Moving Forward: Advantages and Challenges of Closed-Loop Control for Cell-Based Therapies

Guy-Bart Stan Control Engineering Synthetic Biology Group Centre for Synthetic Biology and Innovation

Department of Bioengineering Imperial College London g.stan@imperial.ac.uk

Funded by EPSRC projects EP/K020781/1 and EP/K020617/1 “In vivo integral feedback control for robust synthetic biology”

Synthetic Biology = (Control) Engineering Biology

Society&

Industry

AcademicResearch

Systems & ControlEngineering

SyntheticBiology

Research in my group:“Control Engineering

Synthetic Biology”

K

Gcontrolengineering

syntheticbiology

Goal: Engineer cells that autonomously and reliably perform useful tasks, with applications to biotechnology and cell-based medicine

Problem: Depending on the target application, engineered cells must operate in changing and uncertain conditions/contexts

Solution: Design of biomolecular feedback control mechanisms that enable robust performance of engineered cells

Improving the Robust Performance of Engineered Cells

Examples of Man-Made Systems with Robust Performance

Fly-by-wire planes Advanced autonomous robots

Autonomous trains

How is this achieved?

Self-driving cars

reference

sensing

compu-ngactua-ng

temperature

reference-measuredtemp

Performance Despite Uncertainties and Perturbations

The Feedback (Closed-Loop) Control Paradigm

reference outputSystemActuatorController

Sensor

“FeedbackControlParadigm”

controlerror=

reference-measuredoutput

The Feedback (Closed-Loop) Control Paradigm

reference concentra-onExtracellular

EnvironmentActuatorController

Sensor

Cell

“FeedbackControlParadigm”

Closed-Loop Control by Engineered Cells Cells that Maintain Homeostasis

Goal: Engineer (populations of) cells that autonomously, reliably and safely:• Monitor the status of their surrounding environment (diagnosis)• Produce, locally and on-demand, specific molecules (treatment)• Continuously check and adjust the performance of their action (closed-loop)

(automatic correction of error between desired and actual values)

Cell

EngineeredControl System

sensingresponse

actuation molecule(drug, vitamin, nutrient)

environmental (control) variable

Closed-Loop Control by Engineered Cells Examples

Goal: Engineer (populations of) cells that autonomously, reliably and safely:• Monitor the status of their surrounding environment (diagnosis)• Produce, locally and on-demand, specific molecules (treatment)• Continuously check and adjust the performance of their action (closed-loop)

(automatic correction of error between desired and actual values)

Theranostics for personalised medicine Kojima, Aubel and Fussenegger 33

Figure 3

(a)

(b)

(c)

Construction of sensor modulefor diagnosis

An

80S

DNA

RNA

Functional Protein

Promoter pARegulator/ Sensor

Promoter pATherapeutic

gene

Synthetic gene circuitto connect diagnostic input &

therapeutic output

Pathologic metabolite

Engineering of cells fromthe patient

&Direct implantation

Engineering of other cells &

Implantation with microencapsulation

Blood vessel

Urate

Allantoin

PhCMV URAT1 pA

URAT1

PSV40 smUOX pA

huc08

PUREX8

PhEF1 KRAB-mHucR pA

mHucRKRAB

smUOX

Pathologicurate level

Lowurate level

Convert urate to allatoin

PhCMV pA

+1

TtgR-PPAR

TtgR

PPARLBD

Lipid -sensing receptor

PhCMVmin

(e.g.Pramlintide)

pAOTtgR

PTtgR1

HT-1080

Transgene

Obeseob/ob mice

InputHigh-fat Diet

Blood Fat Sensor

ProcessingIntegration

Coordination

AppetiteSuppression

&Weight Loss

Implant

Pramlintide

Intraperitoneal injection

Hyperlipidemia( )

Pramlintide

Co-repressor complex

Absence of fatty acids

Pramlintide

Co-activator complexPresence of

fatty acids Fatty acid

An

α

TtgR

PPAR

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D

TtgR

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D

Cell microencapsulation

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α

Sensor-effector cell

Current Opinion in Chemical Biology

Engineered mammalian-cell-based theranostic agents. (a) Concept of mammalian-cell-based theranostic agents. By using engineering principles,synthetic biologists can design and reassemble basic biobricks, such as functional DNA, RNA and proteins, in a rational way to achieve bothdiagnostic and therapeutic functions in a single integrated system. This system can be directly in patient-derived cells or other cell lines, which can betransplanted in vivo and regulated to produce therapeutic proteins to treat diseases. (b) Theranostic engineered cells for obesity [37]. A fusion proteincombining the phloretin responsive repressor (TtgR) and the human peroxisome proliferator-activated receptor a (PPARa), which bound a

www.sciencedirect.com Current Opinion in Chemical Biology 2015, 28:29–38

• Cell Therapy to Maintain Uric Acid Homeostasis • Cell Therapy for Graves’ Disease • Cell Therapies for Obesity Control • Cell Therapy for Psoriasis (Martin Fussenegger, ETH Zurich)

Closed-Loop Cell-Based Therapies: “the Cells Will See You Now”

Questions: •How useful might bacterial cell-based therapies that involve feedback

regulation be? For what purposes? •How could they be translated into commercially viable medical products that

deliver real benefits to patients?

1. How useful might bacterial cell-based therapies that involve feedback regulation be? For what purposes?

• What are the advantages? What are the disadvantages? • Which medical/health conditions might they be most useful for? Why?• How does this therapeutic approach compare to other existing or potential approaches?• Who should decide and on what basis?

2. How could they be translated into commercially viable medical products that deliver real benefits to patients? Consider:

• Technical aspects; • Regulatory aspects; and • Social & economic aspects (including Health Technology Assessments)

In each case:• What is the current status? What are the hurdles? How could they be addressed?

By whom?• What is the timescale from prototyping in the lab, to clinical trials, to access to therapies for

people who need them?

Closed-Loop Cell-based Therapies: Suggested Questions for Discussion

• What are the best indications for the first clinical applications, balancing risk / benefit?

• How to do preclinical modelling of closed-loop therapies in vitro and animals?

• How to characterise the pharmacodynamics / pharmacokinetics of closed-loop therapies?

• How to quality-control the manufacturing of closed-loop therapies?

• How to monitor the in vivo performance of closed-loop therapies when introduced into patients?

• How to measure the long-term durability of closed-loop therapies?

• How to incorporate safeguards or external control over closed-loop therapies?

• How does this fit into existing regulatory frameworks? Do these make sense?

• When in the process does environmental risk assessment come into play?

• How are fecal transplants regulated?

Closed-Loop Cell-based Therapies: Questions for Clinical Use