Known allergy to eggs 5. Any uncontrolled intercurrent illness or active ongoing infection that, in the opinion of the physician- investigator, would put the subject at additional risk DC Vaccine for Colorectal Cancer Page 11 of 34 Version 7.11-11-2021 CONFIDENTIAL This protocol is the property of the University of Pennsylvania. Do not disclose or use except as authorized in writing by the study spons or. 4.0 REGISTRATION Assignment of subject numbers will occur at consent and will be in ascending order (16218-01, 16218-02, etc). No numbers will be omitted. This subject identification number will be used as the primary identifier for that subject throughout his/her participation in the trial. Once assigned, the Subject Number must not be reused for any other subject and the Subject Number for that individual must not be changed, even if the subject is re- screened . At the time a subject consents to participate in this study, a Consent Notification Form should be completed. When eligibility of the subject is confirmed by a physician -investigator, an Enrollment Notification should be completed. Both completed forms should be emailed in real- time to : Protocol Monitor and Sponsor Project Manager Center for Cellular Immunotherapies (CCI) Once subject eligibility has been confirmed by a physician -investigator, apheresis collection and the manufacturing of the study vac cine may commence. 5.0 SUBJECT RECRUITMENT AND SCREENING Approximately 12 evaluable subjects will be enrolled in this study. All subjects who receive at least one Dendritic Cell Vaccine at the minimum acceptable dose for infusion will be considered evaluable for primary endpoint analysis. Subjects who fail apheresis or who do not receive a vaccine infusion for any other reasons will not be considered evaluable and will be replaced. Subjects will be identified through the clinical practices of the investigator or sub- investigators and through referrals from outside hospitals and physicians. The study will be posted on clinicaltrials.gov, and publicized via University of Pennsylvania or Abramson Cancer Center press releases. No direct -to-patient advertising will be performed. Female subjects of reproductive potential (women who have reached menarche or women who have not been post -menopausal for at least 24 consecutive months, i.e., who have had menses within the preceding 24 months, or have not undergone a sterilization procedure [hysterectomy or bilateral oophorectomy]) must have negative pregnancy test performed at the time of enrollment and within 30 days of the subject’s 1st DC vaccine (Day 1). Subjects must agree not to participate in a conception process while participating in this study (e.g., active attempt to become pregnant or to impregnate, sperm donation, in v itro fertilization). Additionally, if participating in sexual activity that could lead to pregnancy, the study subject must agree to use at least one reliable method of contraception during their participation in the study. Acceptable birth control includ es one of the following methods: • Total abstinence (no sexual relations) • Female sterilization - surgical removal of both ovaries (woman's reproductive system that stores and releases eggs for fertilization and produces female sex hormones), or tubal ligation (having your “tubes tied”) at least six weeks prior to signing this con sent. • Male sterilization (i.e. vasectomy) • Condoms (male or female) with or without a spermicidal agent • Diaphragm or cervical cap with spermicide DC Vaccine for Colorectal Cancer Page 14 of 34 Version 7.11-11-2021 CONFIDENTIAL This protocol is the property of the University of Pennsylvania. Do not disclose or use except as authorized in writing by the study spons or. Minimum acceptable dose for infusion is 1.00 x 106 DC per peptide. Two doses will be administered approximately 6 weeks apart. Please see Section 8 .3 for additional details. 7.1.9 Potential Toxicities Please refer to the Investigator Brochure for toxicity information. 7.1.10 Return or Destruction of Study Drug The investigational product may need to be returned to the manufacturing facility for a variety of reasons, including but not limited to: 1) Mislabeled product; 2) Condition of subject prohibits infusion/injection, and 3) Subject refuses infusion. Any unus ed product will be returned to CVPF for freezing by CVPF personnel. Final disposition of the investigational product must be documented appropriately. 7.2 Cyclophosphamide 7.2.1 Agent Description Cyclophosphamide is an FDA -approved chemotherapeutic agent. Cyclophosphamide is considered an investigational agent on this protocol since it is not used in accordance with its approved labeling. However, while administered for research purposes as part of this study, it will be prepared and infused in accordance with the FDA approved package insert . Full details on its mechanisms of action and toxicity profile can be found in the package insert. 7.2.2 Receipt and Storage Commercial cyclophosphamide will be obtained through the site -designated research pharmacy for research purposes. It will be stored according to the manufacturing instructions in the approved package insert. 7.2.3 Premedication All subjects receiving cyclophosphamide may be premedicated with an anti-emetic. The choice of premedication will be left to discretion of the treating physician. Cyclophosphamide is associated with moderate to high emetic potential, and antiemetics are recommended to prevent nausea and vomiting. Combining NK1R antagonist (e.g. aprepitant or fosaprepitant) with 5- HT3 receptor antagonist (e.g. ondansetron) is recommended, but may be modified per investigator discretion and institutional standards. Glucocorticoids (e.g. dexamethasone) should be avoided as these agents may affect vaccine efficacy. 7.2.4 Admin istration A single dose of 300 mg/m2 cyclophosphamide will be administered via intravenous infusion 3 days (+/- 1 day) prior to the first DC Vaccine. DC Vaccine for Colorectal Cancer Page 15 of 34 Version 7.11-11-2021 CONFIDENTIAL This protocol is the property of the University of Pennsylvania. Do not disclose or use except as authorized in writing by the study spons or. 7.2.5 Potential Toxicities Please refer to the cyclophosphamide package insert for toxicity information. The package insert describes the risks of cyclophosphamide when given as part of routine care. We expect similar side effects when administered as part of this study. 8.0 STUDY PROCEDURES 8.1 Dendritic Cell (mDC3/8) Preparation After eligibility has been confirmed by a physician -investigator , subjects will undergo a large volume apheresis procedure (approximately 15 -20 L volume) at the HUP Apheresis Unit according to standard procedures for autologous transplantation, to allow for a target of 1 -2x1010 mononuclear cells to be collected . The actual volume apheresis procedure to be performed will be at the discretion of the physician -investigator in consultation with transfusion medicine. Apheresis may occur any time after physic ian-investigator confirmation of eligibility but must occur at least 7 days prior to the anticipated vaccination. The apheresis product will be transported to the CVPF manufacturing facility and manufactured in accordance with the current mDC3/8 Investigat or’s Brochure. If the initial apheresis collection does not yield an adequate number of cells required for manufacturing all required DC Vaccines, the second study apheresis procedure (performed after last DC Vaccine) may be moved up to an earlier study timepoint to allow for required manufacturing. An approximate 15 liter volume procedure will be performed, and the product processed as indicated in the Investigator’s Brochure. Cells remaining after manufacturing is complete may be banked for research purposes. 8.2 Treg Depletion Subjects will return to the Hospital of the University of Pennsylvania to receive a single dose of IV Cyclophosphamide ( 300 mg/m2) -3 days (+/- 1 day) prior to DC Vaccine #1, in order to deplete circulating Treg cells prior to priming vaccination. Subjects may receive premedication at the discretion of the treating physician. Only a single dose of cyclophosphamide is given to each subject during the initial treatment phase prior to DC Vaccine #l. 8.3 Administration of Dendritic Cell Vaccines (mDC3/8 vaccines with and without influenza) A total of 3 DC vaccines will be administered over a ~12- week period with priming DC Vaccine #1 administered on Day 1, followed by booster DC Vaccine #2 and DC Vaccine #3 administered ~6 weeks apart . Vaccines cannot be administered until all toxicities ≥ grade 2 have resolved to baseline. All infusions will take place at the Hospital of the University of Pennsylvania by a licensed Registered Nurse. Each DC vaccine is administered by intravenous infusion through either a peripheral venous line or a central venous line. A macrodrip intravenous tubing will be used to infuse DC vaccine by gravity (i.e. no infusion pump will be used), therefore each infus ion will take less than 15 minutes. All subjects will have vital signs (including temperature, respiration rate, pulse, blood pressure, oxygen saturation) assessed prior to each infusion. After the first infusion, subjects will be observed for 2 hours post-infusion, with vital signs assessed every 30 minutes (+/ - 5 minutes) from the end DC Vaccine for Colorectal Cancer Page 16 of 34 Version 7.11-11-2021 CONFIDENTIAL This protocol is the property of the University of Pennsylvania. Do not disclose or use except as authorized in writing by the study spons or. of the infusion. After each subsequent infusion, subjects will be observed for 30 minutes after the end of the infusion, with vital signs assessed at 30 minutes (+/ - 5 minutes) post-infusion. If subjects develop temperature greater than 38ºC, acetaminophen 650mg PO should be given and the PI notified the same day. After the required observation period is complete, subjects may be discharged to home from the treatment area. Administration of the DC v accine may be delayed for a number of reasons, including toxicity, investigator discretion, etc. Treatment delays of up to 21 days will be allowed. If administration of the next planned dose is delayed greater than 21 days, the subject will discontinue the study vaccine and will not be eligible to receive additional treatment on this protocol. Treatment delays should be to be kept to a minimum and every effort is to be made to maintain a planned schedule. 8.4 Immune Monitoring Research blood samples for immu ne monitoring will be collected in accordance with the Study Calendar in Section 10.0. This testing requires five 10mL green top tubes (BD vacutainer sodium heparin tube ) for a total of ~50 ml of blood. These blood sampl es will be used for immunologic monitoring studies (e.g. IFN -y ELIspot, peptide- HLA (p -HLA) multimer staining and cytotoxicity assays). The blood samples will be transported to Dr. Carreno’s laboratory (SPE 8 -309, bays 305B - 307B). Subjects will undergo an additional large -volume apheresis procedure (approximately 15 liter volume) ~7 -14 days after their last DC Vaccine to collect lymphocytes for functional laboratory assays, to determi ne immunity against neoantigen peptides and TCR sequencing . Note: As per Section 8.1 above, this apheresis collection may be moved up to an earlier study time point if deemed necessary for manufacturing purposes. This additional apheresis procedure will be performed at the HUP Apheresis Unit according to standard procedures . These cells will then be transported to Dr. Carreno’s laboratory for processing , storage, and exploratory analysis. 8.4.1 Flow Cytometry / p- HLA multimer Staining Assessment of cellular immune activity may occur via the application of flow cytometry. Flow cytometric assays will include an examination of the influence of immunotherapy on the ability of subject T cells to exhibit phenotypic markers associated with cytolytic potential (e.g. IFN -y, IL -2, TNF -alpha, Granzyme B) after short -term stimulation by mutated peptide and p -HLA multimer staining. PBMC responses against a pool of known antigenic Cytomegalovirus, Epstein Barr Virus and Influenza epitopes will be evaluated in order to track general cellular immune competence during the study. 8.4.2 Cytotoxicity A ssays The cytolytic activity of neoantigen -specific T cells will be assessed by chromium release cytotoxicity assays. Target cells are co -cultured in the presence of CD8+ T cells isolated from vaccinated subjects. Cytotoxicity will be measured of Cr release from lysed target cells. When available, HLA class I matched tumor cell lines will be used as the target cell population. DC Vaccine for Colorectal Cancer Page 17 of 34 Version 7.11-11-2021 CONFIDENTIAL This protocol is the property of the University of Pennsylvania. Do not disclose or use except as authorized in writing by the study spons or. 8.4.3 TCR Sequencing TCR sequencing will be performed as previously described. Briefly, single -cell sorting will be performed on tetrame r-positive cells identified from apheresis collection 7 -14 days following last DC Vaccine. RT -PCR will be performed to provide template DNA for PCR - based TCR gene amplification. PCR products with then be gel purified and sequenced. The functionality of TCR sequences will then be confirmed by cloning into an expression vector for transduction of human T cells for in vitro assays. 8.5 Post-DC Vaccine Surveillance Following the End of Study Treatment visit, subjects will continue to be followed for safety and the collection of immune monitoring samples for up to 1 year post-DC Vaccine #1. The first Post - DC Vaccine Surveillance Visit will occur approximately 6 months after DC Vaccine #1. During Post -DC Vaccine Surveillance, only protocol‐defined adverse even ts (PDAEs) will be collected and reported. This includes any adverse events that are ongoing at the End of Treatment Visit as well as any adverse events determined to be at least possibly related to the investigational product (See Section 12.1) . Blood samples will continue to be collected for immune monitoring analysis every 3 months as per the Study Calendar in Section 10.0. Tissue samples obtained as part of stand ard of care procedures may also be used for research analysis. Subjects will not be formally followed for response, however if the subject experiences documented disease recurrence during Post -DC Vaccine Surveillance, this data will be collected for research purposes. In the event that a subject cannot return to the University of Pennsylvania for follow -up visits, the subject’s local provider may also be asked to provide information from the subject’s medical record and assist in the collection of protocol -required immune monitoring blood samples , which will be sent to the University of Pennsylvania Carreno Lab . 9.0 POTENTIAL TOXICITY AND DOSE MODIFICATIONS All adverse events should be recorded and reported as per protocol Section 12 . Any toxicities of grade 2 or higher , regardless of attribution/expectedness, should be reported immediately to the Principal Investigator . Additional vaccines cannot be administered until all toxicities ≥ grade 2 have resolved to baseline. 9.1 Dose Limiting Toxicity (DLT) Is defined as any of the below events determined to be at least possibly related to the dendritic cell vaccines (mDC3/8 vaccine ): • Any Grade 3 or greater hematological and non-hematological toxicities • Any Grade 3 or greater allergic reaction • Any Grade 3 or greater autoimmunity that involves vital organ (heart, kidneys, brain, eye, liver, colon or adrenal gland) DC Vaccine for Colorectal Cancer Page 18 of 34 Version 7.11-11-2021 CONFIDENTIAL This protocol is the property of the University of Pennsylvania. Do not disclose or use except as authorized in writing by the study spons or. If a subject experiences a DLT, they will be discontinued from additional study treatment. Subjects discontinued from study treatment due to a DLT will continue to be followed per the Study Calendar in Section 10.0 until the End of Study visit and for adverse events per Section 12.1. Dose -limiting toxicities will be confirmed by the Sponsor Medical Director . The Medical Director will also assess the impact of dose- limiting toxicities on subsequent enrollment/treatment activity. Please refer to Section 12.7 for study stopping rules. DC Vaccine for Colorectal Cancer Page 21 of 34 Version 7.11-11-2021 CONFIDENTIAL This protocol is the property of the University of Pennsylvania. Do not disclose or use except as authorized in writing by the study spons or.