Intratumoral Tavo and Pembro in Patients With Inoperable Locally Advanced or Metastatic TNBC (KEYNOTE-890)

The study will be comprised of a screening period, treatment period and a long-term
follow-up.

Eligible subjects will be treated with intratumoral tavo-EP to the accessible lesions on Days
1, 5 and 8 every 6 weeks and with IV pembrolizumab (200 mg) on Day 1 of each 3-week cycle for
up to 17 cycles of tavo-EP and 33 cycles of pembrolizumab from baseline (approximately 2
years) or until subsequent disease progression. As many accessible lesions may be treated, as
deemed feasible by the treating physician assuming the size of each lesion is greater than
0.3 cm x 0.3 cm.

Long-term Follow-up: All subjects will be followed after End of Study (EOS) visit for Serious
Adverse Events (through 90 days from last dose of study drug) and long term survival status.
EOS visit will occur 4 weeks after last study treatment administration

Inclusion Criteria:

1. Subjects with histologically confirmed diagnosis of inoperable locally advanced or
metastatic TNBC and at least 1 prior line of systemic chemotherapy or immunotherapy
that includes an approved regimen.

2. Subjects must have estrogen (ER) receptor and progesterone (PR) receptor staining <10%
and be human epidermal growth factor receptor 2 (HER2) -negative defined as
immunohistochemistry (IHC) 0 to 1+

3. Subjects must not have disease that, in the opinion of the Investigator, is considered
amenable to potentially curative treatment.

4. Age ≥ 18 years of age of day of signing informed consent.

5. Eastern Cooperative Oncology Group (ECOG) performance status 0-1.

6. Life expectancy of at least 6 months.

7. Have measurable disease based on RECIST v1.1, and at least one anatomically distinct
lesion involving skin or subcutaneous tissue accessible for electroporation of ≥ 0.3
cm and lesion must be accurately measured in at least one dimension (longest diameter
in the plane of measurement is to be recorded).

8. Demonstrate adequate organ function as defined below. All screening laboratories
should be performed within 10 days of treatment initiation.

9. For women of childbearing potential, negative serum or urine pregnancy test within 72
hours prior to the first study drug administration. If the urine test is positive or
cannot be confirmed as negative, a serum pregnancy test will be required.

10. For women of childbearing potential, must be willing to use an adequate method of
contraception from 30 days prior to the first study drug administration and 120 days
following last day study drug administration (either tavo or pembrolizumab).
Acceptable methods include hormonal contraception (oral contraceptives - as long as on
stable dose, patch, implant, and injection), intrauterine devices, or double barrier
methods (e.g. vaginal diaphragm/ vaginal sponge plus condom, or condom plus
spermicidal jelly, if available), sexual abstinence or a vasectomized partner. Women
may be surgically sterile or at least 1-year post-last menstrual period.

11. Male subjects must be surgically sterile or must agree to use contraception during the
study and at least 120 days following the last day of study drug administration.

12. Able and willing to give informed consent and to follow study instructions.

Exclusion Criteria:

1. Subject has a known additional malignancy that is progressing or requires active
treatment.

2. Clinically active CNS metastases. Subjects with previously treated brain metastases
may participate provided they are radiologically stable, i.e., without evidence of
progression for at least 4 weeks by repeat imaging (note that the repeat imaging
should be performed during study screening), clinically stable and without requirement
of steroid treatment for at least 14 days prior to first dose of study drug.

3. Subject who had an allogenic tissue/solid organ transplant

4. Subjects with electronic pacemakers or defibrillators.

5. Subject who have a known history of Human Immunodeficiency Virus (HIV) (HIV1/2
antibodies).

6. Subjects who are known to be positive for Hepatitis B antigen (HBsAg) or Hepatitis B
virus (HBV) DNA or Hepatitis C antibody or RNA. Active Hepatitis C is defined by a
known positive Hep C Ab result and known quantitative HCV RNA results greater than the
lower limits of detection of the assay.

7. Subject has a diagnosis of immunodeficiency or is receiving chronic systemic steroid
therapy (in dosing exceeding 10 mg/day of prednisone or equivalent) or any other form
of immunosuppressive therapy within 7 days prior to the first dose of study drug. The
use of physiologic doses of corticosteroids may be approved after consultation with
the Sponsor.

8. Subjects who have received a live-virus vaccination within 30 days of the first dose
of treatment. Seasonal flu vaccines that do not contain live virus are permitted.

9. Subject has severe hypersensitivity (≥Grade 3) to pembrolizumab or other anti-PD-1
monoclonal antibody therapy and/or any of its excipients.

10. Subjects who have received transfusion of blood products (including platelets or red
blood cells) or colony stimulating factors (including G-CSF, GM-CSF or recombinant
erythropoietin) within 3 weeks prior to study Cycle 1, Day 1 (Baseline).

11. Subject has a history of (non-infectious) pneumonitis that required steroids or
current pneumonitis.

12. Subject has a history of interstitial lung disease.

13. Subject has an active infection requiring systemic therapy.

14. Subject has a history or current evidence of any condition, therapy, or laboratory
abnormality that might confound the results of the study, interfere with the subject's
participation for the full duration of the study, or is not in the best interest of
the subject to participate, in the opinion of the treating Investigator.

15. Subject has not recovered (i.e., ≤ Grade 1 or at Baseline) from adverse events (AEs)
due to a previously administered agent.

16. Participation in another clinical study of an investigational anti-cancer agent or has
used an investigational device within 30 days of screening.

17. Subject has known psychiatric or substance abuse disorders that would interfere with
the subject's ability to cooperate with the requirements of the study.

18. Subjects who are pregnant or breastfeeding or expecting to conceive children within
the projected duration of the study, starting with the Screening visit through 120
days after the last dose of study treatment.