A Phase I/II Combination Study of NMS-03305293 and Temozolomide in Adult Patients with Recurrent Glioblastoma

Glioblastoma is one of the most common malignant primary brain tumors in
adults. Due to its aggressive and highly proliferative course, glioblastoma is
defined a grade 4 tumor based on the World Health Organization (WHO)
classification.

Standard treatment consists of maximal safe surgical resection or a diagnostic
biopsy, followed by radiotherapy (RT) with concomitant daily temozolomide (TMZ)
chemotherapy, and then maintenance treatment with TMZ for 6 months according to
the EORTC NCIC protocol (Stupp et al.; 2005). Despite some improvements over
the years in neuro-imaging, chemotherapy, surgical and RT techniques and
chemotherapy, the prognosis for these patients remains poor, with a median OS
of 14.6 months, an OS rate of 27% at 2 years, and only about 10% surviving at 5
years. Glioblastoma is considered a chemo and radio-resistant tumor, in fact
recurrence occurs in more than 90% of patients, mostly in the irradiation field
and, even in tumors with O6-methylguanine DNA methyltransferase (MGMT) promoter
methylation, the response to chemotherapy is temporary. At recurrence, there is
no standard of care available. Surgery or reirradiation can be offered to
patients with circumscribed recurrences. Most patients with recurrent
glioblastoma who are eligible for salvage therapy are treated with a second
course of alkylating agent chemotherapy, e.g. re-treatment with TMZ, especially
after a long time to recurrence after initial therapy with adjuvant TMZ, or
mostly lomustine (CCNU). Bevacizumab as a single agent was approved in the USA,
although not in the European Union, based on prolonged progression- free
survival, but no survival benefit was ever proven. Bevacizumab, where
available, is commonly used in symptomatic patients at later recurrences. In
the absence of effective therapies for recurrent glioblastoma, participation of
subjects in clinical trials is encouraged.

In the effort to identify effective therapies for patients with glioblastoma,
an attractive approach is the enhancement of the antitumor activity of
irradiation or alkylating therapies (e.g. TMZ, RT) by impairing DNA repair.
PARP-1 is known to have an important function in DNA repair and PARP inhibition
has been considered as a novel approach to target tumors with deficiencies in
DNA repair mechanisms and to enhance the DNA damaging effect of chemotherapy
and ionizing radiation.

Gliomas are highly infiltrative with tumor cells extending beyond regions of
contrast enhancement in essentially all tumors; thus, brain distribution of
drugs used to treat glioblastoma is critically important to target all tumor
cells within the brain. Poor penetration of the blood brain barrier (BBB)
undermines the efficacy of many pharmaceutical agents in CNS tumors, including
PARPi, tested for the treatment of glioblastoma.

Several studies have been launched to assess the safety and efficacy of various
PARPi in patients with glioblastoma, but no proven benefit has been
demonstrated yet possibly due to low brain penetration and/or low potency
(veliparib) or to the increased hematological toxicity likely linked to the low
selectivity on PARP-1 and to the ability of trapping the PARP proteins on DNA,
thus interfering with DNA replication and ultimately causing cell death of
highly proliferating cells (olaparib, niraparib, rucaparib and talazoparib).

NMS-03305293 is a member of the isoindolinone chemical class and is a potent
inhibitor of PARP-1 (KD=2.72 nM). NMS-03305293 has high selectivity for PARP-1
vs the other enzymes of the PARP family, including PARP-2 (KD=691 nM). The
compound exhibited potent anti-proliferative activity against BRCA mutated or
homologous recombination deficient (HRD) tumor cell lines, with IC50 in the low
nanomolar range.
Specificity was confirmed using a panel of DNA repair proficient cell lines,
against which the compound was essentially inactive.

When NMS-03305293 was combined with TMZ in glioblastoma models, either
sensitive or resistant to TMZ treatment, good tolerability and more than
additive antitumor activity were observed.

NMS-03305293 was tested in combination with TMZ against three glioblastoma
models: T98-G, BT-308 and intracranially implanted U-87 MG showing remarkable
and reproducible activity and ability to restore sensitivity to TMZ in resitant
models.

Pivotal GLP toxicity studies were conducted in rats and dogs with NMS-03305293
administered orally for 4 weeks followed by a 2- or 4- week recovery period,
respectively. Noteworthy findings in these pivotal GLP repeated dose toxicity
studies included effects on the hemolymphopoietic system in rats and dogs,
CNS-related clinical signs and changes in the brain in dogs, and effects on
testes and liver in rats. Effects on the hemolymphopoietic system included
slight to moderate dose-related hematological changes and alterations in bone
marrow and thymus with a complete recovery of bone marrow and thymus changes at
the end of the recovery period. CNS clinical signs, characterized by
aggressiveness, fear reaction, hunched posture, abnormal posture/gait, and
tremors were observed soon after dosing in dogs from the intermediate dose (20
mg/kg/day) and convulsions were observed in two females treated at the highest
dose tested (30 mg/kg/day). These signs generally started 15-30 minutes
post-dose and resolved within about one hour after onset. CNS effects were
associated with minimal to slight inflammatory infiltrates in the meninges and
no specific neuronal cell degeneration was detected. A complete recovery of
brain changes occurred after 4 weeks of drug withdrawal. Germ cell depletion in
the testes and liver findings not associated with any serum chemistry
abnormality were detected in rats from 25 mg/kg/day with partial recovery at
the end of the 2-week observation period.

In the GLP 4-week studies in rats and dogs, the terminal half-life of the
compound was short (6-11 hours in rats and 6-7 hours in dogs). No accumulation
in dogs or weak accumulation in rats was observed in the GLP 4- week studies.
Overall, no deviation from dose proportionality and time linearity was seen in
the PK studies.

NMS-03305293 has been proven to distribute extensively into brain tissue of
mice, rats and dogs. Two studies performed in mice and rats demonstrated that
brain concentrations of NMS-03305293 were four to twenty times higher than
those in plasma after a single oral administration at the dose of 10 mg/kg and
concentrations declined in parallel. In an additional study conducted in dogs,
treated with NMS-03305293 given orally at the daily dose of 20 mg/kg for seven
days, NMS-03305293 was detectable up to 48 hours post-dosing in the brain and
the systemic exposure in brain was about 6-fold higher than in plasma.

A Phase I, dose-escalation study with NMS-03305293 (PARPA-293-001) administered
as single agent daily for 21 or 28 consecutive days in 4 week-cycles is ongoing
in patients with selected solid tumors (cancer of the ovary, breast, prostate
and pancreas). The starting dose in this study was 20 mg/day. The PARPA-293-001
study is closely monitored and safety results from completed cohorts are made
available to inform investigators participating to the PARPA-293-002 study.

In conclusion, PARP inhibitors are hypothesized to enhance the efficacy of
alkylating therapies such as TMZ by impairing DNA repair. The results of the
preclinical studies demonstrate that the combination of NMS- 03305293 with TMZ
is effective both in TMZ-sensitive and TMZ-resistant models with good
tolerability. In addition, the toxicology studies conducted with NMS-03305293
as single agent demonstrate an adequate safety profile and safety margin to
support the proposed clinical trial in combination with TMZ. NMS-03305293, due
to its PARP-1 selectivity and lack of trapping activity, is expected to be well
tolerated in combination with myelotoxic agents. In addition,

This study has been transitioned to CTIS with ID 2023-508318-41-00 check the CTIS register for the current data.

Primary Objective:
• To determine the Maximum Tolerated Dose (MTD) and the Recommended Phase 2
Dose (RP2D) of NMS-03305293 in combination with temozolomide (TMZ) in patients
with diffuse gliomas at first relapse (Phase I)
• To assess the antitumor efficacy of the combination of NMS-03305293 and TMZ
in patients with Isocitrate dehydrogenase (IDH) wild type glioblastoma (Phase
II) at first relapse

Secondary Objectives:
• To characterize the safety profile of NMS-03305293 in combination with TMZ
• To evaluate the pharmacokinetics of NMS-03305293 in combination with TMZ
• To evaluate additional measures of antitumor efficacy of NMS-03305293 in
combination with TMZ

Exploratory Objectives:
• To explore the role of MGMT promoter methylation status for antitumor
efficacy of the combination
• To explore the relationship between NMS-03305293 and possible identified
metabolites (if appropriate) plasma concentrations and relevant ECG parameters

This is a multicenter, Phase I/II study on the safety and efficacy of the
combination of NMS-03305293 and temozolomide (TMZ) in adult patients with
diffuse gliomas (Phase I) and glioblastoma (Phase II) at the first relapse.

The Phase I portion of the study is designed as a single-arm, dose-escalation
study aimed at defining the Maximum Tolerated Dose (MTD) and the Recommended
Phase 2 Dose (RP2D) of NMS-03305293 in combination with TMZ and the safety
profile and tolerability of the combination therapy in patients with diffuse
gliomas.

The dose escalation part is designed with a conventional scheme of sequential
cohorts of 3 to 6 patients allocated to progressively higher dose levels of
NMS-03305293 in combination with a fixed dose of TMZ (150 mg/m2), based on the
occurrence of first-cycle DLTs up to the MTD.

All patients enrolled before the finalization of protocol v.2 received TMZ and
NMS-03305293 administered orally once daily (TMZ days 1-5; NMS-03305293 days
1-7) in repeated 4-week cycles. Based on NMS- 03305293 safety and preliminary
PK data in humans obtained in this study and in the ongoing first in human
(FIH) study (PARPA-293-001), the administration of NMS-03305293 may be explored
also as twice daily dosing (BID), starting either at the total daily dose <= 33%
increase of the highest QD dose level deemed safe, or at an intermediate total
daily dose between the previous QD dose level that has been deemed safe and the
QD dose level with unacceptable toxicity (if applicable), or a lower dose as
determined by the Sponsor and Investigators.

Through a protocol amendment, the Sponsor has the option to explore additional
schedules (e.g. TMZ days 1-5; NMS-03305293 days 1-12 in repeated 4-week cycles)
based on emerging data, starting at the same total daily dose or a lower dose
already explored and deemed safe as determined by the Sponsor and Investigators.

After the completion of each cohort, available safety and PK data will be
reviewed and the next dose level will be decided jointly by the Investigators
and the Sponsor. During the dose escalation phase, few additional patients (up
to 3-6) may be enrolled in one or more dose levels, completed and declared safe
(i.e. 0 DLT out of 3 or <=1 out of 6 patients), to further explore the safety
profile of NMS-03305293 in combination with TMZ before the Phase II starts.
Such patients will not be evaluated by DLT criteria. Patients must fulfill the
eligibility criteria and the schedule of the events for the Phase I.

Once the safety has been reviewed by the Investigators and the Sponsor and is
considered adequate based on the entire Phase I data available, the RP2D of
NMS-03305293 in combination with TMZ at 150 mg/m2 will be defined. At this
point, the Phase II part of the study will start. The Phase II portion is
designed as an exploratory study with an interim analysis for futility to
assess the antitumor activity of the study treatment measured as objective
response rate by central retrospective assessment in adult patients with IDH
wild type recurrent glioblastoma at first relapse after initial standard
therapy including up to 6 cycles of temozolomide and provided that patients
completed standard of care concurrent temozolomide and the radiation therapy.

Treatment:

Dosing schedule
All patients will receive oral treatment with NMS-03305293 administered once
(QD) or twice (BID) daily on Days 1 to 7 and with TMZ administered daily on
Days 1 to 5 in repeated 4-week cycles.
Additional schedules may be explored (e.g. TMZ days 1-5; NMS-03305293 days 1-12
in repeated 4-week cycles) through a protocol amendment.

NMS-03305293
NMS-03305293 is formulated as 10 and 50 mg capsules and administered as
out-patient treatment.
For specific formulation and storage instructions, please refer to the product
Investigator*s Brochure and the Investigational Medicinal Product Study Manual,
respectively.
The proposed starting dose of NMS-03305293 was 20 mg/day flat dose (<15
mg/m2/day).
The starting dose corresponds to 1/10 the dose in mg/m2 that in rats produced
testicular toxicity in all males (25 mg/kg/day = 150 mg/m2/day) and is the same
used for the ongoing study PARPA-293-001, in which NMS- 03305293 was
administered as single agent, daily for 21 consecutive days in 4-week repeated
cycles. No DLTs and good tolerability were observed at this dose level in
PARPA-293-001 study.

Temozolomide
TMZ is supplied as oral capsules and administered as out-patient treatment. The
proposed dose of TMZ is 150 mg/m2 per day.

Duration of treatment
All patients may continue study treatment until disease progression,
unacceptable toxicity, investigator decision, withdrawal of consent by the
patient or other discontinuation criteria described in the protocol are met.

Phase I Dose Escalation
NMS-03305293 has been administered in sequential cohorts of patients at the
following dose levels: 20 mg/day, 40 mg/day, 60 mg/day and 80 mg/day.

Based on NMS-03305293 safety and preliminary PK data in humans obtained in this
study and in the ongoing first-in-human (FIH) study PARPA-293-001, the
administration of NMS-03305293 may be explored also as twice daily dosing
(BID), starting either at the total daily dose <= 33% increase of the highest QD
dose level deemed safe, or at an intermediate total daily dose between the
previous QD dose level that has been deemed safe and the QD dose level with
unacceptable toxicity (if applicable), or a lower dose as determined by the
Sponsor and Investigators. The dose escalation will proceed with <=33%
increments of the total daily dose in QD and/or BID dosing (rounded to the
lower or higher 10 mg strength capsules available) until the MTD and/or a lower
dose above the expected efficacious threshold are reached. At each dose level,
a minimum of 3 patients will be included.

If 0/3 patients experience first cycle DLT, the next cohort will start one dose
level higher.
If 1/3 patients experience first cycle DLT, up to three more patients will
receive the study medication at the same dose level; if 1/6 experiences first
cycle DLT the next cohort will start one dose level higher.

If >=2/3 or >=2/6 patients experience DLTs in the first cycle of treatment, the
MTD is considered to have been exceeded. At this point, the Sponsor and
Investigators may request to evaluate three more patients at the previous dose
level (if only 3 patients were treated at that prior dose), or to explore an
intermediate dose level (not yet tested), in order to more precisely define the
MTD. Evaluation of safety profile and exposure in patients treated in the study
will guide the selection of the intermediate dose level.

During the dose escalation phase, in order to optimize the dose to be selected
for further clinical development, few additional patients (up to 3-6) may be
enrolled in one or more dose levels, completed and declared safe (i.e. 0 DLT
out of 3 or <=1 out of 6 patient) to further explore the safety profile of
NMS-03305293 in combination with TMZ before the Phase II starts. Such patients
will not be evaluated by DLT criteria. Patients must fulfill the eligibility
criteria and the schedule of the events for the Phase I.

The dose level will be assigned by the Sponsor at the time of patient
registration.

Only one dose level will be open for enrollment at any time in each dosing
schedule. Upon the implementation of protocol v 2.0, three patients for each
dose level can enter simultaneously.IIn case a cohort needs to be expanded to
more than 3 patients, the additional patients can be enrolled simultaneously,
after the first three patients have completed the DLT period.

All patients must be observed for one cycle before subsequent patients are
enrolled at the next higher dose level. If a patient fails to receive at least
75% of both NMS-03305293 and TMZ during the first cycle of treatment, for
reasons other than treatment-related toxicities or is not assessed for DLTs, an
additional patient must be enrolled at the same dose level. A patient may also
be replaced if, under particular circumstances (e.g. due to noncompliance), the
assessment of DLTs is not possible as judged jointly by the Investigators and
the Sponsor.

After the completion of each cohort, available safety and PK data will be
reviewed and the next dose level will be decided jointly by the Investigators
and the Sponsor.

Definition of DLT(s): DLT will be defined as any of the following adverse
events occurring in cycle 1 for which the relationship with the combination
therapy cannot be definitely excluded (see protocol).

The DLT observation window is defined as the time interval between the date of
the first dose administration in Cycle 1 and the date of the first dose
administration in Cycle 2 which is expected to be 28 days, or up to 42 days in
case of dose delay due to drug related toxicity. For patients who do not
receive Cycle 2 treatment, 42 days will be the maximum time interval considered
for the evaluation of DLT unless no drug-related toxicities are observed, or
recovery of toxicities or start of a new anticancer therapy occurs earlier.

Definition of MTD:
The MTD is defined as the highest dose level associated with the cohort at
which < 33% of patients experience a first cycle DLT.
The cohort of diffuse glioma patients with the dose of NMS-03305293 identified
as the MTD in combination with TMZ at 150 mg/m2 in the dose escalation and/or a
lower dose above the expected efficacious threshold in QD and/or BID dosing
schedule may be expanded.

Definition of RP2D:
The Recommended Phase 2 Dose (RP2D) is a dose above the expected efficacious
threshold confirmed to be well tolerated in repeated cycles with the highest
benefit/risk ratio based on available data. The RP2D will be determined at a
dose below or equal to the MTD, if characterized, upon review of all study data
by the Sponsor and Investigators.

NMS-03305293 is at an early stage of development with very limited safety data
and no efficacy results in humans available so far. Based on preclinical models
NMS-03305293 has demonstrated antitumor activity in glioblastoma along with
good tolerability. The first-in-human PARPA-293-001 study exploring the safety
and tolerability of NMS-03305293 administered as single agent daily for 21 or
28 consecutive days in 4 week-cycles is ongoing in patients with selected solid
tumors (cancer of the ovary, breast, prostate and pancreas). As of 31st of
January 2023, the dose escalation part of the study is ongoing and the current
dose level tested is 200mg/day.