1 randomization to carboplatin\nchemotherapy. The primary endpoint was determination of dose-limiting toxicity\n(DLT). After enrollment of 4 patients to combination therapy, the trial was modified\nto a single arm study of alrizomadlin monotherapy due to excess toxicity. 1 DLT was\nseen in the combination arm, all patients had > G3 TRAE. 37 patients were enrolled\nto alrizomadlin monotherapy. 3 DLTs were encountered, 67% of patients had > G3\nTRAE. The RR was 15% with mPFS 10.5 mo. These findings demonstrate\nencouraging tolerability of alrizomadlin monotherapy with promising antitumor\nactivity in patients with TP53 SGC, especially ACC.\nThe subgroup comparison of the adenoid cystic carcinoma patients with non-adenoid\ncystic carcinoma patients, all in arm A, for progression free survival, is described as\n“appeared to have a greater benefit”. The groups have not been compared with a\nstatistical test, which should be reported together with the p-value, and a comment on\nwhether the difference was statistically significant.\nThank you for this comment. We now report the log-rank test p-value comparing PFS\nbetween the ACC and non-ACC groups in the Results and indicate that this difference is\nnot statistically significant. Since the study was not designed to detect differences\nbetween these two groups and given the small group sizes, we have also noted that group\ncomparisons have limited power.\n“The 6-month PFS was 55.6% (95% CI: 31.0, 99.7) with a median PFS of 7.4 months\n(95% CI: 4.6, not evaluable (NE)). There was no statistically significant difference in\nPFS between the two groups (log-rank p=0.69); however, small group sizes limit the\npower to detect between-group differences.”"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The questions have been appropriately addressed.", "reviewer_2": "No additional edits", "reviewer_3": "Thank you for your response and for addressing my comments relating to the abstract and to the log-rank test comparing\nPFS between the ACC and non-ACC groups."}, "author_response": ""}]

Decision letter